Trying to validate a **comma-separated email list** in the textbox with `asp:RegularExpressionValidator`, see below:

```
<asp:RegularExpressionValidator ID="RegularExpressionValidator1"
                    runat="server" ErrorMessage="Wrong email format (separate multiple email by comma [,])" ControlToValidate="txtEscalationEmail"
                    Display="Dynamic" ValidationExpression="([\w+-.%]+@[\w-.]+\.[A-Za-z]{2,4},?)" ValidationGroup="vgEscalation"></asp:RegularExpressionValidator>

```

It works just fine when I test it at <http://regexhero.net/tester/>, but it doesn't work on my page.

Here's my sample input:

```
test@test.com,test1@test.com

```

I've tried a suggestion in [this post](https://stackoverflow.com/questions/1598349/problem-with-asp-net-custom-validator-for-a-comma-separated-list-of-email-address), but couldn't get it to work.

p.s. I don't want a discussion on proper email validation