As i understand, there are possibilities to implement this code in C# instead of JavaScript to start manually uploading few files? I'm right?

P.S. I've met this expression first time: '<%=SubmitButton1.ClientID %>'?

P.S.S. What is this?  I cannot find any information about it.

P.S.S.S. Is there are any possibilities to use variable in this expression instead of number of button, for example?

Thanks,

Alexey