# SortedSet<T>.IsProperSubsetOf(IEnumerable<T>)SortedSet<T>.IsProperSubsetOf(IEnumerable<T>)SortedSet<T>.IsProperSubsetOf(IEnumerable<T>)SortedSet<T>.IsProperSubsetOf(IEnumerable<T>) Method

## Definition

Determines whether a SortedSet<T> object is a proper subset of the specified collection.

``````public:
virtual bool IsProperSubsetOf(System::Collections::Generic::IEnumerable<T> ^ other);``````
``public bool IsProperSubsetOf (System.Collections.Generic.IEnumerable<T> other);``
``````abstract member IsProperSubsetOf : seq<'T> -> bool
override this.IsProperSubsetOf : seq<'T> -> bool``````
``Public Function IsProperSubsetOf (other As IEnumerable(Of T)) As Boolean``

#### Parameters

other
IEnumerable<T> IEnumerable<T> IEnumerable<T> IEnumerable<T>

The collection to compare to the current SortedSet<T> object.

#### Returns

`true` if the SortedSet<T> object is a proper subset of `other`; otherwise, `false`.

#### Exceptions

`other` is `null`.

## Remarks

An empty set is a proper subset of any other collection. Therefore, this method returns `true` if the collection represented by the current SortedSet<T> object is empty unless the `other` parameter is also an empty set.

This method always returns `false` if Count is greater than or equal to the number of elements in `other`.

If the collection represented by `other` is a SortedSet<T> collection with the same equality comparer as the current SortedSet<T> object, then this method is an `O(n)` operation. Otherwise, this method is an `O(n + m)` operation, where `n` is Count and `m` is the number of elements in `other`.