How to update an object in a List in C

Question

I have a List lt  gt  of custom objects   I need to find an object in this list by some property which is unique and update another property of this object    What is the quickest way to do it

User · Answer

You can do somthing like    if  product    null        var products   Repository Products      var indexOf   products IndexOf products Find p   gt  p Id    product Id        Repository Products indexOf    product         or      Repository Products indexOf  prop   product prop

User · Answer

This was a new discovery today - after having learned the class struct reference lesson   You can use Linq and  Single  if you know the item will be found  because Single returns a variable     myList Single x   gt  x MyProperty    myValue  OtherProperty   newValue

User · Answer

Can also try     lstProductDetail Where S   gt  S ProductID                 Select S   gt    S ProductPcs    Update Value    return S     ToList

User · Answer

Just to add to CKoenig s response  His answer will work as long as the class you re dealing with is a reference type  like a class   If the custom object were a struct  this is a value type  and the results of  FirstOrDefault will give you a local copy of that  which will mean it won t persist back to the collection  as this example shows   struct MyStruct       public int TheValue   get  set        Test code   List lt MyStruct gt  coll   new List lt MyStruct gt                                                new MyStruct  TheValue   10                                               new MyStruct  TheValue   1                                               new MyStruct  TheValue   145                                                  var found   coll FirstOrDefault c   gt  c TheValue    1   found TheValue   12   foreach  var myStruct in coll        Console WriteLine myStruct TheValue     Console ReadLine      The output is 10 1 145  Change the struct to a class and the output is 10 12 145  HTH

User · Answer

Using Linq to find the object you can do   var obj   myList FirstOrDefault x   gt  x MyProperty    myValue   if  obj    null  obj OtherProperty   newValue    But in this case you might want to save the List into a Dictionary and use this instead          define after getting the List Enumerable whatever var dict   myList ToDictionary x   gt  x MyProperty          somewhere in code MyObject found  if  dict TryGetValue myValue  out found   found OtherProperty   newValue

User · Answer

or without linq  foreach MyObject obj in myList       if obj prop    someValue            obj otherProp   newValue       break

User · Answer

var itemIndex   listObject FindIndex x   gt  x    SomeSpecialCondition     var item   listObject ElementAt itemIndex   item SomePropYouWantToChange    yourNewValue

[c#] How to update an object in a List<> in C#

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