Uses of Action delegate in C

Question

I was working with the Action Delegates in C  in the hope of learning more about them and thinking where they might be useful   Has anybody used the Action Delegate  and if so why  or could you give some examples where it might be useful

User · Accepted Answer

MSDN says      This delegate is used by the   Array ForEach method and the   List ForEach method to perform an   action on each element of the array or   list    Except that  you can use it as a generic delegate that takes 1-3 parameters without returning any value

User · Answer

I used it as a callback in an event handler  When I raise the event  I pass in a method taking a string a parameter  This is what the raising of the event looks like   SpecialRequest this      new BalieEventArgs                     Message    A Message                Action   UpdateMethod               Data   someDataObject            The Method      public void UpdateMethod string SpecialCode       The is the class declaration of the event Args   public class MyEventArgs   EventArgs               public string Message          public object Data          public Action lt String gt  Action          This way I can call the method passed from the event handler with a some parameter to update the data  I use this to request some information from the user

User · Answer

You can use actions for short event handlers   btnSubmit Click     sender  e    gt  MessageBox Show  You clicked save

User · Answer

I used the action delegate like this in a project once   private static Dictionary lt Type  Action lt Control gt  gt  controldefaults   new Dictionary lt Type  Action lt Control gt  gt                    typeof TextBox   c   gt    TextBox c  Clear                  typeof CheckBox   c   gt    CheckBox c  Checked   false                typeof ListBox   c   gt    ListBox c  Items Clear                  typeof RadioButton   c   gt    RadioButton c  Checked   false                typeof GroupBox   c   gt    GroupBox c  Controls ClearControls                  typeof Panel   c   gt    Panel c  Controls ClearControls             which all it does is store a action method call  against a type of control so that you can clear all the controls on a form back to there defaults

User · Answer

You can use actions for short event handlers   btnSubmit Click     sender  e    gt  MessageBox Show  You clicked save

User · Answer

I used it as a callback in an event handler  When I raise the event  I pass in a method taking a string a parameter  This is what the raising of the event looks like   SpecialRequest this      new BalieEventArgs                     Message    A Message                Action   UpdateMethod               Data   someDataObject            The Method      public void UpdateMethod string SpecialCode       The is the class declaration of the event Args   public class MyEventArgs   EventArgs               public string Message          public object Data          public Action lt String gt  Action          This way I can call the method passed from the event handler with a some parameter to update the data  I use this to request some information from the user

User · Answer

Well one thing you could do is if you have a switch   switch SomeEnum      case SomeEnum One        DoThings someUser         break    case SomeEnum Two        DoSomethingElse someUser         break      And with the might power of actions you can turn that switch into a dictionary   Dictionary lt SomeEnum  Action lt User gt  gt  methodList        new Dictionary lt SomeEnum  Action lt User gt  gt     methodList Add SomeEnum One  DoSomething   methodList Add SomeEnum Two  DoSomethingElse           methodList SomeEnum  someUser     Or you could take this farther   SomeOtherMethod Action lt User gt  someMethodToUse  User someUser        someMethodToUse someUser               var neededMethod   methodList SomeEnum   SomeOtherMethod neededMethod  someUser     Just a couple of examples   Of course the more obvious use would be Linq extension methods

User · Answer

Here is a small example that shows the usefulness of the Action delegate  using System  using System Collections Generic   class Program       static void Main                 Action lt String gt  print   new Action lt String gt  Program Print            List lt String gt  names   new List lt String gt     andrew    nicole              names ForEach print            Console Read               static void Print String s                Console WriteLine s             Notice that the foreach method iterates the collection of names and executes the print method against each member of the collection   This a bit of a paradigm shift for us C  developers as we move towards a more functional style of programming    For more info on the computer science behind it read this  http   en wikipedia org wiki Map  higher-order function    Now if you are using C  3 you can slick this up a bit with a lambda expression like so   using System  using System Collections Generic   class Program       static void Main                 List lt String gt  names   new List lt String gt     andrew    nicole              names ForEach s   gt  Console WriteLine s             Console Read

