How to update only one field using Entity Framework

Question

Here s the table  Users  UserId UserName Password EmailAddress   and the code    public void ChangePassword int userId  string password     code to update the password

User · Answer

I was looking for same and finally I found the solution

using (CString conn = new CString())
{
    USER user = conn.USERs.Find(CMN.CurrentUser.ID);
    user.PASSWORD = txtPass.Text;
    conn.SaveChanges();
}

believe me it work for me like a charm.

User · Answer

i m using this   entity   public class Thing         Key      public int Id   get  set        public string Info   get  set        public string OtherStuff   get  set        dbcontext   public class MyDataContext   DbContext       public DbSet lt Thing  gt  Things   get  set        accessor code   MyDataContext ctx   new MyDataContext        FIRST create a blank object Thing thing   ctx Things Create        SECOND set the ID thing Id   id      THIRD attach the thing  id is not marked as modified  db Things Attach thing        FOURTH set the fields you want updated  thing OtherStuff    only want this field updated        FIFTH save that thing db SaveChanges

User · Answer

public async Task lt bool gt  UpdateDbEntryAsync TEntity entity  params Expression lt Func lt TEntity  object gt  gt    properties        try               this Context Set lt TEntity gt    Attach entity           EntityEntry lt TEntity gt  entry   this Context Entry entity           entry State   EntityState Modified          foreach  var property in properties              entry Property property  IsModified   true          await this Context SaveChangesAsync            return true            catch  Exception ex                throw ex

User · Answer

Ladislav s answer updated to use DbContext  introduced in EF 4 1   public void ChangePassword int userId  string password        var user   new User     Id   userId  Password   password        using  var db   new MyEfContextName                  db Users Attach user           db Entry user  Property x   gt  x Password  IsModified   true          db SaveChanges

User · Answer

I use ValueInjecter nuget to inject Binding Model into database Entity using following   public async Task lt IHttpActionResult gt  Add CustomBindingModel model       var entity  await db MyEntities FindAsync model Id      if  entity   null  return NotFound        entity InjectFrom lt NoNullsInjection gt  model       await db SaveChangesAsync       return Ok        Notice the usage of custom convention that doesn t update Properties if they re null from server    ValueInjecter v3   public class NoNullsInjection   LoopInjection       protected override void SetValue object source  object target  PropertyInfo sp  PropertyInfo tp                if  sp GetValue source     null  return          base SetValue source  target  sp  tp             Usage   target InjectFrom lt NoNullsInjection gt  source     Value Injecter V2  Lookup this answer   Caveat  You won t know whether the property is intentionally cleared to null OR it just didn t have any value it  In other words  the property value can only be replaced with another value but not cleared

User · Answer

Entity framework tracks your changes on objects that you queried from database via DbContext  For example if you DbContext instance name is dbContext  public void ChangePassword int userId  string password        var user   dbContext Users FirstOrDefault u  gt u UserId    userId        user password   password       dbContext SaveChanges

User · Answer

You have basically two options    go the EF way all the way  in that case  you would   load the object based on the userId provided - the entire object gets loaded update the password field save the object back using the context s  SaveChanges   method    In this case  it s up to EF how to handle this in detail  I just tested this  and in the case I only change a single field of an object  what EF creates is pretty much what you d create manually  too - something like    UPDATE dbo Users SET Password    Password WHERE UserId    UserId    So EF is smart enough to figure out what columns have indeed changed  and it will create a T-SQL statement to handle just those updates that are in fact necessary    you define a stored procedure that does exactly what you need  in T-SQL code  just update the Password column for the given UserId and nothing else - basically executes UPDATE dbo Users SET Password    Password WHERE UserId    UserId  and you create a function import for that stored procedure in your EF model and you call this function instead of doing the steps outlined above

User · Answer

You can tell EF which properties have to be updated in this way   public void ChangePassword int userId  string password      var user   new User   Id   userId  Password   password      using  var context   new ObjectContext ConnectionString           var users   context CreateObjectSet lt User gt         users Attach user       context ObjectStateManager GetObjectStateEntry user         SetModifiedProperty  Password        context SaveChanges

