Listening event outside MainPage class calling method multiple times on button click event (repetetively)

Question

I have a situation where I have to manage the button click event outside MainPage class (suppose in Class B). Here is the code that I'm using:

 namespace TEST
 {
     public partial class MainPage: UserControl 
     {
         public event Action simpleEvent;
         public MainPage() 
         {     
         }

         private void comboBox1_SelectionChanged(object sender, SelectionChangedEventArgs e)
         {
             switch (comboBox1.SelectedItem as string) 
             {
             case "UInt8":
                 B obj4 = new B(this, fileContent, "UInt8");
                 break;
             case "UInt16":
                 B obj1 = new B(this, fileContent, "UInt16");
                 break;
             case "UInt32":
                 B obj2 = new B(this, fileContent, "UInt32");
                 break;
             case "UInt64":
                 B obj3 = new B(this, fileContent, "UInt64");
                 goto
             default;
             default:
                 MessageBox.Show("check");
                 break;
             }
         }
         private void ButtonClick_EVENT(object sender, RoutedEventArgs e) 
         {
             // I try to listen outside the class this way.
             if (simpleEvent != null)
                 simpleEvent();
         }
     }

     Class B 
     {
         public B(MainPage Obj, byte[] fileContent, string type)
         {
             switch (type = Obj.comboBox1.SelectedItem as string)
             {
             case "UInt8":
                 {
                     //do something 
                     break;
                 }
             case "UInt16":
                 {
                     //do something
                     break;
                 }
             case "UInt32":
                 {
                     //do something 
                     break;
                 }

             case "UInt64":
                 {
                     //do something 
                     goto
                     default;
                 }
             default:
                 {
                     break;
                 }


             }
             Obj.simpleEvent += () = > MyMethod(Obj);
         }

         public void MyMethod(MainPage Obj) 
         {
             // This MessageBox repeats 2 times on second time button click
             // and 3 times on 3rd button click .
             // It should be called once even on second/third/fourth etc. button clicks.
             MessageBox.Show("Repetition check");
         }
     }
 }

The problem is my method is called repetitively. For example, when I click the button the first time it will be called only once (which is good). and if I click the button again the message box pop-up comes up 2 times and again pop-ups 3 times on 3rd attempt.

What I want is to pop-up this message box only once on the click (even if I keep on clicking on the button one after the other click).

EDIT: The new updated code is the actual situation i was trying to make it short so last time i didn't include to much code (because i was not suspecting that part).

What i am trying to do is : I have to select 1 data type among 4 given data type at run time (uint64/32/16/8)(which will be data type for reading a file ("fileContent" in constructor call), but it's not related to question i asked, so leaving too much discussion on it).After selecting that data type i click the button to display something. (so each time i first i select "data type" from combo box and then i press button to display some data corresponding to that data type then i again select another data type from combo box and then again i press "button" but this time it pop-ups message 2 times, and when i repeat the same 3rd time it pop-ups messagebox 3times).

Suppose first i selected "uint64" in combo box at run time (in the first attempt) and then i click button to display messagebox it will pop-up the message box once.Now without closing the application my second selection to combo box is on uint32 (On second attempt) and again i click to "button" this time this message box is popped 2 times. I don't know why? and on third attempt it pop-ups 3 times.

(1) Why message box repeats ? Thanks for the help in advance, I really wanna know the reason for it, not able to understand yet.

Answer 1

You're creating a new B object every time your combobox is changed. That adds a new handler every single time, without ever removing the previous handlers. You need to either unsubscribe the old handler when you go to add a new one, or only ever add one handler and simply modify the data that it relies on so that that handler acts appropriately when it fires.