Uses of Action delegate in C# [closed]

Answer 1

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<String> 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.

Answer 2

For an example of how Action<> is used.

Console.WriteLine has a signature that satisifies Action<string>.

    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

Answer 3

I used the action delegate like this in a project once:

private static Dictionary<Type, Action<Control>> controldefaults = new Dictionary<Type, Action<Control>>() { 
            {typeof(TextBox), c => ((TextBox)c).Clear()},
            {typeof(CheckBox), c => ((CheckBox)c).Checked = false},
            {typeof(ListBox), c => ((ListBox)c).Items.Clear()},
            {typeof(RadioButton), c => ((RadioButton)c).Checked = false},
            {typeof(GroupBox), c => ((GroupBox)c).Controls.ClearControls()},
            {typeof(Panel), c => ((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.