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LINQ to Objects

Aggregation

Aggregate, Average, Count, LongCount, Max, Min, Sum

      Aggregate (simple)       Aggregate (seed)       Average       Count       LongCount       Max       Min       Sum

Conversion

AsEnumerable, Cast, OfType, ToArray, ToDictionary, ToList, ToLookup

      AsEnumerable       Cast       OfType       ToArray       ToDictionary (simple)       ToDictionary (conditional)       ToList       ToLookup

Element

ElementAt, ElementAtOrDefault, First, FirstOrDefault, Last, LastOrDefault, Single, SingleOrDefault

      ElementAt       ElementAtOrDefault       First (simple)       First (conditional)       FirstOrDefault       Last       LastOrDefault (simple)       LastOrDefault (conditional)       Single       SingleOrDefault

Generation

DefaultIfEmpty, Empty, Range, Repeat

      DefaultIfEmpty (simple)       DefaultIfEmpty (default value)       Empty       Range       Repeat

Grouping

GroupBy

      GroupBy

Join

GroupJoin, Join

      GroupJoin (left outer join)       Join (inner join)

Ordering

OrderBy, OrderByDescending, Reverse, ThenBy, ThenByDescending

      OrderBy (simple - numbers)       OrderBy (simple - dates)       OrderBy (simple - objects)       OrderByDescending       Reverse       ThenBy       ThenByDescending

Other

Concat, SequenceEqual, Zip

      Concat (simple - numbers)       Concat (simple - strings)       SequenceEqual       Zip

Partitioning

Skip, SkipWhile, Take, TakeWhile

      Skip       SkipWhile       Take       TakeWhile

Projection

Select, SelectMany

      Select (simple)       Select (anonymous type)       Select (indexed)       SelectMany (cross join)

Quantifiers

All, Any, Contains

      All       Any       Contains

Restriction

Where

      Where (simple - numbers)       Where (simple - objects)       Where (indexed)

Set

Distinct, Except, Intersect, Union

      Distinct       Except       Intersect       Union
  Close

DefaultIfEmpty (default value)

Lambda Query

DefaultIfEmpty: If a collection is empty, its default value is returned. Default value depends on collection type. A default value may be specified.

DefaultIfEmpty: If a collection is empty, its default value is returned. Default value depends on collection type. A default value may be specified.

This Lambda Expression sample returns specified default value of 5 for empty array.

This Lambda Expression sample returns specified default value of 5 for empty array.

  • C#
  • VB.Net
  • F#
// A Query Expression cannot be constructed for DefaultIfEmpty() in C#.
// Consider using a Lambda Expression instead.
' A Query Expression cannot be constructed for DefaultIfEmpty() in VB.NET.
' Consider using a Lambda Expression instead.
// A Query Expression cannot be constructed for DefaultIfEmpty() in F#.
// Consider using a Lambda Expression instead.
  • C#
  • VB.Net
  • F#
static void Sample_DefaultIfEmpty_Lambda_DefaultValue()
{
    int[] empty = { };

    var result = empty.DefaultIfEmpty(5);

    Debug.WriteLine("result contains one element with a value of 5:");
    Debug.WriteLine(result.Count() == 1 && result.First() == 5);
}
Output:
result contains one element with a value of 5:
True
Private Shared Sub Sample_DefaultIfEmpty_Lambda_DefaultValue()
    Dim empty As Integer() = {}

    Dim result = empty.DefaultIfEmpty(5)

    Debug.WriteLine("result contains one element with a value of 5:")
    Debug.WriteLine(result.Count() = 1 AndAlso result.First() = 5)
End Sub
Output:
result contains one element with a value of 5:
True
let Sample_DefaultIfEmpty_Lambda_DefaultValue() =
    let empty = []

    let result = empty.DefaultIfEmpty(5)

    Debug.WriteLine(sprintf "result contains one element with a value of 5:")
    Debug.WriteLine(sprintf "%b" (result.Count() = 1 && result.First() = 5))
Output:
result contains one element with a value of 5:
true

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