Anonymous method in Invoke call

Question

Having a bit of trouble with the syntax where we want to call a delegate anonymously within a Control Invoke   We have tried a number of different approaches  all to no avail   For example   myControl Invoke delegate     MyMethod this  new MyEventArgs someParameter           where someParameter is local to this method  The above will result in a compiler error      Cannot convert anonymous method to type  System Delegate  because it is not a delegate type

User · Answer

Actually you do not need to use delegate keyword  Just pass lambda as parameter   control Invoke  MethodInvoker       gt   this Text    Hi

User · Answer

myControl Invoke new MethodInvoker delegate

User · Answer

Because Invoke BeginInvoke accepts Delegate  rather than a typed delegate   you need to tell the compiler what type of delegate to create   MethodInvoker  2 0  or Action  3 5  are common choices  note they have the same signature   like so   control Invoke  MethodInvoker  delegate  this Text    Hi        If you need to pass in parameters  then  captured variables  are the way   string message    Hi   control Invoke  MethodInvoker  delegate  this Text   message        caveat  you need to be a bit cautious if using captures async  but sync is fine - i e  the above is fine   Another option is to write an extension method   public static void Invoke this Control control  Action action        control Invoke  Delegate action       then   this Invoke delegate   this Text    hi          or since we are using C  3 0 this Invoke      gt    this Text    hi         You can of course do the same with BeginInvoke   public static void BeginInvoke this Control control  Action action        control BeginInvoke  Delegate action       If you can t use C  3 0  you could do the same with a regular instance method  presumably in a Form base-class

User · Answer

I like to use Action in place of MethodInvoker  it is shorter and looks cleaner   Invoke  Action       gt        DoSomething             OR  Invoke  Action delegate       DoSomething          Eg      Thread-safe update on a form control public void DisplayResult string text       if  txtResult InvokeRequired           txtResult Invoke  Action delegate               DisplayResult text                       return             txtResult Text    text     r n

User · Answer

For the sake of completeness  this can also be accomplished via an Action method anonymous method combination     Process is a method  invoked as a method group Dispatcher Current BeginInvoke  Action  Process     or use an anonymous method Dispatcher Current BeginInvoke  Action delegate   gt      SomeFunc      SomeOtherFunc

User · Answer

You need to create a delegate type  The keyword  delegate  in the anonymous method creation is a bit misleading  You are not creating an anonymous delegate but an anonymous method  The method you created can be used in a delegate  Like this   myControl Invoke new MethodInvoker delegate      MyMethod this  new MyEventArgs someParameter

User · Answer

myControl Invoke new MethodInvoker delegate

User · Answer

Actually you do not need to use delegate keyword  Just pass lambda as parameter   control Invoke  MethodInvoker       gt   this Text    Hi

User · Answer

myControl Invoke new MethodInvoker delegate

User · Answer

I never understood why this makes a difference for the compiler  but this is sufficient   public static class ControlExtensions       public static void Invoke this Control control  Action action                control Invoke action             Bonus  add some error handling  because it is likely that  if you are using Control Invoke from a background thread you are updating the text   progress   enabled state of a control and don t care if the control is already disposed   public static class ControlExtensions       public static void Invoke this Control control  Action action                try                       if   control IsDisposed  control Invoke action                     catch  ObjectDisposedException

User · Answer

You need to create a delegate type  The keyword  delegate  in the anonymous method creation is a bit misleading  You are not creating an anonymous delegate but an anonymous method  The method you created can be used in a delegate  Like this   myControl Invoke new MethodInvoker delegate      MyMethod this  new MyEventArgs someParameter

User · Answer

For the sake of completeness  this can also be accomplished via an Action method anonymous method combination     Process is a method  invoked as a method group Dispatcher Current BeginInvoke  Action  Process     or use an anonymous method Dispatcher Current BeginInvoke  Action delegate   gt      SomeFunc      SomeOtherFunc

User · Answer

Actually you do not need to use delegate keyword  Just pass lambda as parameter   control Invoke  MethodInvoker       gt   this Text    Hi

