MoreEnumerable.SingleOrFallback<TSource> Method |
Note: This API is now obsolete.
Returns the single element in the given sequence, or the result
of executing a fallback delegate if the sequence is empty.
This method throws an exception if there is more than one element in the sequence.
Namespace: MoreLinq
Assembly: MoreLinq (in MoreLinq.dll) Version: 2.5.0
Syntax[ObsoleteAttribute("Consider using FallbackIfEmpty instead. SingleOrFallback may be removed in a future version. For more information, see https://github.com/morelinq/MoreLINQ/issues/122.")] public static TSource SingleOrFallback<TSource>( this IEnumerable<TSource> source, Func<TSource> fallback )
Parameters
- source
- Type: System.Collections.Generic.IEnumerable<TSource>
The source sequence - fallback
- Type: System.Func<TSource>
The fallback delegate to execute if the sequence is empty
Type Parameters
- TSource
- Element type of sequence
Return Value
Type: TSourceThe single element in the sequence, or the result of calling the fallback delegate if the sequence is empty.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).Exceptions| Exception | Condition |
|---|---|
| ArgumentNullException | source or fallback is null |
| InvalidOperationException | The sequence has more than one element |
Remarks
The fallback delegate is not executed if the sequence is non-empty.
This operator uses immediate execution and has optimizations for IList< T> sources.
Examplesvar numbers = { 123, 456, 789 }; var result = numbers.Where(x => x == 100).SingleOrFallback(() => -1);
See Also