User · Answer

I used it as a callback in an event handler  When I raise the event  I pass in a method taking a string a parameter  This is what the raising of the event looks like   SpecialRequest this      new BalieEventArgs                     Message    A Message                Action   UpdateMethod               Data   someDataObject            The Method      public void UpdateMethod string SpecialCode       The is the class declaration of the event Args   public class MyEventArgs   EventArgs               public string Message          public object Data          public Action lt String gt  Action          This way I can call the method passed from the event handler with a some parameter to update the data  I use this to request some information from the user

User · Answer

For an example of how Action lt   is used   Console WriteLine has a signature that satisifies Action lt string gt        static void Main string   args                string   words    This is as easy as it looks  Split                   Passing WriteLine as the action         Array ForEach words  Console WriteLine                    Hope this helps

User · Answer

Here is a small example that shows the usefulness of the Action delegate  using System  using System Collections Generic   class Program       static void Main                 Action lt String gt  print   new Action lt String gt  Program Print            List lt String gt  names   new List lt String gt     andrew    nicole              names ForEach print            Console Read               static void Print String s                Console WriteLine s             Notice that the foreach method iterates the collection of names and executes the print method against each member of the collection   This a bit of a paradigm shift for us C  developers as we move towards a more functional style of programming    For more info on the computer science behind it read this  http   en wikipedia org wiki Map  higher-order function    Now if you are using C  3 you can slick this up a bit with a lambda expression like so   using System  using System Collections Generic   class Program       static void Main                 List lt String gt  names   new List lt String gt     andrew    nicole              names ForEach s   gt  Console WriteLine s             Console Read

User · Answer

For an example of how Action lt   is used   Console WriteLine has a signature that satisifies Action lt string gt        static void Main string   args                string   words    This is as easy as it looks  Split                   Passing WriteLine as the action         Array ForEach words  Console WriteLine                    Hope this helps

User · Answer

I use it when I am dealing with Illegal Cross Thread Calls For example   DataRow dr   GetRow    this Invoke new Action      gt       txtFname Text   dr  Fname   ToString       txtLname Text   dr  Lname   ToString        txtMI Text   dr  MI   ToString       txtSSN Text   dr  SSN   ToString       txtSSN ButtonsRight  OpenDialog   Visible   true     txtSSN ButtonsRight  ListSSN   Visible   true     txtSSN Focus           I must give credit to Reed Copsey SO user 65358 for the solution  My full question with answers is SO Question 2587930

User · Answer

Here is a small example that shows the usefulness of the Action delegate  using System  using System Collections Generic   class Program       static void Main                 Action lt String gt  print   new Action lt String gt  Program Print            List lt String gt  names   new List lt String gt     andrew    nicole              names ForEach print            Console Read               static void Print String s                Console WriteLine s             Notice that the foreach method iterates the collection of names and executes the print method against each member of the collection   This a bit of a paradigm shift for us C  developers as we move towards a more functional style of programming    For more info on the computer science behind it read this  http   en wikipedia org wiki Map  higher-order function    Now if you are using C  3 you can slick this up a bit with a lambda expression like so   using System  using System Collections Generic   class Program       static void Main                 List lt String gt  names   new List lt String gt     andrew    nicole              names ForEach s   gt  Console WriteLine s             Console Read

User · Answer

Well one thing you could do is if you have a switch   switch SomeEnum      case SomeEnum One        DoThings someUser         break    case SomeEnum Two        DoSomethingElse someUser         break      And with the might power of actions you can turn that switch into a dictionary   Dictionary lt SomeEnum  Action lt User gt  gt  methodList        new Dictionary lt SomeEnum  Action lt User gt  gt     methodList Add SomeEnum One  DoSomething   methodList Add SomeEnum Two  DoSomethingElse           methodList SomeEnum  someUser     Or you could take this farther   SomeOtherMethod Action lt User gt  someMethodToUse  User someUser        someMethodToUse someUser               var neededMethod   methodList SomeEnum   SomeOtherMethod neededMethod  someUser     Just a couple of examples   Of course the more obvious use would be Linq extension methods

