Question

I am validating a zip code using Javascript that is generated server-side, and injected when a LinkButton is clicked. Then, I retrieve the return value by calling a server-side function when the page loads.

This works nicely, but the problem is that the ViewState is completely lost after PostBack. Below is the code, starting with the page_load event, the button click event, and then the callback called from the page_load event.

Is there a way I can somehow save the ViewState, maybe easily in a session variable? Or is there a workaround I can use?

// In Page_Load if (Request.Form['__EVENTTARGET'] == 'CallFunction') {     GetValidateZipCodeScriptReturnValue(Boolean.Parse(Request.Form['__EVENTARGUMENT'].ToString())); }  // OnClick for LinkButton private bool ValidateZipCode(string zip) {     StringBuilder script = new StringBuilder();     script.Append('<script language='javascript' type='text/javascript'>');     script.Append(@'var regex = /^\d{5}$|^\d{5}-\d{4}$/;');     script.Append('__doPostBack('CallFunction', regex.test(' + zip + '));');     script.Append('</script>');      Type t = GetType();      if (!ClientScript.IsClientScriptBlockRegistered(t, 'ValidateZipCodeScript')) {         ClientScript.RegisterClientScriptBlock(t, 'ValidateZipCodeScript', script.ToString());     }      return false; }  // Method called on PostBack to get the return value of the javascript private void GetValidateZipCodeScriptReturnValue(bool valid) {     m_ZipCode = uxZip.Text;      if (valid) {         Response.Redirect(string.Format('~/checkout/overview.aspx?pc={0}&zc={1}',         ProductCode, ZipCode));     }     else {         Alert.Show('The entered zip code is invalid. Please ensure the zip code is a valid zip code.');         SetupPostBackViewState();         ScrollToZipCode();     } } 

Answer 1

Why not just use the OnClick event of the LinkButton? Or, better yet, look into the CustomValidator control, since it looks like all you’re trying to do is validate a zip code and that’s exactly what a CustomValidator can do (you’ll need to look at the ClientValidationFunction, which is where you want to put your regex test).