DDL Item choice resetting when submitting form

Hello I have a DDL defined as:
<asp:DropDownList ID="trackerUsers" runat="server"></asp:DropDownList>
And an ASP Button defined as:
<asp:Button ID="reportBtn" Text="Run Report" runat="server" OnClick="selectedItemChanged" />
The Event Handler Function for the button is as follows:
public void selectedItemChanged(object sender, EventArgs e) { // Get the value of the currently selected item from the trackerUsers DDL String selectedUser = trackerUsers.SelectedValue.ToString(); // Parse the value of selectedUser to a function within the scope of the SQL namespace / class CAR.IDENTITY.user.getName(selectedUser); } Every time I debug and watch the value of selectedUser it always defaults to the first item in the list even when I specifically make an alternative choice.  I think it's something to do with post back or viewstate but I'm not sure.  Can anyone explain what the issu ...