How To validate Email ID a Form in ASP. Net.

<script language="javascript" type="text/javascript">
function validate()
{
if (document.getElementById("<%=TextBox1.ClientID%>").value=="")
      {
                 alert("Name can not be blank");
                 document.getElementById("<%=TextBox1.ClientID%>").focus();
                 return false;
      }
      
      if(document.getElementById("<%=TextBox2.ClientID %>").value=="")
      {
                 alert("Email id can not be blank");
                document.getElementById("<%=TextBox2.ClientID %>").focus();
                return false;
      }
     var emailPat= /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
     var emailid=document.getElementById("<%=TextBox2.ClientID %>").value;
     var matchArray = emailid.match(emailPat);
     if (matchArray == null)
    {
               alert("Your email address seems incorrect. Please try again.");
               document.getElementById("<%=TextBox2.ClientID %>").focus();
               return false;
    }
    if (document.getElementById("<%=TextBox3.ClientID%>").value=="")
      {
                 alert("Contact Number can not be blank");
                 document.getElementById("<%=TextBox3.ClientID%>").focus();
                 return false;
      }
     var digits="0123456789";
     var temp;
     for (var i=0;i<document.getElementById("<%=TextBox3.ClientID %>").value.length;i++)
     {
     temp=document.getElementById("<%=TextBox3.ClientID%>").value.substring(i,i+1);
     if (digits.indexOf(temp)==-1)
      {
      alert("Please enter correct Contact Number");
      document.getElementById("<%=TextBox3.ClientID%>").focus();
      return false;
      }
     }
      if(document.getElementById("<%=TextBox5.ClientID %>").value=="")
    {
      alert("City can not be blank");
     document.getElementById("<%=TextBox5.ClientID %>").value;
      document.getElementById("<%=TextBox5.ClientID %>").focus();
      return false;
    }
      if(document.getElementById("<%=TextBox6.ClientID %>").value=="")
    {
     alert("Password can not be blank");
     document.getElementById("<%=TextBox6.ClientID %>").value;
     document.getElementById("<%=TextBox6.ClientID %>").focus();
      return false;
    }
    if(document.getElementById("<%=TextBox7.ClientID %>").value=="")
    {
     alert("Please Re-Enter Password ");
   document.getElementById("<%=TextBox7.ClientID %>").value;
   document.getElementById("<%=TextBox7.ClientID %>").focus();
    return false;
    }
     return true;
}
</script>