Update all objects in a collection using LINQ

Question

Is there a way to do the following using LINQ   foreach  var c in collection        c PropertyToSet   value      To clarify  I want to iterate through each object in a collection and then update a property on each object   My use case is I have a bunch of comments on a blog post  and I want to iterate through each comment on a blog post and set the datetime on the blog post to be  10 hours  I could do it in SQL  but I want to keep it in the business layer

User · Answer

No  LINQ doesn t support a manner of mass updating  The only shorter way would be to use a ForEach extension method - Why there is no ForEach extension method on IEnumerable

User · Answer

Use   ListOfStuff Where w   gt  w Thing    value  ToList   ForEach f   gt  f OtherThing   vauleForNewOtherThing     I am not sure if this is overusing LINQ or not  but it has worked for me when wanting to update a specific items in the list for a specific condition

User · Answer

Although you specifically asked for a LINQ solution and this question is quite old I post a non-LINQ-solution  This is because LINQ     language integrated query  is meant to be used for queries on collections  All LINQ-methods don   t modify the underlying collection  they just return a new one  or more precise an iterator to a new collection   Thus whatever you do e g  with a Select doesn   t effect the underlying collection  you simply get a new one   Of course you could do it with a ForEach  which isn t LINQ  by the way  but an extension on List lt T gt    But this literally uses foreach anyway  but with a lambda-expression  Apart from this every LINQ method internally iterates your collection e g  by using foreach or for  however it simply hides it from the client  I don   t consider this any more readable nor maintainable  think of edit your code while debugging a method containing lambda-expressions    Having said this shouldn t use LINQ to modify items in your collection  A better way is the solution you already provided in your question  With a classic loop you can easily iterate your collection and update its items  In fact all those solutions relying on List ForEach are nothing different  but far harder to read from my perspective   So you shouldn t use LINQ in those cases where you want to update the elements of your collection

User · Answer

Here is the extension method I use              lt summary gt          Executes an Update statement block on all elements in an  IEnumerable of T         sequence           lt  summary gt           lt typeparam name  TSource  gt The source element type  lt  typeparam gt           lt param name  source  gt The source sequence  lt  param gt           lt param name  action  gt The action method to execute for each element  lt  param gt           lt returns gt The number of records affected  lt  returns gt      public static int Update lt TSource gt  this IEnumerable lt TSource gt  source  Func lt TSource gt  action                if  source    null  throw new ArgumentNullException  source            if  action    null  throw new ArgumentNullException  action            if  typeof  TSource  IsValueType              throw new NotSupportedException  value type elements are not supported by update              var count   0          foreach  var element in source                        action element               count                      return count

User · Answer

While you can use a ForEach extension method  if you want to use just the framework you can do  collection Select c   gt   c PropertyToSet   value  return c    ToList      The ToList is needed in order to evaluate the select immediately due to lazy evaluation

User · Answer

Suppose we have data like below   var items   new List lt string gt    123    456    789        Like 123 value get updated to 123ABC      and if we want to modify the list and replace the existing values of the list to modified values  then first create a new empty list  then loop through data list by invoking modifying method on each list item   var modifiedItemsList   new List lt string gt      items ForEach i   gt      var modifiedValue   ModifyingMethod i     modifiedItemsList Add items AsEnumerable   Where w   gt  w    i  Select x   gt  modifiedValue  ToList   FirstOrDefault    ToString            assign back the modified list items   modifiedItemsList

User · Answer

You can use Magiq  a batch operation framework for LINQ

User · Answer

I am doing this  Collection All c   gt    c needsChange   value  return true

User · Answer

My 2 pennies -   collection Count v   gt   v PropertyToUpdate   newValue     null

