Question

This code is from one class

 Button pagebtn = new Button();
 pagebtn.Text = "2";

 pagebtn.Click += 
        listTopicPerPage_Click(this, new btnEventArgs() { btnNumber = 2 });

I get an underline on the eventHandler method saying..

cannot immplicitly convert type ‘void’
to ‘System.EventHandler’.

Why is that?

Code from a different class that i created:

class btnEventArgs : EventArgs
{
    public int btnNumber { get; set; }
}

Answer 1

To specify the event parameters you should create a event field in your class, and rise it up on demand:

public partial class WebForm1 : System.Web.UI.Page
{
    public event EventHandler<btnEventArgs> SampleEvent;

    public void DemoEvent(int val)
    {
        // Copy to a temporary variable to be thread-safe.
        EventHandler<btnEventArgs> temp = SampleEvent;
        if (temp != null)
            temp(this, new btnEventArgs { btnNumber = val });
    }


    protected void Page_Load(object sender, EventArgs e)
    {
        Button1.Click += new EventHandler(Button1_Click);
    }

    void Button1_Click(object sender, EventArgs e)
    {
        DemoEvent(2);
    }
}

class btnEventArgs : EventArgs 
{
    public int btnNumber { get; set; } 
}

MSDN article