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Contract.OldValue(T) Method

Represents values as they were at the start of a method or property.

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

static member OldValue : 
        value:'T -> 'T 

Type Parameters

T

The type of value.

Parameters

value
Type: T

The value to represent (field or parameter).

Return Value

Type: T
The value of the parameter or field at the start of a method or property.

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.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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