Contract.Ensures Method (Boolean)


Specifies a postcondition contract for the enclosing method or property.

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

Public Shared Sub Ensures (
	condition As Boolean


Type: System.Boolean

The conditional expression to test. The expression may include OldValue(Of T), ValueAtReturn(Of T), and Result(Of T) values.

The condition parameter specifies a postcondition that is expected to be true when the enclosing method or property returns normally.

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

  • You must use the binary rewriter (available at Code Contracts on the MSDN DevLabs Web site) for run-time enforcement of this postcondition.

The following example shows how to use the Ensures method to ensure that an expected value is returned. This code example is part of a larger example provided for the ContractClassAttribute class.

Function Add(ByVal value As Object) As Integer Implements IArray.Add
    ' Returns the index in which an item was inserted.
    Contract.Ensures(Contract.Result(Of Integer)() >= -1) '
    Contract.Ensures(Contract.Result(Of Integer)() < CType(Me, IArray).Count) '
    Return 0

End Function 'IArray.Add

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Available since 4.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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