Question

This my asp:RegularExpressionValidator

  <asp:RegularExpressionValidator ID="RegularExpressionValidator2" 
                runat="server" ControlToValidate="uxTrachoCtrl1"
                ErrorMessage="Ne dois pas contenir des caractères alphabétiques"  
                ValidationExpression="[0123456789,.<>=]" ValidationGroup="verification" Display="Dynamic" 
                SetFocusOnError="True">
            </asp:RegularExpressionValidator>    

The string can contain only those characters 0123456789,.<>=

This my regex [0123456789,.<,>,=]

It works if I type one character like f or 1, but if I put more than one character this will raise an error:

ex: input="1"=ok
    input="f"=error
    input="11"=error (It's supposed to be right)

Answer 1

The character class matches only one character. You need to repeat it if you want to allow arbitrary length characters:

"[0-9,.<>=]*"

If you want to exclude empty inputs use this instead:

"[0-9,.<>=]+"

Note that my character class is equivalent to yours (0-9 is a shorthand notation for 0123456789 and you had the , multiple times in your character class).