Enumerable.Count Method
Definition
Important
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Returns the number of elements in a sequence.
Overloads
Count<TSource>(IEnumerable<TSource>) |
Returns the number of elements in a sequence. |
Count<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) |
Returns a number that represents how many elements in the specified sequence satisfy a condition. |
Count<TSource>(IEnumerable<TSource>)
- Source:
- Count.cs
- Source:
- Count.cs
- Source:
- Count.cs
Returns the number of elements in a sequence.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static int Count(System::Collections::Generic::IEnumerable<TSource> ^ source);
public static int Count<TSource> (this System.Collections.Generic.IEnumerable<TSource> source);
static member Count : seq<'Source> -> int
<Extension()>
Public Function Count(Of TSource) (source As IEnumerable(Of TSource)) As Integer
Type Parameters
- TSource
The type of the elements of source
.
Parameters
- source
- IEnumerable<TSource>
A sequence that contains elements to be counted.
Returns
The number of elements in the input sequence.
Exceptions
source
is null
.
The number of elements in source
is larger than Int32.MaxValue.
Examples
The following code example demonstrates how to use Count<TSource>(IEnumerable<TSource>) to count the elements in an array.
string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };
try
{
int numberOfFruits = fruits.Count();
Console.WriteLine(
"There are {0} fruits in the collection.",
numberOfFruits);
}
catch (OverflowException)
{
Console.WriteLine("The count is too large to store as an Int32.");
Console.WriteLine("Try using the LongCount() method instead.");
}
// This code produces the following output:
//
// There are 6 fruits in the collection.
' Create an array of strings.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}
Try
' Count the number of items in the array.
Dim numberOfFruits As Integer = fruits.Count()
' Display the output.
Console.WriteLine($"There are {numberOfFruits} fruits in the collection.")
Catch e As OverflowException
Console.WriteLine("The count is too large to store as an Int32. Try using LongCount() instead.")
End Try
' This code produces the following output:
'
' There are 6 fruits in the collection.
Remarks
If the type of source
implements ICollection<T>, that implementation is used to obtain the count of elements. Otherwise, this method determines the count.
Use the LongCount method when you expect and want to allow the result to be greater than MaxValue.
In Visual Basic query expression syntax, an Aggregate Into Count()
clause translates to an invocation of Count.
See also
Applies to
Count<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
- Source:
- Count.cs
- Source:
- Count.cs
- Source:
- Count.cs
Returns a number that represents how many elements in the specified sequence satisfy a condition.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static int Count(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);
public static int Count<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);
static member Count : seq<'Source> * Func<'Source, bool> -> int
<Extension()>
Public Function Count(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean)) As Integer
Type Parameters
- TSource
The type of the elements of source
.
Parameters
- source
- IEnumerable<TSource>
A sequence that contains elements to be tested and counted.
Returns
A number that represents how many elements in the sequence satisfy the condition in the predicate function.
Exceptions
source
or predicate
is null
.
The number of elements in source
is larger than Int32.MaxValue.
Examples
The following code example demonstrates how to use Count<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) to count the elements in an array that satisfy a condition.
class Pet
{
public string Name { get; set; }
public bool Vaccinated { get; set; }
}
public static void CountEx2()
{
Pet[] pets = { new Pet { Name="Barley", Vaccinated=true },
new Pet { Name="Boots", Vaccinated=false },
new Pet { Name="Whiskers", Vaccinated=false } };
try
{
int numberUnvaccinated = pets.Count(p => p.Vaccinated == false);
Console.WriteLine("There are {0} unvaccinated animals.", numberUnvaccinated);
}
catch (OverflowException)
{
Console.WriteLine("The count is too large to store as an Int32.");
Console.WriteLine("Try using the LongCount() method instead.");
}
}
// This code produces the following output:
//
// There are 2 unvaccinated animals.
Structure Pet
Public Name As String
Public Vaccinated As Boolean
End Structure
Public Shared Sub CountEx2()
' Create an array of Pet objects.
Dim pets() As Pet = {New Pet With {.Name = "Barley", .Vaccinated = True},
New Pet With {.Name = "Boots", .Vaccinated = False},
New Pet With {.Name = "Whiskers", .Vaccinated = False}}
Try
' Count the number of Pets in the array where the Vaccinated property is False.
Dim numberUnvaccinated As Integer =
pets.Count(Function(p) p.Vaccinated = False)
' Display the output.
Console.WriteLine($"There are {numberUnvaccinated} unvaccinated animals.")
Catch e As OverflowException
Console.WriteLine("The count is too large to store as an Int32. Try using LongCount() instead.")
End Try
End Sub
' This code produces the following output:
'
' There are 2 unvaccinated animals.
Remarks
If the type of source
implements ICollection<T>, that implementation is used to obtain the count of elements. Otherwise, this method determines the count.
You should use the LongCount method when you expect and want to allow the result to be greater than MaxValue.
In Visual Basic query expression syntax, an Aggregate Into Count()
clause translates to an invocation of Count.