public WhoseValueConstraint<TCollection,TKey,TValue,TAssertions> ContainKey( 
   TKey expected,
   string because,
   params object[] becauseArgs
)

Parameters

expected

The expected key

because

A formatted phrase as is supported by System.String.Format(System.String,System.Object[]) explaining why the assertion is needed. If the phrase does not start with the word because, it is prepended automatically.

becauseArgs

Zero or more objects to format using the placeholders in because.

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

GenericDictionaryAssertions<TCollection,TKey,TValue,TAssertions> Class
GenericDictionaryAssertions<TCollection,TKey,TValue,TAssertions> Members