User · Answer

I had problems with the other suggestions because I want to sometimes return values from my methods  If you try to use MethodInvoker with return values it doesn t seem to like it  So the solution I use is like this  very happy to hear a way to make this more succinct - I m using c  net 2 0           Create delegates for the different return types needed      private delegate void VoidDelegate        private delegate Boolean ReturnBooleanDelegate        private delegate Hashtable ReturnHashtableDelegate            Now use the delegates and the delegate   keyword to create         an anonymous method as required         Here a case where there s no value returned      public void SetTitle string title                myWindow Invoke new VoidDelegate delegate                         myWindow Text   title                             Here s an example of a value being returned     public Hashtable CurrentlyLoadedDocs                 return  Hashtable myWindow Invoke new ReturnHashtableDelegate delegate                         return myWindow CurrentlyLoadedDocs

User · Answer

I like to use Action in place of MethodInvoker  it is shorter and looks cleaner   Invoke  Action       gt        DoSomething             OR  Invoke  Action delegate       DoSomething          Eg      Thread-safe update on a form control public void DisplayResult string text       if  txtResult InvokeRequired           txtResult Invoke  Action delegate               DisplayResult text                       return             txtResult Text    text     r n

User · Answer

I never understood why this makes a difference for the compiler  but this is sufficient   public static class ControlExtensions       public static void Invoke this Control control  Action action                control Invoke action             Bonus  add some error handling  because it is likely that  if you are using Control Invoke from a background thread you are updating the text   progress   enabled state of a control and don t care if the control is already disposed   public static class ControlExtensions       public static void Invoke this Control control  Action action                try                       if   control IsDisposed  control Invoke action                     catch  ObjectDisposedException

User · Answer

Because Invoke BeginInvoke accepts Delegate  rather than a typed delegate   you need to tell the compiler what type of delegate to create   MethodInvoker  2 0  or Action  3 5  are common choices  note they have the same signature   like so   control Invoke  MethodInvoker  delegate  this Text    Hi        If you need to pass in parameters  then  captured variables  are the way   string message    Hi   control Invoke  MethodInvoker  delegate  this Text   message        caveat  you need to be a bit cautious if using captures async  but sync is fine - i e  the above is fine   Another option is to write an extension method   public static void Invoke this Control control  Action action        control Invoke  Delegate action       then   this Invoke delegate   this Text    hi          or since we are using C  3 0 this Invoke      gt    this Text    hi         You can of course do the same with BeginInvoke   public static void BeginInvoke this Control control  Action action        control BeginInvoke  Delegate action       If you can t use C  3 0  you could do the same with a regular instance method  presumably in a Form base-class

User · Answer

Because Invoke BeginInvoke accepts Delegate  rather than a typed delegate   you need to tell the compiler what type of delegate to create   MethodInvoker  2 0  or Action  3 5  are common choices  note they have the same signature   like so   control Invoke  MethodInvoker  delegate  this Text    Hi        If you need to pass in parameters  then  captured variables  are the way   string message    Hi   control Invoke  MethodInvoker  delegate  this Text   message        caveat  you need to be a bit cautious if using captures async  but sync is fine - i e  the above is fine   Another option is to write an extension method   public static void Invoke this Control control  Action action        control Invoke  Delegate action       then   this Invoke delegate   this Text    hi          or since we are using C  3 0 this Invoke      gt    this Text    hi         You can of course do the same with BeginInvoke   public static void BeginInvoke this Control control  Action action        control BeginInvoke  Delegate action       If you can t use C  3 0  you could do the same with a regular instance method  presumably in a Form base-class

