Update textbox through selected item in listbox

In ASP.NET I have a dropdown with some items in it, I have a button and a textbox. I am subscribed to the SelectedIndexChanged event of the dropdown where I pass the new selected index of the dropdown to a struct that converts it's index (via enum) to a string. That string is then gotten through a property in a class to put into the textbox.

//Enum and struct representing index to string conversion for dropdown

Public Enum e_action
    AcOne = 0
    AcTwo
    AcThree
    AcThree
  开发者_Go百科  AcFour

End Enum

Public Structure Action
    Public Sub New(ByVal index As Integer)
        Select Case index
            Case 0
                action = e_action.AcOne
            Case 1
                action = e_action.AcTwo
            Case 2
                action = e_action.AcThree
            Case 3
                action = e_action.AcFour
            Case 4
                action = e_action.AcFive
           End Select
    End Sub

// this is the selectedIndexChanged function for the dropdown

  Protected Sub dropdownAction_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles dropdownAction.SelectedIndexChanged
        Dim ddl As DropDownList = TryCast(sender, DropDownList)

        If Not IsNothing(ddl) Then
            Dim act As New Action(ddl.SelectedIndex)
            p_two_action = act  //p_two_action is a global var of type Action
        End If
    End Sub 


//inside the button handler

dim myclass as MyClass

MyTextBox.Text = myclass.getAction //returns string of action done in dropdown

Now the problem I have is that, when you click it (the button) the first time, the action get's updated with the current action selected in the listbox, but then when you click the button again WITHOUT changing anything in the listbox, the textbox shows the zero'th item in the textbox, (seems to reset), although it actually hasn't changed at all.

I'm guessing this might have something to do with the postback caused by the button click, which resets the state of the global or something, but I'm not sure. Why is it being reset while the dropdown box is still as I set it the first time?

Can someone help?

If this is not clear, please leave a comment on what is not clear. Thx!

The second time around (when you click the button but don't select anything in the list), the SelectedIndexChanged event wont get raised (since you didn't change the selected index).

You'll need to make sure that your logic in the button handler can also get the proper action for the current selected index of the drop down. The p_two_action seems to be getting reset - when you say it is a global how have you implemented it?