How do I use a delegate on a button click

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On a button click, I want to call a delegate function.

it shows an error

Cannot assign to 'AddButtonClickDelegateCl' because it is a 'method group'

is this how delegate use?

on the button click, I want to execute a method on another class.

What I have tried:

class A

public void btn_click(string name)
        {
            AddButtonClickDelegateCl(name);
        }

    public delegate void OrderButtonClick(string name);
    public event OrderButtonClick AddButtonClickDelegateCl;

class B

     AddButtonClickDelegateCl+= AddButtonClick;

AddButtonClick()
{
//messagebox.show("success")
}

Posted 20-Dec-20 22:32pm

john321a

Updated 21-Dec-20 2:10am

v3

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Maciej Los 21-Dec-20 4:55am

And... What's wrong with your code? What' your issue?

3 solutions

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FranzBe · Answer 1 · 2020-12-20T23:09:00

your question is not clear to me, perhaps this might help

public interface IView1
{
    event EventHandler DoStuffOnButton1Click;
    void ShowMessage(string message);
}

public partial class Form1 : Form, IView1
{
    public event EventHandler DoStuffOnButton1Click;

    public Form1()
    {
        InitializeComponent();
        button1.Click += OnButton1Click;
        var presenter = new Form1Presenter(this);
    }

    public void ShowMessage(string message)
    {
        MessageBox.Show(message);
    }

    private void OnButton1Click(object sender, EventArgs e)
    {
        var handler = this.DoStuffOnButton1Click;
        handler?.Invoke(this, EventArgs.Empty);
    }

}


public class Form1Presenter
{
    IView1 _view;
    public Form1Presenter(IView1 view)
    {
        _view = view;
        WireUpEvents();
    }

    private void WireUpEvents()
    {
        _view.DoStuffOnButton1Click += OnDoStuff;
    }

    private void OnDoStuff(object sender, EventArgs e)
    {
        _view.ShowMessage("Button1 was clicked");
    }
}

OriginalGriff · Answer 2 · 2020-12-20T23:18:00

Solution 2

This may help: A Simple Code Snippet to Add an Event[^]

Posted 20-Dec-20 23:18pm

OriginalGriff

BillWoodruff · Answer 3 · 2020-12-21T02:10:00

For you to add a delegate instance to ClassA from ClassB requires the instance of ClassB to have a reference to an instance of ClassA.

And, the signatures (parameters) must march.

A typical example:

public FormA AInstance;
public FormB BInstance;

private void MainForm_Load(object sender, EventArgs e)
{
    AInstance = new FormA();
    BInstance = new FormB();
}

public  class FormA: Form
{
    public Action<string> OnButtonClick;

    private void btn_click(object sender, EventArgs e)
    {
        if  (OnButtonClick != null) OnButtonClick("some text");
    }
}

public class FormB: Form
{
    public void SetClassAClickHandler(FormA ainstance)
    {
        ainstance.OnButtonClick += OnButtonClick;
    }

    private void OnButtonClick(string text)
    {
        // do something
    }
}

Npte: the use of 'Action in ClassA is a recent C# language alternative syntax for writing a delegate that takes arguments, but does not return a value: [^]

How do I use a delegate on a button click

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