User · Answer

I used it as a callback in an event handler  When I raise the event  I pass in a method taking a string a parameter  This is what the raising of the event looks like   SpecialRequest this      new BalieEventArgs                     Message    A Message                Action   UpdateMethod               Data   someDataObject            The Method      public void UpdateMethod string SpecialCode       The is the class declaration of the event Args   public class MyEventArgs   EventArgs               public string Message          public object Data          public Action lt String gt  Action          This way I can call the method passed from the event handler with a some parameter to update the data  I use this to request some information from the user

User · Answer

We use a lot of Action delegate functionality in tests  When we need to build some default object and later need to modify it  I made little example  To build default person  John Doe  object we use BuildPerson   function  Later we add Jane Doe too  but we modify her birthdate and name and height   public class Program           public static void Main string   args                        var person1   BuildPerson                 Console WriteLine person1 Firstname               Console WriteLine person1 Lastname               Console WriteLine person1 BirthDate               Console WriteLine person1 Height                var person2   BuildPerson p   gt                                p Firstname    Jane                   p BirthDate   DateTime Today                  p Height   1 76                               Console WriteLine person2 Firstname               Console WriteLine person2 Lastname               Console WriteLine person2 BirthDate               Console WriteLine person2 Height                Console Read                       public static Person BuildPerson Action lt Person gt  overrideAction   null                        var person   new Person                                 Firstname    John                   Lastname    Doe                   BirthDate   new DateTime 2012  2  2                              if  overrideAction    null                  overrideAction person                return person                       public class Person               public string Firstname   get  set            public string Lastname   get  set            public DateTime BirthDate   get  set            public double Height   get  set

User · Answer

I used the action delegate like this in a project once   private static Dictionary lt Type  Action lt Control gt  gt  controldefaults   new Dictionary lt Type  Action lt Control gt  gt                    typeof TextBox   c   gt    TextBox c  Clear                  typeof CheckBox   c   gt    CheckBox c  Checked   false                typeof ListBox   c   gt    ListBox c  Items Clear                  typeof RadioButton   c   gt    RadioButton c  Checked   false                typeof GroupBox   c   gt    GroupBox c  Controls ClearControls                  typeof Panel   c   gt    Panel c  Controls ClearControls             which all it does is store a action method call  against a type of control so that you can clear all the controls on a form back to there defaults

User · Answer

Well one thing you could do is if you have a switch   switch SomeEnum      case SomeEnum One        DoThings someUser         break    case SomeEnum Two        DoSomethingElse someUser         break      And with the might power of actions you can turn that switch into a dictionary   Dictionary lt SomeEnum  Action lt User gt  gt  methodList        new Dictionary lt SomeEnum  Action lt User gt  gt     methodList Add SomeEnum One  DoSomething   methodList Add SomeEnum Two  DoSomethingElse           methodList SomeEnum  someUser     Or you could take this farther   SomeOtherMethod Action lt User gt  someMethodToUse  User someUser        someMethodToUse someUser               var neededMethod   methodList SomeEnum   SomeOtherMethod neededMethod  someUser     Just a couple of examples   Of course the more obvious use would be Linq extension methods

User · Answer

I used the action delegate like this in a project once   private static Dictionary lt Type  Action lt Control gt  gt  controldefaults   new Dictionary lt Type  Action lt Control gt  gt                    typeof TextBox   c   gt    TextBox c  Clear                  typeof CheckBox   c   gt    CheckBox c  Checked   false                typeof ListBox   c   gt    ListBox c  Items Clear                  typeof RadioButton   c   gt    RadioButton c  Checked   false                typeof GroupBox   c   gt    GroupBox c  Controls ClearControls                  typeof Panel   c   gt    Panel c  Controls ClearControls             which all it does is store a action method call  against a type of control so that you can clear all the controls on a form back to there defaults

User · Answer

You can use actions for short event handlers   btnSubmit Click     sender  e    gt  MessageBox Show  You clicked save

User · Answer

For an example of how Action lt   is used   Console WriteLine has a signature that satisifies Action lt string gt        static void Main string   args                string   words    This is as easy as it looks  Split                   Passing WriteLine as the action         Array ForEach words  Console WriteLine                    Hope this helps

User · Answer

For an example of how Action lt   is used   Console WriteLine has a signature that satisifies Action lt string gt        static void Main string   args                string   words    This is as easy as it looks  Split                   Passing WriteLine as the action         Array ForEach words  Console WriteLine                    Hope this helps

