Throughout the product development cycle, occasionally certain methods become obsolete. If you can't modify those methods, will need to write another implementation of the method using a slightly different name or signature. To maintain compatibility, you do not want to remove the old method and break your code. This is where the .NET Obsolete attribute comes in handy:
[Obsolete("Use the new LogRequestEx instead.")]
public static void LogRequest(string feedUrl, string referer)
{
...
Setting the Obsolete attribute as above makes a warning message appear in the Visual Studio's Error List stating that the particular call to a method is obsolete. The warning message also includes your personalized message that you pass as the attribute's argument (such as, "Use the new LogRequestEx instead").