The server control cannot trigger the onclick event in HTML!

The problem that has plagued me for a long time is that the server control cannot write the oncick event of the button in HTML. It is actually quite simple in winter. Haha, because I am a beginner.

This is JS in HTML. I want to trigger it when I click the button, but the runat = "server" button prompts this error. After several twists and turns, I finally found a solution, haha. In the background file, that is, your XXX. CS
Private void page_load (Object sender, system. eventargs E)
{
// Place the user here CodeTo initialize the page
This. namecheck. Attributes. Add ("onclick", "Return checkinput ();");
}
Page_load. Add this. namecheck. Attributes. Add ("onclick", "Return checkinput ();");
This is OK, so that you can trigger checkinput () first (). It may be vague, but I think it should be understandable if someone encounters the same problem as me.
New handwriting is inevitable. Please teach me more!