Contract.Requires Method (Boolean, String)

Specifies a precondition contract for the enclosing method or property, and displays a message if the condition for the contract fails.

Namespace:  System.Diagnostics.Contracts
Assembly:  mscorlib (in mscorlib.dll)


<ConditionalAttribute("CONTRACTS_FULL")> _
Public Shared Sub Requires ( _
    condition As Boolean, _
    userMessage As String _
public static void Requires(
    bool condition,
    string userMessage


  • userMessage
    Type: System.String
    The message to display if the condition is false.


  • This method call must be at the beginning of a method or property, before any other code.

  • This contract is exposed to clients; therefore, it must only reference members that are at least as visible as the enclosing method.

  • Use this method instead of the Contract.Requires<TException>(Boolean, String) method when backward compatibility does not force you to throw a particular exception.

Version Information


Supported in: 5, 4


For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.