.NET/ASP.NET Interview Question - How to Validate a Controls in ASP.NET page using JavaScript?

Answer:
Let's see an Simple example to understand.

Assuming that we have a Textbox and Button on the ASP.NET page like
below.

<asp:TextBox ID="txtName" runat="server"></asp:TextBox>
<asp:Button ID="btnSubmit" runat="server" Text="Submit"
OnClientClick="return validate()" />

Now, Add the below code snippet on the page source.

<script language="javascript" type="text/javascript">
function ValidateTextBox()  
{
 if(document.getElementById("<%=txtName.ClientID%>").value == "")      
{             
 alert("Name Field Cannot be Empty");
 document.getElementById("<%=txtName.ClientID%>").focus();
  return false;    
 }
  return true;
}
</script>

Once you have completed the above steps, just run the project and see the result.
Regards,
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