User · Answer

I used the action delegate like this in a project once   private static Dictionary lt Type  Action lt Control gt  gt  controldefaults   new Dictionary lt Type  Action lt Control gt  gt                    typeof TextBox   c   gt    TextBox c  Clear                  typeof CheckBox   c   gt    CheckBox c  Checked   false                typeof ListBox   c   gt    ListBox c  Items Clear                  typeof RadioButton   c   gt    RadioButton c  Checked   false                typeof GroupBox   c   gt    GroupBox c  Controls ClearControls                  typeof Panel   c   gt    Panel c  Controls ClearControls             which all it does is store a action method call  against a type of control so that you can clear all the controls on a form back to there defaults

User · Answer

Here is a small example that shows the usefulness of the Action delegate  using System  using System Collections Generic   class Program       static void Main                 Action lt String gt  print   new Action lt String gt  Program Print            List lt String gt  names   new List lt String gt     andrew    nicole              names ForEach print            Console Read               static void Print String s                Console WriteLine s             Notice that the foreach method iterates the collection of names and executes the print method against each member of the collection   This a bit of a paradigm shift for us C  developers as we move towards a more functional style of programming    For more info on the computer science behind it read this  http   en wikipedia org wiki Map  higher-order function    Now if you are using C  3 you can slick this up a bit with a lambda expression like so   using System  using System Collections Generic   class Program       static void Main                 List lt String gt  names   new List lt String gt     andrew    nicole              names ForEach s   gt  Console WriteLine s             Console Read

User · Answer

I use it when I am dealing with Illegal Cross Thread Calls For example   DataRow dr   GetRow    this Invoke new Action      gt       txtFname Text   dr  Fname   ToString       txtLname Text   dr  Lname   ToString        txtMI Text   dr  MI   ToString       txtSSN Text   dr  SSN   ToString       txtSSN ButtonsRight  OpenDialog   Visible   true     txtSSN ButtonsRight  ListSSN   Visible   true     txtSSN Focus           I must give credit to Reed Copsey SO user 65358 for the solution  My full question with answers is SO Question 2587930

User · Answer

You can use actions for short event handlers   btnSubmit Click     sender  e    gt  MessageBox Show  You clicked save

User · Answer

Well one thing you could do is if you have a switch   switch SomeEnum      case SomeEnum One        DoThings someUser         break    case SomeEnum Two        DoSomethingElse someUser         break      And with the might power of actions you can turn that switch into a dictionary   Dictionary lt SomeEnum  Action lt User gt  gt  methodList        new Dictionary lt SomeEnum  Action lt User gt  gt     methodList Add SomeEnum One  DoSomething   methodList Add SomeEnum Two  DoSomethingElse           methodList SomeEnum  someUser     Or you could take this farther   SomeOtherMethod Action lt User gt  someMethodToUse  User someUser        someMethodToUse someUser               var neededMethod   methodList SomeEnum   SomeOtherMethod neededMethod  someUser     Just a couple of examples   Of course the more obvious use would be Linq extension methods

User · Answer

We use a lot of Action delegate functionality in tests  When we need to build some default object and later need to modify it  I made little example  To build default person  John Doe  object we use BuildPerson   function  Later we add Jane Doe too  but we modify her birthdate and name and height   public class Program           public static void Main string   args                        var person1   BuildPerson                 Console WriteLine person1 Firstname               Console WriteLine person1 Lastname               Console WriteLine person1 BirthDate               Console WriteLine person1 Height                var person2   BuildPerson p   gt                                p Firstname    Jane                   p BirthDate   DateTime Today                  p Height   1 76                               Console WriteLine person2 Firstname               Console WriteLine person2 Lastname               Console WriteLine person2 BirthDate               Console WriteLine person2 Height                Console Read                       public static Person BuildPerson Action lt Person gt  overrideAction   null                        var person   new Person                                 Firstname    John                   Lastname    Doe                   BirthDate   new DateTime 2012  2  2                              if  overrideAction    null                  overrideAction person                return person                       public class Person               public string Firstname   get  set            public string Lastname   get  set            public DateTime BirthDate   get  set            public double Height   get  set

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