Make buttons in List send unique data to method

Question

I made a application which will place out buttons in a grid where the user specifies how big the playfield should be. I create the buttons in a list, specify some data like backgroundimage, size, and location. I then need to, in some way make the different buttons execute different code. I figured I could do this in one method, (if there aren't any good ways to programmatically create methods), if I could somehow make the buttons send a unique piece of information to the method to identify which button is pressed.

    public void buttonplacer()
    {
        int nbrofbtns = Form2.puzzlesize * Form2.puzzlesize;



        List<Button> btnslist = new List<Button>();
        for (int i = 0; i < nbrofbtns; i++)
        {

            Button newButton = new Button();
            btnslist.Add(newButton);
            this.Controls.Add(newButton);

            newButton.Name = "btn" + i.ToString();
            newButton.Width = btnsidelength;
            newButton.Height = btnsidelength;
            newButton.Top = btnsidelength * Convert.ToInt32(Math.Floor(Convert.ToDouble(i / Form2.puzzlesize)));
            newButton.Left = btnsidelength * Convert.ToInt32(Math.Floor(Convert.ToDouble(i)) - Math.Floor((Convert.ToDouble(i)) / (Form2.puzzlesize)) * (Form2.puzzlesize));
            newButton.BackgroundImage = Lights_out_.Properties.Resources.LightsOutBlack;




            newButton.Click += new EventHandler(Any_Button_Click);
        }
    }
    void Any_Button_Click(object sender, EventArgs e)
    {

    }

(If you want to know I'm doing a game called "Light's out") Thanks in advance!

Answer 1

The Any_Button_Click method receives an object sender that is the button that got clicked. You just need to cast it to a Button:

void Any_Button_Click(object sender, EventArgs e)
{
    Button b = (Button)sender;
    // do stuff here
}

You can use the button's Location property to figure out where it sits on the game board, or you can assign an arbitrary object to the button with any information you choose at initialization time using the Tag property like this:

button.Tag = "someHelpfulString";

or like this:

button.Tag = new Tuple<int, int>(xpos, ypos);

(where xpos and ypos are positions in the button grid)

or like this:

button.Tag = new ButtonInfoObject(foo, bar, baz);

(Here it's up to you to define the ButtonInfoObject class.)

Answer 2

As an alternative to other answers, and in particular to somewhat address the part "good ways to programmatically create methods", there is part of the C# language called Lambda Expressions. To keep long story short, you could write something along these lines:

newButton.Click += (s, e) =>
{
    //here you have access to all variables accessible in current scope,
    //including "newButton" and "i";
    //you could, for example, call some method passing "i" as an argument
    //or just put that method's code inside this block
};

The only downside of this approach is that you need to take some extra care if you're planning to unregister the handler at some later point (see this question or this question for reference).

EDIT

As pointed in comments I overlooked the fact that i stays in scope for the whole for loop, so using it inside lambda is pretty much pointless (all handlers will use it's final value). To make it behave like expected one can simply define a variable inside the loop so it goes out of scope at the end of each iteration and is stored separately for each handler:

var btnNo = i;
newButton.Click += (s, e) =>
{
    //use "btnNo" instead of "i"
    //you can still safely use "newButton" reference
    //since it's defined inside the loop
}

Answer 3

Use the sender object to get the button's name that was pressed:

void Any_Button_Click(object sender, EventArgs e)
{
     switch ((sender as Button).Name)
     {
         case "btn0":
             //...
             break;
         case "btn1":
             //...
             break;
         //...
     }
}