C# Where to put general methods?

Question

In my application I have a method to check a variable is a number or not. This method is called more than once in my code. The method is called from the codebehind pages. Like this method I have more methods which i cannot place within a single class (like Staff). Where should I put this kind of methods?

Answer 1

In a utility class file.

Answer 2

In C# 3.0, I would probably make this an extension method on the string class. I would group all of my string extensions into a single static class to improve readability.

 public static class StringExtensions
 {
      public static bool IsNumeric( this string source )
      {
          if (string.IsNullOrEmpty( source ))
          { 
               return false;
          }
          ...
      }

      public static bool IsMoney( this string source )
      {
          ...
      }

      ...
 }

Usage:

 if (amountLabel.Text.IsNumeric())
 {
    ...
 }