Queryable Class
 
System_CAPS_noteNote

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Provides a set of static (Shared in Visual Basic) methods for querying data structures that implement IQueryable.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

SystemObject
  System.LinqQueryable

public static class Queryable
[ExtensionAttribute]
public ref class Queryable abstract sealed 
[<AbstractClass>]
[<Sealed>]
type Queryable = class end
<ExtensionAttribute>
Public NotInheritable Class Queryable
NameDescription
System_CAPS_pubmethod System_CAPS_static Aggregate

Applies an accumulator function over a sequence.

System_CAPS_pubmethod System_CAPS_static Aggregate

Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.

System_CAPS_pubmethod System_CAPS_static Aggregate

Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.

System_CAPS_pubmethod System_CAPS_static All

Determines whether all the elements of a sequence satisfy a condition.

System_CAPS_pubmethod System_CAPS_static Any

Determines whether a sequence contains any elements.

System_CAPS_pubmethod System_CAPS_static Any

Determines whether any element of a sequence satisfies a condition.

System_CAPS_pubmethod System_CAPS_static AsQueryable

Converts an IEnumerable to an IQueryable.

System_CAPS_pubmethod System_CAPS_static AsQueryable

Converts a generic IEnumerable to a generic IQueryable.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Decimal values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Double values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Int32 values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Int64 values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Decimal values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Double values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Int32 values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Int64 values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Single values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Single values.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Decimal values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Double values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Int32 values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Int64 values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Decimal values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Double values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Int32 values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Int64 values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of nullable Single values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Average

Computes the average of a sequence of Single values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Cast

Converts the elements of an IQueryable to the specified type.

System_CAPS_pubmethod System_CAPS_static Concat

Concatenates two sequences.

System_CAPS_pubmethod System_CAPS_static Contains

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

System_CAPS_pubmethod System_CAPS_static Contains

Determines whether a sequence contains a specified element by using a specified IEqualityComparer.

System_CAPS_pubmethod System_CAPS_static Count

Returns the number of elements in a sequence.

System_CAPS_pubmethod System_CAPS_static Count

Returns the number of elements in the specified sequence that satisfies a condition.

System_CAPS_pubmethod System_CAPS_static DefaultIfEmpty

Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty.

System_CAPS_pubmethod System_CAPS_static DefaultIfEmpty

Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty.

System_CAPS_pubmethod System_CAPS_static Distinct

Returns distinct elements from a sequence by using the default equality comparer to compare values.

System_CAPS_pubmethod System_CAPS_static Distinct

Returns distinct elements from a sequence by using a specified IEqualityComparer to compare values.

System_CAPS_pubmethod System_CAPS_static ElementAt

Returns the element at a specified index in a sequence.

System_CAPS_pubmethod System_CAPS_static ElementAtOrDefault

Returns the element at a specified index in a sequence or a default value if the index is out of range.

System_CAPS_pubmethod System_CAPS_static Except

Produces the set difference of two sequences by using the default equality comparer to compare values.

System_CAPS_pubmethod System_CAPS_static Except

Produces the set difference of two sequences by using the specified IEqualityComparer to compare values.

System_CAPS_pubmethod System_CAPS_static First

Returns the first element of a sequence.

System_CAPS_pubmethod System_CAPS_static First

Returns the first element of a sequence that satisfies a specified condition.

System_CAPS_pubmethod System_CAPS_static FirstOrDefault

Returns the first element of a sequence, or a default value if the sequence contains no elements.

System_CAPS_pubmethod System_CAPS_static FirstOrDefault

Returns the first element of a sequence that satisfies a specified condition or a default value if no such element is found.

System_CAPS_pubmethod System_CAPS_static GroupBy

Groups the elements of a sequence according to a specified key selector function.

System_CAPS_pubmethod System_CAPS_static GroupBy

Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.

System_CAPS_pubmethod System_CAPS_static GroupBy

Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.

System_CAPS_pubmethod System_CAPS_static GroupBy

Groups the elements of a sequence and projects the elements for each group by using a specified function. Key values are compared by using a specified comparer.

