calling a method from a string name

Question

I'm using c#, and I have a project that instantiates a lot of PictureBox buttons. I also have all of the click,hover,mouseUp,mouseDown event methods programmed. How do I call a method from a string name so that I don't have to write all of them by hand? Thanks in advance, Carson

Dictionary<string, PictureBox> buttonList = new Dictionary<string,PictureBox>();
string buttonName = "button_file";

buttonList[buttonName].Click += new EventHandler(buttonName + "_click");

public void button_file_click(object sender, EventArgs e)
{
     // do on click stuff here
}

Answer 1

if you set the Name property of button, you can so:

buttonList[buttonName].Name = buttonName;
buttonList[buttonName].Click += ButtonClick;

and only One metode hanle all buttons click but in accordance of their name:

public void ButtonClick(object sender, EventArgs e)
{
    var btn = (Button)sender;
    btn.Text = btn.Name;  //only for demo
}

but you can completely write your own method:

buttonList[buttonName].Click += (s,e)=> clickEvent(buttonList[buttonName], buttonName);

this is a short lambda function which accepts the parameters accordingly of Click event singature and fire your custom function, the clickEvent:

public void clickEvent(Button thePressedButton, string nameOfPresedButton)
{
    thePressedButton.Text = btn.nameOfPresedButton; //only for demo
}

Answer 2

From your sample code, I assume you want them all to call button_file_click.

In that case just set the eventhandler to that method:

buttonList[buttonName].Click += new EventHandler("button_file_click");

Answer 3

A method name isn't quite enough... you also need a class name... but assuming the method belongs to the current class (this) you can use Reflection to do this:

public void ExecuteMethod(string methodName)
{
    var methodInfo = this.GetType().GetMethod(methodName);
    methodInfo.Invoke(this, new [] {});
}

But you can't assign the above to an event because it is not the right delegate type; most event handlers require a sender and an EventArgs. So to make your code work you'd need a little more glue:

Dictionary<string, PictureBox> buttonList = new Dictionary<string,PictureBox>();
string buttonName = "button_file";

buttonList[buttonName].Click += GetHandler(buttonName + "_click");

public Action<object, EventArgs> GetHandler(string handlerName)
{
    var methodInfo = this.GetType().GetMethod(handlerName, new Type[] {typeof(object), typeof(EventArgs)});
    return new Action<object, EventArgs> (sender, eventArgs) => methodInfo.Invoke(this, new [] {sender, eventArgs});
}

The idea here is that GetHandler returns an Action with the right signature (accepting an object and an EventArgs, in that order), which is written as Action<object, EventArgs>. The GetHandler method uses reflection to find the right method in the current class, then creates a lambda expression that invokes the method via reflection, passing the arguments as an array.

The above is of course just an example... it would probably be better to store your delegates in a static dictionary that is computed when the page is loaded for the first time.

That being said, if you're looking for event handling flexibility based on a runtime parameter, a better approach is probably to use the Command event, which allows you to pass a string to the handler, which can then take a different action depending on the contents of the string. That way you can hardcode the handler reference but still softcode what it will do.

Dictionary<string, PictureBox> buttonList = new Dictionary<string,PictureBox>();
string buttonName = "button_file";

buttonList[buttonName].Command += buttonList_Command;
buttonList[buttonName].CommandName = buttonName;

protected void buttonList_Command(object sender, CommandEventArgs e)
{
     switch (e.CommandName)
     {
          case buttonName:
              //Do stuff for button_file
              break;
          case "Foo":
              //Do stuff for some other button named foo
              break;
          default:
              throw new InvalidOperationException();
     }
 }

Answer 4

You can use reflection to look up the method of a class by name and then create an event handler delegate using that method. For example:

 void bindHandler(string buttonName)
        {
            string methodName = buttonName + "_click";  
            System.Reflection.MethodInfo m = this.GetType().GetMethods().FirstOrDefault(x => x.Name == buttonName + "_click");
            PictureBox button = buttonList[buttonName];
            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), this, m);
            button.Click += (EventHandler)handler;
        }

Fulling working code:

namespace WindowsFormsApp1Cs
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            MyClass c = new MyClass();
            foreach (var item in c.buttonList)
            {
                this.Controls.Add(item.Value);
            }
        }
    }
    public class MyClass
    {
        public Dictionary<string, PictureBox> buttonList;
        public delegate void MyClickHandler(object sender, EventArgs e);
        public MyClass()
        {
            buttonList = new Dictionary<string, PictureBox>();
            buttonList.Add("button_file_1", new PictureBox() { Width = 100, Height = 100, Name = "button_file_1", Anchor = AnchorStyles.Top | AnchorStyles.Left, Top = (buttonList.Count * 100) + 10, Left = 10, ImageLocation="0.jpg" });
            buttonList.Add("button_file_2", new PictureBox() { Width = 100, Height = 100, Name = "button_file_2", Anchor = AnchorStyles.Top | AnchorStyles.Left, Top = (buttonList.Count * 100) + 10, Left = 10, ImageLocation = "0.jpg" });
            buttonList.Add("button_file_3", new PictureBox() { Width = 100, Height = 100, Name = "button_file_3", Anchor = AnchorStyles.Top | AnchorStyles.Left, Top = (buttonList.Count * 100) + 10, Left = 10, ImageLocation = "0.jpg" });
            foreach (var item in buttonList)
            {
                bindHandler(item.Key);
            }
        }
        void bindHandler(string buttonName)
        {
            string methodName = buttonName + "_click";  
            System.Reflection.MethodInfo m = this.GetType().GetMethods().FirstOrDefault(x => x.Name == buttonName + "_click");
            PictureBox button = buttonList[buttonName];
            Delegate handler = Delegate.CreateDelegate(typeof(EventHandler), this, m);
            button.Click += (EventHandler)handler;
        }
        public void button_file_1_click(object sender, EventArgs e)
        {
            Debug.WriteLine("button_file_1_click");
        }
        public void button_file_2_click(object sender, EventArgs e)
        {
            Debug.WriteLine("button_file_2_click");
        }
        public void button_file_3_click(object sender, EventArgs e)
        {
            Debug.WriteLine("button_file_3_click");
        }
    }
}