User · Answer

There is no built-in extension method to do this   Although defining one is fairly straight forward   At the bottom of the post is a method I defined called Iterate   It can be used like so  collection Iterate c   gt    c PropertyToSet   value        Iterate Source  public static void Iterate lt T gt  this IEnumerable lt T gt  enumerable  Action lt T gt  callback        if  enumerable    null                throw new ArgumentNullException  enumerable               IterateHelper enumerable   x  i    gt  callback x       public static void Iterate lt T gt  this IEnumerable lt T gt  enumerable  Action lt T int gt  callback        if  enumerable    null                throw new ArgumentNullException  enumerable               IterateHelper enumerable  callback      private static void IterateHelper lt T gt  this IEnumerable lt T gt  enumerable  Action lt T int gt  callback        int count   0      foreach  var cur in enumerable                callback cur  count           count

User · Answer

I wrote some extension methods to help me out with that    namespace System Linq            lt summary gt          Class to hold extension methods to Linq           lt  summary gt      public static class LinqExtensions                    lt summary gt              Changes all elements of IEnumerable by the change function              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  change  gt The way you want to change the stuff lt  param gt               lt returns gt An IEnumerable with all changes applied lt  returns gt          public static IEnumerable lt T gt  Change lt T gt  this IEnumerable lt T gt  enumerable  Func lt T  T gt  change                          ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace change   change                 foreach  var item in enumerable                                yield return change item                                         lt summary gt              Changes all elements of IEnumerable by the change function  that fullfill the where function              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  change  gt The way you want to change the stuff lt  param gt               lt param name  where  gt The function to check where changes should be made lt  param gt               lt returns gt              An IEnumerable with all changes applied              lt  returns gt          public static IEnumerable lt T gt  ChangeWhere lt T gt  this IEnumerable lt T gt  enumerable                                                       Func lt T  T gt  change                                                      Func lt T  bool gt   where                        ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace change   change                ArgumentCheck IsNullorWhiteSpace  where   where                 foreach  var item in enumerable                                if   where item                                         yield return change item                                     else                                       yield return item                                                          lt summary gt              Changes all elements of IEnumerable by the change function that do not fullfill the except function              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  change  gt The way you want to change the stuff lt  param gt               lt param name  where  gt The function to check where changes should not be made lt  param gt               lt returns gt              An IEnumerable with all changes applied              lt  returns gt          public static IEnumerable lt T gt  ChangeExcept lt T gt  this IEnumerable lt T gt  enumerable                                                       Func lt T  T gt  change                                                       Func lt T  bool gt   where                        ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace change   change                ArgumentCheck IsNullorWhiteSpace  where   where                 foreach  var item in enumerable                                if    where item                                         yield return change item                                     else                                       yield return item                                                          lt summary gt              Update all elements of IEnumerable by the update function  only works with reference types               lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  update  gt The way you want to change the stuff lt  param gt               lt returns gt              The same enumerable you passed in              lt  returns gt          public static IEnumerable lt T gt  Update lt T gt  this IEnumerable lt T gt  enumerable                                                 Action lt T gt  update  where T   class                       ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace update   update                foreach  var item in enumerable                                update item                             return enumerable                          lt summary gt              Update all elements of IEnumerable by the update function  only works with reference types              where the where function returns true              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  update  gt The way you want to change the stuff lt  param gt               lt param name  where  gt The function to check where updates should be made lt  param gt               lt returns gt              The same enumerable you passed in              lt  returns gt          public static IEnumerable lt T gt  UpdateWhere lt T gt  this IEnumerable lt T gt  enumerable                                                 Action lt T gt  update  Func lt T  bool gt  where  where T   class                       ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace update   update                foreach  var item in enumerable                                if  where item                                         update item                                               return enumerable                          lt summary gt              Update all elements of IEnumerable by the update function  only works with reference types              Except the elements from the where function              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  update  gt The way you want to change the stuff lt  param gt               lt param name  where  gt The function to check where changes should not be made lt  param gt               lt returns gt              The same enumerable you passed in              lt  returns gt          public static IEnumerable lt T gt  UpdateExcept lt T gt  this IEnumerable lt T gt  enumerable                                                 Action lt T gt  update  Func lt T  bool gt  where  where T   class                       ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace update   update                 foreach  var item in enumerable                                if   where item                                         update item                                               return enumerable                      I am using it like this           List lt int gt  exampleList   new List lt int gt                                  1  2   3                           2   3   4         var updated1   exampleList Change x   gt  x   1              10  2  3         var updated2   exampleList              ChangeWhere    changeItem   gt  changeItem   10              change you want to make                             conditionItem   gt  conditionItem  lt  2         where you want to make the change            1  0  0         var updated3   exampleList              ChangeExcept changeItem   gt  0                             Change elements to 0                           conditionItem   gt  conditionItem    1         everywhere but where element is 1   For reference the argument check        lt summary gt      Class for doing argument checks      lt  summary gt  public static class ArgumentCheck              lt summary gt          Checks if a value is string or any other object if it is string         it checks for nullorwhitespace otherwhise it checks for null only          lt  summary gt           lt typeparam name  T  gt Type of the item you want to check lt  typeparam gt           lt param name  item  gt The item you want to check lt  param gt           lt param name  nameOfTheArgument  gt Name of the argument lt  param gt      public static void IsNullorWhiteSpace lt T gt  T item  string nameOfTheArgument                      Type type   typeof T           if  type    typeof string                 type    typeof String                         if  string IsNullOrWhiteSpace item as string                                 throw new ArgumentException nameOfTheArgument     is null or Whitespace                                    else                       if  item    null                                throw new ArgumentException nameOfTheArgument     is null

