How do I make buttons do the same thing?

Question

I just started programming, and I want to use WinForms to make multiple buttons that you can click on to change from white to lime-green and back to white. I have done this for one button:

private void button1_Click(object sender, EventArgs e)
    {
        if (button1.BackColor != Color.Lime)
        {
            button1.BackColor = Color.Lime;
        }
        else
        {
            button1.BackColor = Color.White;
        }
    }

Now I could copy and paste that for all of the buttons, but I know that is inefficient; and if I use winforms to reference button1 on button2, it will just change the color of button1 (obviously).

So, do I need to use a helper method, new class, or something else? What would that look like?

Answer 1

There are a couple of approaches. One might be to create a common function which the different buttons call:

private void button1_Click(object sender, EventArgs e)
{
    ChangeColor(button1);
}

private void ChangeColor(Button button)
{
    if (button.BackColor != Color.Lime)
        button.BackColor = Color.Lime;
    else
        button.BackColor = Color.White;
}

Then each button handler can use that same function call.

Or, if all of these buttons will always ever do exactly the same thing, then you can use one click handler function for all of them. In this case what you'd need to do is determine which button invoked the handler (whereas you're currently referencing button1 directly) so that you know which one to change. The sender object passed into the handler function is actually a reference to the form element which invoked the handler. All you need to do is cast it:

private void button_Click(object sender, EventArgs e)
{
    var button = (Button)sender;
    if (button.BackColor != Color.Lime)
        button.BackColor = Color.Lime;
    else
        button.BackColor = Color.White;
}

So first the handler grabs a reference to the button which invoked it, then runs the logic on that button. Note also how I made the name of the handler function slightly more generic. Now you'd go to the form designer and set button_Click as the click handler for all of the buttons which should invoke this.

Answer 2

You do this the exact same way you'd do it for any C# class. You derive your own class and customize the base class behavior. Every event has a corresponding OnXxxx() method that you can override.

Add a new class to your project and paste this code:

using System;
using System.Windows.Forms;

class MyButton : Button {
    protected override void OnClick(EventArgs e) {
        // Your code here
        //...
        base.OnClick(e);
    }
}

Change the code in OnClick() to do what you want to do. Compile. You'll now have your own button control on the top of the toolbox. And can drop as many copies of it as you want on a form. They'll all behave the same without having to add any code in the form.