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ISet<T>.IsProperSubsetOf Method

Determines whether the current set is a proper (strict) subset of a specified collection.

Namespace:  System.Collections.Generic
Assembly:  System (in System.dll)

bool IsProperSubsetOf(
	IEnumerable<T> other


Type: System.Collections.Generic.IEnumerable<T>
The collection to compare to the current set.

Return Value

Type: System.Boolean
true if the current set is a proper subset of other; otherwise, false.


other is null.

If the current set is a proper subset of other, other must have at least one element that the current set does not have.

An empty set is a correct subset of any other collection. Therefore, this method returns true if the current set is empty, unless the other parameter is also an empty set.

This method always returns false if the current set has more or the same number of elements than other.

.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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