User · Answer

While you can use a ForEach extension method  if you want to use just the framework you can do  collection Select c   gt   c PropertyToSet   value  return c    ToList      The ToList is needed in order to evaluate the select immediately due to lazy evaluation

User · Answer

There is no built-in extension method to do this   Although defining one is fairly straight forward   At the bottom of the post is a method I defined called Iterate   It can be used like so  collection Iterate c   gt    c PropertyToSet   value        Iterate Source  public static void Iterate lt T gt  this IEnumerable lt T gt  enumerable  Action lt T gt  callback        if  enumerable    null                throw new ArgumentNullException  enumerable               IterateHelper enumerable   x  i    gt  callback x       public static void Iterate lt T gt  this IEnumerable lt T gt  enumerable  Action lt T int gt  callback        if  enumerable    null                throw new ArgumentNullException  enumerable               IterateHelper enumerable  callback      private static void IterateHelper lt T gt  this IEnumerable lt T gt  enumerable  Action lt T int gt  callback        int count   0      foreach  var cur in enumerable                callback cur  count           count

User · Answer

Suppose we have data like below   var items   new List lt string gt    123    456    789        Like 123 value get updated to 123ABC      and if we want to modify the list and replace the existing values of the list to modified values  then first create a new empty list  then loop through data list by invoking modifying method on each list item   var modifiedItemsList   new List lt string gt      items ForEach i   gt      var modifiedValue   ModifyingMethod i     modifiedItemsList Add items AsEnumerable   Where w   gt  w    i  Select x   gt  modifiedValue  ToList   FirstOrDefault    ToString            assign back the modified list items   modifiedItemsList

User · Answer

You can use LINQ to convert your collection to an array and then invoke Array ForEach     Array ForEach MyCollection ToArray    item  gt item DoSomeStuff       Obviously this will not work with collections of structs or inbuilt types like integers or strings

User · Answer

I assume you want to change values inside a query so you could write a function for it  void DoStuff         Func lt string  Foo  bool gt  test    y  x    gt    x Bar   y  return true         List lt Foo gt  mylist   new List lt Foo gt         var v   from x in mylist             where test  value   x              select x     class Foo       string Bar   get  set        But not shure if this is what you mean

User · Answer

I actually found an extension method that will do what I want nicely public static IEnumerable lt T gt  ForEach lt T gt       this IEnumerable lt T gt  source      Action lt T gt  act        foreach  T element in source  act element       return source

