Contract.OldValue(Of T) Method
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Represents values as they were at the start of a method or property.
Assembly: mscorlib (in mscorlib.dll)
The following example shows the use of the OldValue(Of T) method to ensure that a count has been updated. This code example is part of a larger example provided for the ContractClassAttribute class.
Sub Insert(ByVal index As Integer, ByVal value As [Object]) Implements IArray.Insert Contract.Requires(index >= 0) Contract.Requires(index <= CType(Me, IArray).Count) ' For inserting immediately after the end. Contract.Ensures(CType(Me, IArray).Count = Contract.OldValue(CType(Me, IArray).Count) + 1) End Sub 'IArray.Insert
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