Contract.OldValue<T> Method

This method can be used only in the conditional expression for the Ensures contract.

The following example shows the use of the OldValue<T> method to ensure that a count has been updated. This code example is part of a larger example provided for the ContractClassAttribute class.

void IArray.Insert(int index, Object value)
{
    Contract.Requires(index >= 0);
    Contract.Requires(index <= ((IArray)this).Count);  // For inserting immediately after the end.
    Contract.Ensures(((IArray)this).Count == Contract.OldValue(((IArray)this).Count) + 1);
}

.NET Framework

.NET Framework Client Profile

Portable Class Library

.NET for Windows Store apps

Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Reference