User · Answer

context Users UpdateProperty p   gt  p Id  request UserId  new UpdateWrapper lt User gt                                          Expression   p   gt  p FcmId Value   request FcmId                        await  context SaveChangesAsync cancellationToken    Update Property is an extension method public static void UpdateProperty lt T  T2 gt  this DbSet lt T gt  set  Expression lt Func lt T  T2 gt  gt  idExpression              T2 idValue              params UpdateWrapper lt T gt    updateValues              where T   class  new                         var entity   new T                var attach   set Attach entity               attach Property idExpression  IsModified   false              attach Property idExpression  OriginalValue   idValue              foreach  var update in updateValues                                attach Property update Expression  IsModified   true                  attach Property update Expression  CurrentValue   update Value                           And Update Wrapper is a class public class UpdateWrapper lt T gt                public Expression lt Func lt T  object gt  gt  Expression    get  set            public object Value   get  set

User · Answer

While searching for a solution to this problem  I found a variation on GONeale s answer through Patrick Desjardins  blog   public int Update T entity  Expression lt Func lt T  object gt  gt    properties      DatabaseContext Entry entity  State   EntityState Unchanged    foreach  var property in properties          var propertyName   ExpressionHelper GetExpressionText property       DatabaseContext Entry entity  Property propertyName  IsModified   true        return DatabaseContext SaveChangesWithoutValidation            As you can see  it takes as its second parameter an expression of a   function  This will let use this method by specifying in a Lambda   expression which property to update        Update Model  d  gt d Name     or    Update Model  d  gt d Name  d  gt d SecondProperty  d  gt d AndSoOn       A somewhat similar solution is also given here  https   stackoverflow com a 5749469 2115384    The method I am currently using in my own code  extended to handle also  Linq  Expressions of type ExpressionType Convert  This was necessary in my case  for example with Guid and other object properties  Those were  wrapped  in a Convert   and therefore not handled by System Web Mvc ExpressionHelper GetExpressionText   public int Update T entity  Expression lt Func lt T  object gt  gt    properties        DbEntityEntry lt T gt  entry   dataContext Entry entity       entry State   EntityState Unchanged      foreach  var property in properties                string propertyName               Expression bodyExpression   property Body          if  bodyExpression NodeType    ExpressionType Convert  amp  amp  bodyExpression is UnaryExpression                        Expression operand     UnaryExpression property Body  Operand              propertyName     MemberExpression operand  Member Name                    else                       propertyName   System Web Mvc ExpressionHelper GetExpressionText property                     entry Property propertyName  IsModified   true             dataContext Configuration ValidateOnSaveEnabled   false      return dataContext SaveChanges

User · Answer

Combining several suggestions I propose the following        async Task lt bool gt  UpdateDbEntryAsync lt T gt  T entity  params Expression lt Func lt T  object gt  gt    properties  where T   class               try                       var entry   db Entry entity               db Set lt T gt    Attach entity               foreach  var property in properties                  entry Property property  IsModified   true              await db SaveChangesAsync                return true                    catch  Exception ex                        System Diagnostics Debug WriteLine  UpdateDbEntryAsync exception      ex Message               return false                     called by   UpdateDbEntryAsync dbc  d   gt  d Property1      d   gt  d Property2  d   gt  d Property3  etc  etc      Or by   await UpdateDbEntryAsync dbc  d   gt  d Property1     Or by   bool b   UpdateDbEntryAsync dbc  d   gt  d Property1  Result

User · Answer

public void ChangePassword int userId  string password      var user   new User  Id   userId  Password   password      using  var db   new DbContextName            db Entry user  State   EntityState Added      db SaveChanges

