Validate multiple valid emails separated by semicolon

Validate multiple valid emails separated by semicolon
There are various ways to validate them
1. Using custom validator and calling the javascript

 <asp:CustomValidator ID="custValEmail" runat="server" ClientValidationFunction="validateMultipleEmailsCommaSeparated"  ErrorMessage="Invalid email(s)"></asp:CustomValidator>

 <script language="JavaScript" type="text/javascript">

 function validateEmail(field)
 {
     var regex=/^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
     var matchArray=field.match(regex);
     if(matchArray==null)
         return false;
     else
         return true;
 }

 function validateMultipleEmailsCommaSeparated(source, value)
 {
     var result = document.getElementById("<%= txtEmail.ClientID %>").value.split(';');
     for(var i = 0;i < result.length;i++)
     {
         if(!validateEmail(result[i]))
         {
             value.IsValid = false;
             return false;
         }    
     }       
     value.IsValid = true;
 }
 </script>
 
2. Directly defining the regular expression in the RegularExpressionValidator control   
   
    <asp:RegularExpressionValidator ID="s" runat="server" ControlToValidate="txtEmail" ErrorMessage="Invalid email(s)" 
ValidationExpression="(([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)(\s*;\s*|\s*$))*"></asp:RegularExpressionValidator>