OnClick vs OnClientClick for an asp:CheckBox?

Question

Does anyone know why a client-side javascript handler for asp:CheckBox needs to be an OnClick=\"\" attribute rather than an OnClientClick=\"\" attribute, as for asp:Button?<

Answer 1

That is very weird. I checked the CheckBox documentation page which reads

As you can see, there is no OnClick or OnClientClick attributes defined.

Keeping this in mind, I think this is what is happening.

When you do this,

ASP.NET doesn't modify the OnClick attribute and renders it as is on the browser. It would be rendered as:

Obviously, a browser can understand 'OnClick' and puts an alert.

And in this scenario

Again, ASP.NET won't change the OnClientClick attribute and will render it as

As browser won't understand OnClientClick nothing will happen. It also won't raise any error as it is just another attribute.

You can confirm above by looking at the rendered HTML.

And yes, this is not intuitive at all.