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.
Assemblies: mscorlib (in mscorlib.dll)
System.Diagnostics.Contracts (in System.Diagnostics.Contracts.dll)
'Declaration <ConditionalAttribute("CONTRACTS_FULL")> _ Public Shared Sub Requires ( _ condition As Boolean, _ userMessage As String _ )
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(Of TException)(Boolean, String) method when backward compatibility does not force you to throw a particular exception.