Validating Time in ASP.NET using a Regular Expression

In one of the forums, I came across a question where a user wanted to validate time in ASP.NET. The requirements were the following:

- Acceptable values were 23:59, 00:00, 23 (equivalent to 23:00) and so on

- Values to be disallowed were 24:00, 23:5, 23:0 and so on

Here’s the regex shared by RQuadlin to achieve this requirement.

^([ 01]?[0-9]2[0-3])(:([0-5][0-9]))?$

In an ASP.NET scenario, we will be using a Regular Expression Validator to validate time. The markup will look similar to the following:

<div>
    <asp:TextBox ID="txtTime" runat="server">
    </asp:TextBox>       
    <asp:RegularExpressionValidator ID="rev"
    runat="server" ErrorMessage="InvalidTime" ControlToValidate="txtTime"
     ValidationExpression="^([ 01]?[0-9]2[0-3])(:([0-5][0-9]))?$">
    </asp:RegularExpressionValidator>
</div>