User · Answer

I had problems with the other suggestions because I want to sometimes return values from my methods  If you try to use MethodInvoker with return values it doesn t seem to like it  So the solution I use is like this  very happy to hear a way to make this more succinct - I m using c  net 2 0           Create delegates for the different return types needed      private delegate void VoidDelegate        private delegate Boolean ReturnBooleanDelegate        private delegate Hashtable ReturnHashtableDelegate            Now use the delegates and the delegate   keyword to create         an anonymous method as required         Here a case where there s no value returned      public void SetTitle string title                myWindow Invoke new VoidDelegate delegate                         myWindow Text   title                             Here s an example of a value being returned     public Hashtable CurrentlyLoadedDocs                 return  Hashtable myWindow Invoke new ReturnHashtableDelegate delegate                         return myWindow CurrentlyLoadedDocs

User · Answer

You need to create a delegate type  The keyword  delegate  in the anonymous method creation is a bit misleading  You are not creating an anonymous delegate but an anonymous method  The method you created can be used in a delegate  Like this   myControl Invoke new MethodInvoker delegate      MyMethod this  new MyEventArgs someParameter

User · Answer

You need to create a delegate type  The keyword  delegate  in the anonymous method creation is a bit misleading  You are not creating an anonymous delegate but an anonymous method  The method you created can be used in a delegate  Like this   myControl Invoke new MethodInvoker delegate      MyMethod this  new MyEventArgs someParameter

User · Answer

myControl Invoke new MethodInvoker delegate

User · Answer

I had problems with the other suggestions because I want to sometimes return values from my methods  If you try to use MethodInvoker with return values it doesn t seem to like it  So the solution I use is like this  very happy to hear a way to make this more succinct - I m using c  net 2 0           Create delegates for the different return types needed      private delegate void VoidDelegate        private delegate Boolean ReturnBooleanDelegate        private delegate Hashtable ReturnHashtableDelegate            Now use the delegates and the delegate   keyword to create         an anonymous method as required         Here a case where there s no value returned      public void SetTitle string title                myWindow Invoke new VoidDelegate delegate                         myWindow Text   title                             Here s an example of a value being returned     public Hashtable CurrentlyLoadedDocs                 return  Hashtable myWindow Invoke new ReturnHashtableDelegate delegate                         return myWindow CurrentlyLoadedDocs

User · Answer

I had problems with the other suggestions because I want to sometimes return values from my methods  If you try to use MethodInvoker with return values it doesn t seem to like it  So the solution I use is like this  very happy to hear a way to make this more succinct - I m using c  net 2 0           Create delegates for the different return types needed      private delegate void VoidDelegate        private delegate Boolean ReturnBooleanDelegate        private delegate Hashtable ReturnHashtableDelegate            Now use the delegates and the delegate   keyword to create         an anonymous method as required         Here a case where there s no value returned      public void SetTitle string title                myWindow Invoke new VoidDelegate delegate                         myWindow Text   title                             Here s an example of a value being returned     public Hashtable CurrentlyLoadedDocs                 return  Hashtable myWindow Invoke new ReturnHashtableDelegate delegate                         return myWindow CurrentlyLoadedDocs

User · Answer

Actually you do not need to use delegate keyword  Just pass lambda as parameter   control Invoke  MethodInvoker       gt   this Text    Hi

User · Answer

Because Invoke BeginInvoke accepts Delegate  rather than a typed delegate   you need to tell the compiler what type of delegate to create   MethodInvoker  2 0  or Action  3 5  are common choices  note they have the same signature   like so   control Invoke  MethodInvoker  delegate  this Text    Hi        If you need to pass in parameters  then  captured variables  are the way   string message    Hi   control Invoke  MethodInvoker  delegate  this Text   message        caveat  you need to be a bit cautious if using captures async  but sync is fine - i e  the above is fine   Another option is to write an extension method   public static void Invoke this Control control  Action action        control Invoke  Delegate action       then   this Invoke delegate   this Text    hi          or since we are using C  3 0 this Invoke      gt    this Text    hi         You can of course do the same with BeginInvoke   public static void BeginInvoke this Control control  Action action        control BeginInvoke  Delegate action       If you can t use C  3 0  you could do the same with a regular instance method  presumably in a Form base-class

[c#] Anonymous method in Invoke call

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