User · Answer

My 2 pennies -   collection Count v   gt   v PropertyToUpdate   newValue     null

User · Answer

I actually found an extension method that will do what I want nicely public static IEnumerable lt T gt  ForEach lt T gt       this IEnumerable lt T gt  source      Action lt T gt  act        foreach  T element in source  act element       return source

User · Answer

I am doing this  Collection All c   gt    c needsChange   value  return true

User · Answer

You can use Magiq  a batch operation framework for LINQ

User · Answer

Here is the extension method I use              lt summary gt          Executes an Update statement block on all elements in an  IEnumerable of T         sequence           lt  summary gt           lt typeparam name  TSource  gt The source element type  lt  typeparam gt           lt param name  source  gt The source sequence  lt  param gt           lt param name  action  gt The action method to execute for each element  lt  param gt           lt returns gt The number of records affected  lt  returns gt      public static int Update lt TSource gt  this IEnumerable lt TSource gt  source  Func lt TSource gt  action                if  source    null  throw new ArgumentNullException  source            if  action    null  throw new ArgumentNullException  action            if  typeof  TSource  IsValueType              throw new NotSupportedException  value type elements are not supported by update              var count   0          foreach  var element in source                        action element               count                      return count

User · Answer

I assume you want to change values inside a query so you could write a function for it  void DoStuff         Func lt string  Foo  bool gt  test    y  x    gt    x Bar   y  return true         List lt Foo gt  mylist   new List lt Foo gt         var v   from x in mylist             where test  value   x              select x     class Foo       string Bar   get  set        But not shure if this is what you mean

User · Answer

My 2 pennies -   collection Count v   gt   v PropertyToUpdate   newValue     null

User · Answer

collection ToList   ForEach c   gt  c PropertyToSet   value

User · Answer

I assume you want to change values inside a query so you could write a function for it  void DoStuff         Func lt string  Foo  bool gt  test    y  x    gt    x Bar   y  return true         List lt Foo gt  mylist   new List lt Foo gt         var v   from x in mylist             where test  value   x              select x     class Foo       string Bar   get  set        But not shure if this is what you mean