User · Answer

I know this is an old thread but I was also looking for a similar solution and decided to go with the solution  Doku-so provided  I m commenting to answer the question asked by  Imran Rizvi   I followed  Doku-so link that shows a similar implementation   Imran Rizvi s question was that he was getting an error using the provided solution  Cannot convert Lambda expression to Type  Expression       because it is not a delegate type   I wanted to offer a small modification I made to  Doku-so s solution that fixes this error in case anyone else comes across this post and decides to use  Doku-so s solution   The issue is the second argument in the Update method    public int Update T entity  Expression lt Func lt T  object gt  gt    properties      To call this method using the syntax provided     Update Model  d  gt d Name  d  gt d SecondProperty  d  gt d AndSoOn      You must add the  params  keyword in front of the second arugment as so   public int Update T entity  params Expression lt Func lt T  object gt  gt    properties    or if you don t want to change the method signature then to call the Update method you need to add the  new  keyword  specify the size of the array  then finally use the collection object initializer syntax for each property to update as seen below   Update Model  new Expression lt Func lt T  object gt  gt  3    d  gt d Name      d  gt d SecondProperty      d  gt d AndSoOn       In  Doku-so s example he is specifying an array of Expressions so you must pass the properties to update in an array  because of the array you must also specify the size of the array  To avoid this you could also change the expression argument to use IEnumerable instead of an array   Here is my implementation of  Doku-so s solution   public int Update lt TEntity gt  LcmsEntities dataContext  DbEntityEntry lt TEntity gt  entityEntry  params Expression lt Func lt TEntity  object gt  gt    properties       where TEntity  class               entityEntry State   System Data Entity EntityState Unchanged           properties ToList                ForEach  property    gt                                var propertyName   string Empty                  var bodyExpression   property Body                  if  bodyExpression NodeType    ExpressionType Convert                      amp  amp  bodyExpression is UnaryExpression                                        Expression operand     UnaryExpression property Body  Operand                      propertyName     MemberExpression operand  Member Name                                    else                                       propertyName   System Web Mvc ExpressionHelper GetExpressionText property                                      entityEntry Property propertyName  IsModified   true                           dataContext Configuration ValidateOnSaveEnabled   false           return dataContext SaveChanges            Usage    this Update lt Contact gt  context  context Entry modifiedContact   c   gt  c Active  c   gt  c ContactTypeId      Doku-so provided a cool approach using generic s  I used the concept to solve my issue but you just can t use  Doku-so s solution as is and in both this post and the linked post no one answered the usage error questions

User · Answer

I m late to the game here  but this is how I am doing it  I spent a while hunting for a solution I was satisified with  this produces an UPDATE statement ONLY for the fields that are changed  as you explicitly define what they are through a  white list  concept which is more secure to prevent web form injection anyway   An excerpt from my ISession data repository   public bool Update lt T gt  T item  params string   changedPropertyNames  where T      class  new          context Set lt T gt    Attach item       foreach  var propertyName in changedPropertyNames                   If we can t find the property  this line wil throw an exception             which is good as we want to know about it          context Entry item  Property propertyName  IsModified   true            return true      This could be wrapped in a try  catch if you so wished  but I personally like my caller to know about the exceptions in this scenario   It would be called in something like this fashion  for me  this was via an ASP NET Web API    if   session Update franchiseViewModel Franchise  new                Name          StartDate          throw new HttpResponseException new HttpResponseMessage HttpStatusCode NotFound

User · Answer

In Entity Framework Core  Attach returns the entry  so all you need is   var user   new User   Id   userId  Password   password    db Users Attach user  Property x   gt  x Password  IsModified   true  db SaveChanges

User · Answer

In EntityFramework Core 2 x there is no need for Attach       get a tracked entity  var entity   context User Find userId    entity someProp   someValue      other property changes might come here  context SaveChanges      Tried this in SQL Server and profiling it   exec sp executesql N SET NOCOUNT ON  UPDATE  User  SET  someProp     p0 WHERE  UserId     p1  SELECT   ROWCOUNT     N  p1 int  p0 bit   p1 1223424  p0 1   Find ensures that already loaded entities do not trigger a SELECT and also automatically attaches the entity if needed  from the docs                Finds an entity with the given primary key values  If an entity with the given primary key values             is being tracked by the context  then it is returned immediately without making a request to the             database  Otherwise  a query is made to the database for an entity with the given primary key values             and this entity  if found  is attached to the context and returned  If no entity is found  then             null is returned

[sql] How to update only one field using Entity Framework?

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