How to correctly understand sender in ASP. NET?

How to correctly understand sender in ASP. NET?

For example:

<Input type = "Submit" id = "A1" value = "Flash" onserverclick = "submit_click" runat = "server">

<Input type = "Submit" id = "A2" value = "bright" onserverclick = "submit_click" runat = "server">

<Input type = "Submit" id = "A3" value = "" onserverclick = "submit_click" runat = "server">

<Input type = "Submit" id = "A4" value = "sub" onserverclick =" submit_click "runat =" server ">

These are the four submit buttons. We know that the events triggered by this button are the same, but how can we differentiate them? Let's take a look at the following:

Public void submit_click (Object sender, eventargs E)

{

Switch (Control) sender). Id)

{

Case "A1": showmsg. Text = "" song yanhao; break;

Case "A2": showmsg. Text = "" Li yingbing; break;

Case "A3": showmsg. Text = "" Fei Wenhua; break;

Case "A4": showmsg. Text = "" Wu Xiaotao; break;

}

}

</SCRIPT>

<Asp: Label id = showmsg runat = server/>