User · Answer

I wrote some extension methods to help me out with that    namespace System Linq            lt summary gt          Class to hold extension methods to Linq           lt  summary gt      public static class LinqExtensions                    lt summary gt              Changes all elements of IEnumerable by the change function              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  change  gt The way you want to change the stuff lt  param gt               lt returns gt An IEnumerable with all changes applied lt  returns gt          public static IEnumerable lt T gt  Change lt T gt  this IEnumerable lt T gt  enumerable  Func lt T  T gt  change                          ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace change   change                 foreach  var item in enumerable                                yield return change item                                         lt summary gt              Changes all elements of IEnumerable by the change function  that fullfill the where function              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  change  gt The way you want to change the stuff lt  param gt               lt param name  where  gt The function to check where changes should be made lt  param gt               lt returns gt              An IEnumerable with all changes applied              lt  returns gt          public static IEnumerable lt T gt  ChangeWhere lt T gt  this IEnumerable lt T gt  enumerable                                                       Func lt T  T gt  change                                                      Func lt T  bool gt   where                        ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace change   change                ArgumentCheck IsNullorWhiteSpace  where   where                 foreach  var item in enumerable                                if   where item                                         yield return change item                                     else                                       yield return item                                                          lt summary gt              Changes all elements of IEnumerable by the change function that do not fullfill the except function              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  change  gt The way you want to change the stuff lt  param gt               lt param name  where  gt The function to check where changes should not be made lt  param gt               lt returns gt              An IEnumerable with all changes applied              lt  returns gt          public static IEnumerable lt T gt  ChangeExcept lt T gt  this IEnumerable lt T gt  enumerable                                                       Func lt T  T gt  change                                                       Func lt T  bool gt   where                        ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace change   change                ArgumentCheck IsNullorWhiteSpace  where   where                 foreach  var item in enumerable                                if    where item                                         yield return change item                                     else                                       yield return item                                                          lt summary gt              Update all elements of IEnumerable by the update function  only works with reference types               lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  update  gt The way you want to change the stuff lt  param gt               lt returns gt              The same enumerable you passed in              lt  returns gt          public static IEnumerable lt T gt  Update lt T gt  this IEnumerable lt T gt  enumerable                                                 Action lt T gt  update  where T   class                       ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace update   update                foreach  var item in enumerable                                update item                             return enumerable                          lt summary gt              Update all elements of IEnumerable by the update function  only works with reference types              where the where function returns true              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  update  gt The way you want to change the stuff lt  param gt               lt param name  where  gt The function to check where updates should be made lt  param gt               lt returns gt              The same enumerable you passed in              lt  returns gt          public static IEnumerable lt T gt  UpdateWhere lt T gt  this IEnumerable lt T gt  enumerable                                                 Action lt T gt  update  Func lt T  bool gt  where  where T   class                       ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace update   update                foreach  var item in enumerable                                if  where item                                         update item                                               return enumerable                          lt summary gt              Update all elements of IEnumerable by the update function  only works with reference types              Except the elements from the where function              lt  summary gt               lt param name  enumerable  gt The enumerable where you want to change stuff lt  param gt               lt param name  update  gt The way you want to change the stuff lt  param gt               lt param name  where  gt The function to check where changes should not be made lt  param gt               lt returns gt              The same enumerable you passed in              lt  returns gt          public static IEnumerable lt T gt  UpdateExcept lt T gt  this IEnumerable lt T gt  enumerable                                                 Action lt T gt  update  Func lt T  bool gt  where  where T   class                       ArgumentCheck IsNullorWhiteSpace enumerable   enumerable                ArgumentCheck IsNullorWhiteSpace update   update                 foreach  var item in enumerable                                if   where item                                         update item                                               return enumerable                      I am using it like this           List lt int gt  exampleList   new List lt int gt                                  1  2   3                           2   3   4         var updated1   exampleList Change x   gt  x   1              10  2  3         var updated2   exampleList              ChangeWhere    changeItem   gt  changeItem   10              change you want to make                             conditionItem   gt  conditionItem  lt  2         where you want to make the change            1  0  0         var updated3   exampleList              ChangeExcept changeItem   gt  0                             Change elements to 0                           conditionItem   gt  conditionItem    1         everywhere but where element is 1   For reference the argument check        lt summary gt      Class for doing argument checks      lt  summary gt  public static class ArgumentCheck              lt summary gt          Checks if a value is string or any other object if it is string         it checks for nullorwhitespace otherwhise it checks for null only          lt  summary gt           lt typeparam name  T  gt Type of the item you want to check lt  typeparam gt           lt param name  item  gt The item you want to check lt  param gt           lt param name  nameOfTheArgument  gt Name of the argument lt  param gt      public static void IsNullorWhiteSpace lt T gt  T item  string nameOfTheArgument                      Type type   typeof T           if  type    typeof string                 type    typeof String                         if  string IsNullOrWhiteSpace item as string                                 throw new ArgumentException nameOfTheArgument     is null or Whitespace                                    else                       if  item    null                                throw new ArgumentException nameOfTheArgument     is null

User · Answer

Although you specifically asked for a LINQ solution and this question is quite old I post a non-LINQ-solution  This is because LINQ     language integrated query  is meant to be used for queries on collections  All LINQ-methods don   t modify the underlying collection  they just return a new one  or more precise an iterator to a new collection   Thus whatever you do e g  with a Select doesn   t effect the underlying collection  you simply get a new one   Of course you could do it with a ForEach  which isn t LINQ  by the way  but an extension on List lt T gt    But this literally uses foreach anyway  but with a lambda-expression  Apart from this every LINQ method internally iterates your collection e g  by using foreach or for  however it simply hides it from the client  I don   t consider this any more readable nor maintainable  think of edit your code while debugging a method containing lambda-expressions    Having said this shouldn t use LINQ to modify items in your collection  A better way is the solution you already provided in your question  With a classic loop you can easily iterate your collection and update its items  In fact all those solutions relying on List ForEach are nothing different  but far harder to read from my perspective   So you shouldn t use LINQ in those cases where you want to update the elements of your collection

