Need to call java script method first, and then immediately after, call a C# method

I have an Asp.net web form. I need to validate my textbox controls on the client side, when a "Submit" button is pressed.
 
If the validation by my Java Script is correct, then I need to call a C# method. How can I do this? Is their a way to call my C# code after the Java script is executed? Would it be possible to have a hiddent button, and have my Java script press the hidden button, so that my server side code is executed?
 
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