public virtual bool IsExistingUser(
	IUserContext userContext,
	string userName
)

Public Overridable Function IsExistingUser ( 
	userContext As IUserContext,
	userName As String
) As Boolean

public:
virtual bool IsExistingUser(
	IUserContext^ userContext, 
	String^ userName
)

abstract IsExistingUser : 
        userContext : IUserContext * 
        userName : string -> bool 
override IsExistingUser : 
        userContext : IUserContext * 
        userName : string -> bool