User · Answer

No  LINQ doesn t support a manner of mass updating  The only shorter way would be to use a ForEach extension method - Why there is no ForEach extension method on IEnumerable

User · Answer

collection ToList   ForEach c   gt  c PropertyToSet   value

User · Answer

There is no built-in extension method to do this   Although defining one is fairly straight forward   At the bottom of the post is a method I defined called Iterate   It can be used like so  collection Iterate c   gt    c PropertyToSet   value        Iterate Source  public static void Iterate lt T gt  this IEnumerable lt T gt  enumerable  Action lt T gt  callback        if  enumerable    null                throw new ArgumentNullException  enumerable               IterateHelper enumerable   x  i    gt  callback x       public static void Iterate lt T gt  this IEnumerable lt T gt  enumerable  Action lt T int gt  callback        if  enumerable    null                throw new ArgumentNullException  enumerable               IterateHelper enumerable  callback      private static void IterateHelper lt T gt  this IEnumerable lt T gt  enumerable  Action lt T int gt  callback        int count   0      foreach  var cur in enumerable                callback cur  count           count

User · Answer

You can use LINQ to convert your collection to an array and then invoke Array ForEach     Array ForEach MyCollection ToArray    item  gt item DoSomeStuff       Obviously this will not work with collections of structs or inbuilt types like integers or strings

User · Answer

I actually found an extension method that will do what I want nicely public static IEnumerable lt T gt  ForEach lt T gt       this IEnumerable lt T gt  source      Action lt T gt  act        foreach  T element in source  act element       return source

User · Answer

I actually found an extension method that will do what I want nicely public static IEnumerable lt T gt  ForEach lt T gt       this IEnumerable lt T gt  source      Action lt T gt  act        foreach  T element in source  act element       return source

User · Answer

You can use LINQ to convert your collection to an array and then invoke Array ForEach     Array ForEach MyCollection ToArray    item  gt item DoSomeStuff       Obviously this will not work with collections of structs or inbuilt types like integers or strings

User · Answer

I ve tried a few variations on this  and I keep going back to this guy s solution   http   www hookedonlinq com UpdateOperator ashx  Again  this is somebody else s solution   But I ve compiled the code into a small library  and use it fairly regularly   I m going to paste his code here  for the off chance that his site blog  ceases to exist at some point in the future    There s nothing worse than seeing a post that says  Here is the exact answer you need   Click  and Dead URL        public static class UpdateExtensions        public delegate void Func lt TArg0 gt  TArg0 element             lt summary gt          Executes an Update statement block on all elements in an IEnumerable lt T gt  sequence           lt  summary gt           lt typeparam name  TSource  gt The source element type  lt  typeparam gt           lt param name  source  gt The source sequence  lt  param gt           lt param name  update  gt The update statement to execute for each element  lt  param gt           lt returns gt The numer of records affected  lt  returns gt      public static int Update lt TSource gt  this IEnumerable lt TSource gt  source  Func lt TSource gt  update                if  source    null  throw new ArgumentNullException  source            if  update    null  throw new ArgumentNullException  update            if  typeof TSource  IsValueType              throw new NotSupportedException  value type elements are not supported by update              int count   0          foreach  TSource element in source                        update element               count                      return count             int count   drawingObjects          Where d   gt  d IsSelected  amp  amp  d Color    Colors Blue           Update e   gt    e Color   Color Red  e Selected   false