System_CAPS_pubmethod System_CAPS_static GroupBy

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.

System_CAPS_pubmethod System_CAPS_static GroupBy

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Keys are compared by using a specified comparer.

System_CAPS_pubmethod System_CAPS_static GroupBy

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function.

System_CAPS_pubmethod System_CAPS_static GroupBy

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Keys are compared by using a specified comparer and the elements of each group are projected by using a specified function.

System_CAPS_pubmethod System_CAPS_static GroupJoin

Correlates the elements of two sequences based on key equality and groups the results. The default equality comparer is used to compare keys.

System_CAPS_pubmethod System_CAPS_static GroupJoin

Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer is used to compare keys.

System_CAPS_pubmethod System_CAPS_static Intersect

Produces the set intersection of two sequences by using the default equality comparer to compare values.

System_CAPS_pubmethod System_CAPS_static Intersect

Produces the set intersection of two sequences by using the specified IEqualityComparer to compare values.

System_CAPS_pubmethod System_CAPS_static Join

Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys.

System_CAPS_pubmethod System_CAPS_static Join

Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer is used to compare keys.

System_CAPS_pubmethod System_CAPS_static Last

Returns the last element in a sequence.

System_CAPS_pubmethod System_CAPS_static Last

Returns the last element of a sequence that satisfies a specified condition.

System_CAPS_pubmethod System_CAPS_static LastOrDefault

Returns the last element in a sequence, or a default value if the sequence contains no elements.

System_CAPS_pubmethod System_CAPS_static LastOrDefault

Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.

System_CAPS_pubmethod System_CAPS_static LongCount

Returns an Int64 that represents the total number of elements in a sequence.

System_CAPS_pubmethod System_CAPS_static LongCount

Returns an Int64 that represents the number of elements in a sequence that satisfy a condition.

System_CAPS_pubmethod System_CAPS_static Max

Returns the maximum value in a generic IQueryable.

System_CAPS_pubmethod System_CAPS_static Max

Invokes a projection function on each element of a generic IQueryable and returns the maximum resulting value.

System_CAPS_pubmethod System_CAPS_static Min

Returns the minimum value of a generic IQueryable.

System_CAPS_pubmethod System_CAPS_static Min

Invokes a projection function on each element of a generic IQueryable and returns the minimum resulting value.

System_CAPS_pubmethod System_CAPS_static OfType

Filters the elements of an IQueryable based on a specified type.

System_CAPS_pubmethod System_CAPS_static OrderBy

Sorts the elements of a sequence in ascending order according to a key.

System_CAPS_pubmethod System_CAPS_static OrderBy

Sorts the elements of a sequence in ascending order by using a specified comparer.

System_CAPS_pubmethod System_CAPS_static OrderByDescending

Sorts the elements of a sequence in descending order according to a key.

System_CAPS_pubmethod System_CAPS_static OrderByDescending

Sorts the elements of a sequence in descending order by using a specified comparer.

System_CAPS_pubmethod System_CAPS_static Reverse

Inverts the order of the elements in a sequence.

System_CAPS_pubmethod System_CAPS_static Select

Projects each element of a sequence into a new form.

System_CAPS_pubmethod System_CAPS_static Select

Projects each element of a sequence into a new form by incorporating the element's index.

System_CAPS_pubmethod System_CAPS_static SelectMany

Projects each element of a sequence to an IEnumerable and combines the resulting sequences into one sequence.

System_CAPS_pubmethod System_CAPS_static SelectMany

Projects each element of a sequence to an IEnumerable and combines the resulting sequences into one sequence. The index of each source element is used in the projected form of that element.

System_CAPS_pubmethod System_CAPS_static SelectMany

Projects each element of a sequence to an IEnumerable and invokes a result selector function on each element therein. The resulting values from each intermediate sequence are combined into a single, one-dimensional sequence and returned.

System_CAPS_pubmethod System_CAPS_static SelectMany

Projects each element of a sequence to an IEnumerable that incorporates the index of the source element that produced it. A result selector function is invoked on each element of each intermediate sequence, and the resulting values are combined into a single, one-dimensional sequence and returned.

