Reusing expression in asp.NET regex validation control

Question

I have this in an ascx file:

<asp:textbox ID="AddHourlyRate" runat="server" width="55px" />
<asp:RegularExpressionValidator  ID="AddHourlyRateRegexValidator"
    ErrorMessage="Please enter a valid charge rate (whole number only)" 
    ValidationExpression="^\$?[0-9]+(\.[0]{2})?$" ControlToValidate="AddHourlyRate" 
    Display="Dynamic" runat="server" />

How can I reuse the ValidationExpression in other asp:RegularExpressionValidators without having to copy-paste the regex expression? I am new to asp.NET.

Answer 1

Make a class with const string for each regular expression, I use that solution for your exact problem. That class is in a common assembly that is shared among number of projects. And you probably use regular expression on some other places not just validator controls.

Something like this :

public class RegularExpressions
{
  public const string TelephoneValidation = @"^[0-9 ]+$";
  public const string IntegerValidation = @"^\d+$";
}

You can then set validator expression from code behind :

validator.ValidationExpression = RegularExpressions.IntegerValidation;

or in markup :

<%@ Import Namespace="RegularExpression.Class.Namespace" %>  
.
.
.  
<asp:RegularExpressionValidator  ID="AddHourlyRateRegexValidator"
        ErrorMessage="Please enter a valid charge rate (whole number only)" 
        ValidationExpression="<%# RegularExpressions.IntegerValidation %>" ControlToValidate="AddHourlyRate" 
        Display="Dynamic" runat="server" />

Of course write proper namespace in import directive.