Editare

Partajați prin

Queryable.Contains Method

  • Reference

Definition

Namespace:
System.Linq
Assembly:
System.Linq.Queryable.dll
Assembly:
System.Core.dll
Assembly:
netstandard.dll

Determines whether an IQueryable<T> contains a specified element.

Overloads

Contains<TSource>(IQueryable<TSource>, TSource)

Determines whether a sequence contains a specified element by using the default equality comparer.
Contains<TSource>(IQueryable<TSource>, TSource, IEqualityComparer<TSource>)

Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.

Contains<TSource>(IQueryable<TSource>, TSource)

Source:
Queryable.cs
Source:
Queryable.cs
Source:
Queryable.cs

Determines whether a sequence contains a specified element by using the default equality comparer.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static bool Contains(System::Linq::IQueryable<TSource> ^ source, TSource item);
public static bool Contains<TSource> (this System.Linq.IQueryable<TSource> source, TSource item);
static member Contains : System.Linq.IQueryable<'Source> * 'Source -> bool
<Extension()>
Public Function Contains(Of TSource) (source As IQueryable(Of TSource), item As TSource) As Boolean

Type Parameters

TSource

The type of the elements of source.

Parameters

source
IQueryable<TSource>

An IQueryable<T> in which to locate item.

item
TSource

The object to locate in the sequence.

Returns

Boolean

true if the input sequence contains an element that has the specified value; otherwise, false.

Exceptions

ArgumentNullException

source is null.

Examples

The following code example demonstrates how to use Contains<TSource>(IQueryable<TSource>, TSource) to determine whether a sequence contains a specific element.

string[] fruits = { "apple", "banana", "mango",
                    "orange", "passionfruit", "grape" };

// The string to search for in the array.
string mango = "mango";

bool hasMango = fruits.AsQueryable().Contains(mango);

Console.WriteLine(
    "The array {0} contain '{1}'.",
    hasMango ? "does" : "does not",
    mango);

// This code produces the following output:
//
// The array does contain 'mango'.

Dim fruits() As String = {"apple", "banana", "mango", _
                        "orange", "passionfruit", "grape"}

' The string to search for in the array.
Dim mango As String = "mango"

Dim hasMango As Boolean = fruits.AsQueryable().Contains(mango)

MsgBox(String.Format("The array {0} contain '{1}'.", _
        IIf(hasMango, "does", "does not"), mango))

' This code produces the following output:
'
' The array does contain 'mango'.

Remarks

The Contains<TSource>(IQueryable<TSource>, TSource) method generates a MethodCallExpression that represents calling Contains<TSource>(IQueryable<TSource>, TSource) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Contains<TSource>(IQueryable<TSource>, TSource) depends on the implementation of the type of the source parameter. The expected behavior is that it determines if source contains item.

Applies to

Contains<TSource>(IQueryable<TSource>, TSource, IEqualityComparer<TSource>)

Source:
Queryable.cs
Source:
Queryable.cs
Source:
Queryable.cs

Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static bool Contains(System::Linq::IQueryable<TSource> ^ source, TSource item, System::Collections::Generic::IEqualityComparer<TSource> ^ comparer);
public static bool Contains<TSource> (this System.Linq.IQueryable<TSource> source, TSource item, System.Collections.Generic.IEqualityComparer<TSource> comparer);
public static bool Contains<TSource> (this System.Linq.IQueryable<TSource> source, TSource item, System.Collections.Generic.IEqualityComparer<TSource>? comparer);
static member Contains : System.Linq.IQueryable<'Source> * 'Source * System.Collections.Generic.IEqualityComparer<'Source> -> bool
<Extension()>
Public Function Contains(Of TSource) (source As IQueryable(Of TSource), item As TSource, comparer As IEqualityComparer(Of TSource)) As Boolean

Type Parameters

TSource

The type of the elements of source.

Parameters

source
IQueryable<TSource>

An IQueryable<T> in which to locate item.

item
TSource

The object to locate in the sequence.

comparer
IEqualityComparer<TSource>

An IEqualityComparer<T> to compare values.

Returns

Boolean

true if the input sequence contains an element that has the specified value; otherwise, false.

Exceptions

ArgumentNullException

source is null.

Remarks

The Contains<TSource>(IQueryable<TSource>, TSource, IEqualityComparer<TSource>) method generates a MethodCallExpression that represents calling Contains<TSource>(IQueryable<TSource>, TSource, IEqualityComparer<TSource>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Contains<TSource>(IQueryable<TSource>, TSource, IEqualityComparer<TSource>) depends on the implementation of the type of the source parameter. The expected behavior is that it determines if source contains item by using comparer to compare values.

Applies to