User · Answer

While you can use a ForEach extension method  if you want to use just the framework you can do  collection Select c   gt   c PropertyToSet   value  return c    ToList      The ToList is needed in order to evaluate the select immediately due to lazy evaluation

User · Answer

You can use LINQ to convert your collection to an array and then invoke Array ForEach     Array ForEach MyCollection ToArray    item  gt item DoSomeStuff       Obviously this will not work with collections of structs or inbuilt types like integers or strings

User · Answer

My 2 pennies -   collection Count v   gt   v PropertyToUpdate   newValue     null

User · Answer

I ve tried a few variations on this  and I keep going back to this guy s solution   http   www hookedonlinq com UpdateOperator ashx  Again  this is somebody else s solution   But I ve compiled the code into a small library  and use it fairly regularly   I m going to paste his code here  for the off chance that his site blog  ceases to exist at some point in the future    There s nothing worse than seeing a post that says  Here is the exact answer you need   Click  and Dead URL        public static class UpdateExtensions        public delegate void Func lt TArg0 gt  TArg0 element             lt summary gt          Executes an Update statement block on all elements in an IEnumerable lt T gt  sequence           lt  summary gt           lt typeparam name  TSource  gt The source element type  lt  typeparam gt           lt param name  source  gt The source sequence  lt  param gt           lt param name  update  gt The update statement to execute for each element  lt  param gt           lt returns gt The numer of records affected  lt  returns gt      public static int Update lt TSource gt  this IEnumerable lt TSource gt  source  Func lt TSource gt  update                if  source    null  throw new ArgumentNullException  source            if  update    null  throw new ArgumentNullException  update            if  typeof TSource  IsValueType              throw new NotSupportedException  value type elements are not supported by update              int count   0          foreach  TSource element in source                        update element               count                      return count             int count   drawingObjects          Where d   gt  d IsSelected  amp  amp  d Color    Colors Blue           Update e   gt    e Color   Color Red  e Selected   false

User · Answer

No  LINQ doesn t support a manner of mass updating  The only shorter way would be to use a ForEach extension method - Why there is no ForEach extension method on IEnumerable

User · Answer

While you can use a ForEach extension method  if you want to use just the framework you can do  collection Select c   gt   c PropertyToSet   value  return c    ToList      The ToList is needed in order to evaluate the select immediately due to lazy evaluation

User · Answer

There is no built-in extension method to do this   Although defining one is fairly straight forward   At the bottom of the post is a method I defined called Iterate   It can be used like so  collection Iterate c   gt    c PropertyToSet   value        Iterate Source  public static void Iterate lt T gt  this IEnumerable lt T gt  enumerable  Action lt T gt  callback        if  enumerable    null                throw new ArgumentNullException  enumerable               IterateHelper enumerable   x  i    gt  callback x       public static void Iterate lt T gt  this IEnumerable lt T gt  enumerable  Action lt T int gt  callback        if  enumerable    null                throw new ArgumentNullException  enumerable               IterateHelper enumerable  callback      private static void IterateHelper lt T gt  this IEnumerable lt T gt  enumerable  Action lt T int gt  callback        int count   0      foreach  var cur in enumerable                callback cur  count           count

User · Answer

Use   ListOfStuff Where w   gt  w Thing    value  ToList   ForEach f   gt  f OtherThing   vauleForNewOtherThing     I am not sure if this is overusing LINQ or not  but it has worked for me when wanting to update a specific items in the list for a specific condition

User · Answer

No  LINQ doesn t support a manner of mass updating  The only shorter way would be to use a ForEach extension method - Why there is no ForEach extension method on IEnumerable

User · Answer

I assume you want to change values inside a query so you could write a function for it  void DoStuff         Func lt string  Foo  bool gt  test    y  x    gt    x Bar   y  return true         List lt Foo gt  mylist   new List lt Foo gt         var v   from x in mylist             where test  value   x              select x     class Foo       string Bar   get  set        But not shure if this is what you mean

[c#] Update all objects in a collection using LINQ

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