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Enumerable.DefaultIfEmpty Method

.NET Framework 4

Returns the elements of an IEnumerable<T>, or a default valued singleton collection if the sequence is empty.

This member is overloaded. For complete information about this member, including syntax, usage, and examples, click a name in the overload list.

Overload List

	Name	Description
	DefaultIfEmpty<TSource>(IEnumerable<TSource>)	Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty.
	DefaultIfEmpty<TSource>(IEnumerable<TSource>, TSource)	Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty.

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Reference

Enumerable Class

System.Linq Namespace

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FAQ

Ordering

Note that DefaultIfEmpty applied to a sorted sequence will cause the sort order to be lost. This is because the ordered sequence is processed as a subquery later processed to finally implement the DefaultIfEmpty method. As SQL doesn't allow to sort a subquery, the ordering is ignored (or the generated SQL would be invalid).

History

7/20/2010
Patrice SCRIBE