How to call function inside Repeater

Hi frnds,
Some time we need to edit our items inside repeater. for this condition we can call a function that is being called at item bind inside repeater. This function will be called on every item.

Lets go for one example.
Suppose we are getting Customer name with their mail ID but our requirement is to display only Name .

abc@gmail.com, xyz@gmail.com, dums@gmail.com

These are the customer information but we need to display only
abc,  xyz, dums

so in this condition we can call a function that will give our need , but important point where we will call that
function
So here is the solution

<asp:Label runat="server" id="lblUser" text='<%# userName(Eval("EmailID"))%>' ></asp:Label>

here i am calling one function that's name is "userName()" and passing value EmailID .
This function will return wat we need

Thanks
Shailendra