System_CAPS_pubmethod System_CAPS_static SequenceEqual

Determines whether two sequences are equal by using the default equality comparer to compare elements.

System_CAPS_pubmethod System_CAPS_static SequenceEqual

Determines whether two sequences are equal by using a specified IEqualityComparer to compare elements.

System_CAPS_pubmethod System_CAPS_static Single

Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.

System_CAPS_pubmethod System_CAPS_static Single

Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists.

System_CAPS_pubmethod System_CAPS_static SingleOrDefault

Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.

System_CAPS_pubmethod System_CAPS_static SingleOrDefault

Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.

System_CAPS_pubmethod System_CAPS_static Skip

Bypasses a specified number of elements in a sequence and then returns the remaining elements.

System_CAPS_pubmethod System_CAPS_static SkipWhile

Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.

System_CAPS_pubmethod System_CAPS_static SkipWhile

Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of Decimal values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of Double values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of Int32 values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of Int64 values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of nullable Decimal values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of nullable Double values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of nullable Int32 values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of nullable Int64 values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of nullable Single values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of a sequence of Single values.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of Decimal values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of Double values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of Int32 values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of Int64 values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of nullable Decimal values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of nullable Double values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of nullable Int32 values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of nullable Int64 values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of nullable Single values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Sum

Computes the sum of the sequence of Single values that is obtained by invoking a projection function on each element of the input sequence.

System_CAPS_pubmethod System_CAPS_static Take

Returns a specified number of contiguous elements from the start of a sequence.

System_CAPS_pubmethod System_CAPS_static TakeWhile

Returns elements from a sequence as long as a specified condition is true.

System_CAPS_pubmethod System_CAPS_static TakeWhile

Returns elements from a sequence as long as a specified condition is true. The element's index is used in the logic of the predicate function.

System_CAPS_pubmethod System_CAPS_static ThenBy

Performs a subsequent ordering of the elements in a sequence in ascending order according to a key.

System_CAPS_pubmethod System_CAPS_static ThenBy

Performs a subsequent ordering of the elements in a sequence in ascending order by using a specified comparer.

System_CAPS_pubmethod System_CAPS_static ThenByDescending

Performs a subsequent ordering of the elements in a sequence in descending order, according to a key.

System_CAPS_pubmethod System_CAPS_static ThenByDescending

Performs a subsequent ordering of the elements in a sequence in descending order by using a specified comparer.

System_CAPS_pubmethod System_CAPS_static Union

Produces the set union of two sequences by using the default equality comparer.

System_CAPS_pubmethod System_CAPS_static Union

Produces the set union of two sequences by using a specified IEqualityComparer.

System_CAPS_pubmethod System_CAPS_static Where

Filters a sequence of values based on a predicate.

System_CAPS_pubmethod System_CAPS_static Where

Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.

System_CAPS_pubmethod System_CAPS_static Zip

Merges two sequences by using the specified predicate function.

The set of methods declared in the Queryable class provides an implementation of the standard query operators for querying data sources that implement IQueryable. The standard query operators are general purpose methods that follow the LINQ pattern and enable you to express traversal, filter, and projection operations over data in any .NET-based programming language.

The majority of the methods in this class are defined as extension methods that extend the IQueryable type. This means they can be called like an instance method on any object that implements IQueryable. These methods that extend IQueryable do not perform any querying directly. Instead, their functionality is to build an Expression object, which is an expression tree that represents the cumulative query. The methods then pass the new expression tree to either the Execute method or the CreateQuery method of the input IQueryable. The method that is called depends on whether the Queryable method returns a singleton value, in which case Execute is called, or has enumerable results, in which case CreateQuery is called.

The actual query execution on the target data is performed by a class that implements IQueryable. The expectation of any IQueryable implementation is that the result of executing an expression tree that was constructed by a Queryable standard query operator method is equivalent to the result of calling the corresponding method in the Enumerable class, if the data source were an IEnumerable.

In addition to the standard query operator methods that operate on IQueryable objects, this class also contains a method, AsQueryable, which types IEnumerable objects as IQueryable objects.

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1

Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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