Queryable Class

Represents a query that can be executed against a data source. The Queryable class provides static methods that operate on an IQueryable object.

Methods

• Aggregate (IQueryable<TSource> source, Expression<Func<TSource, TAccumulate, TAccumulate>> func)
  Applies an accumulator function over a sequence.
• Aggregate (IQueryable<TSource> source, TAccumulate seed, Expression<Func<TAccumulate, TSource, TAccumulate>> func)
  Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.
• Aggregate (IQueryable<TSource> source, TAccumulate seed, Expression<Func<TAccumulate, TSource, TAccumulate>> func, Expression<Func<TAccumulate, TResult>> selector)
  Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified selector function is used to transform the final accumulator value.
• All (IQueryable<TSource> source, Expression<Func<TSource, bool>> predicate)
  Determines whether all elements of a sequence satisfy a condition.
• Any (IQueryable<TSource> source)
  Determines whether any element of a sequence exists.
• Any (IQueryable<TSource> source, Expression<Func<TSource, bool>> predicate)
  Determines whether any element of a sequence satisfies a condition.
• Average (IQueryable<int> source)
  Computes the average of a sequence of int values.
• Average (IQueryable<Nullable<int>> source)
  Computes the average of a sequence of nullable int values.
• Cast (IQueryable source)
  Casts the elements of a sequence to the specified type.
• Concat (IQueryable<TSource> source1, IQueryable<TSource> source2)
  Concatenates two sequences.
• Contains (IQueryable<TSource> source, TSource item)
  Determines whether a sequence contains a specified element.
• Count (IQueryable<TSource> source)
  Returns the number of elements in a sequence.
• Count (IQueryable<TSource> source, Expression<Func<TSource, bool>> predicate)
  Returns the number of elements in a sequence that satisfy a condition.
• DefaultIfEmpty (IQueryable<TSource> source)
  Returns the elements of the specified sequence or a default value in a singleton collection if the sequence is empty.
• DefaultIfEmpty (IQueryable<TSource> source, TSource defaultValue)
  Returns the elements of the specified sequence or a specified default value in a singleton collection if the sequence is empty.
• Distinct (IQueryable<TSource> source)
  Returns distinct elements from a sequence.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector)
  Groups the elements of a sequence according to a specified key selector function.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, IEqualityComparer<TKey> comparer)
  Groups the elements of a sequence according to a specified key selector function and key comparer.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector)
  Groups the elements of a sequence according to a specified key selector function.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector, IEqualityComparer<TKey> comparer)
  Groups the elements of a sequence according to a specified key selector function and key comparer.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TGroup>> groupSelector, Expression<Func<TKey, IEnumerable<TGroup>, TResult>> resultSelector)
  Groups the elements of a sequence according to a specified key selector function and creates a result value from each group.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector, Expression<Func<TKey, IEnumerable<TElement>> groupSelector)
  Groups the elements of a sequence according to a specified key selector function.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector, Expression<Func<TKey, IEnumerable<TElement>> groupSelector, IEqualityComparer<TKey> comparer)
  Groups the elements of a sequence according to a specified key selector function and key comparer.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TGroup>> groupSelector, Expression<Func<TKey, IEnumerable<TGroup>> resultSelector, IEqualityComparer<TKey> comparer)
  Groups the elements of a sequence according to a specified key selector function and key comparer, and creates a result value from each group.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector, Expression<Func<TKey, IEnumerable<TElement>, TResult>> resultSelector)
  Groups the elements of a sequence according to a specified key selector function and creates a result value from each group.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector, Expression<Func<TKey, IEnumerable<TElement>> groupSelector, Expression<Func<TKey, IEnumerable<TElement>, TResult>> resultSelector)
  Groups the elements of a sequence according to a specified key selector function and creates a result value from each group.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector, Expression<Func<TKey, IEnumerable<TElement>> groupSelector, Expression<Func<TKey, IEnumerable<TElement>> resultSelector, IEqualityComparer<TKey> comparer)
  Groups the elements of a sequence according to a specified key selector function and key comparer, and creates a result value from each group.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector, Expression<Func<TKey, IEnumerable<TElement>, TResult>> resultSelector, IEqualityComparer<TKey> comparer)
  Groups the elements of a sequence according to a specified key selector function and key comparer, and creates a result value from each group.
• GroupBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector, Expression<Func<TKey, IEnumerable<TElement>> groupSelector, Expression<Func<TKey, IEnumerable<TElement>> resultSelector, IEqualityComparer<TKey> comparer)
  Groups the elements of a sequence according to a specified key selector function and key comparer, and creates a result value from each group.
• GroupJoin (IQueryable<TOuter> outer, IQueryable<TInner> inner, Expression<Func<TOuter, TKey>> outerKeySelector, Expression<Func<TInner, TKey>> innerKeySelector, Expression<Func<TOuter, IEnumerable<TInner>, TResult>> resultSelector)
  Correlates the elements of two sequences based on matching keys and groups the results.
• GroupJoin (IQueryable<TOuter> outer, IQueryable<TInner> inner, Expression<Func<TOuter, TKey>> outerKeySelector, Expression<Func<TInner, TKey>> innerKeySelector, Expression<Func<TOuter, IEnumerable<TInner>, TResult>> resultSelector, IEqualityComparer<TKey> comparer)
  Correlates the elements of two sequences based on matching keys and groups the results.
• Join (IQueryable<TOuter> outer, IQueryable<TInner> inner, Expression<Func<TOuter, TKey>> outerKeySelector, Expression<Func<TInner, TKey>> innerKeySelector, Expression<Func<TOuter, TInner, TResult>> resultSelector)
  Correlates the elements of two sequences based on matching keys.
• Join (IQueryable<TOuter> outer, IQueryable<TInner> inner, Expression<Func<TOuter, TKey>> outerKeySelector, Expression<Func<TInner, TKey>> innerKeySelector, Expression<Func<TOuter, TInner, TResult>> resultSelector, IEqualityComparer<TKey> comparer)
  Correlates the elements of two sequences based on matching keys.
• Last (IQueryable<TSource> source)
  Returns the last element of a sequence.
• LastOrDefault (IQueryable<TSource> source)
  Returns the last element of a sequence, or a default value if the sequence is empty.
• LastOrDefault (IQueryable<TSource> source, TSource defaultValue)
  Returns the last element of a sequence, or a specified default value if the sequence is empty.
• Max (IQueryable<TSource> source)
  Returns the maximum value of a sequence.
• Max (IQueryable<TSource> source, Expression<Func<TSource, int>> selector)
  Returns the maximum value of a sequence of int values.
• Min (IQueryable<TSource> source)
  Returns the minimum value of a sequence.
• Min (IQueryable<TSource> source, Expression<Func<TSource, int>> selector)
  Returns the minimum value of a sequence of int values.
• OfType (IQueryable source)
  Filters the elements of an IEnumerable based on a specified type.
• OrderBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector)
  Sorts the elements of a sequence in ascending order.
• OrderBy (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, IComparer<TKey> comparer)
  Sorts the elements of a sequence in ascending order by using a specified comparer.
• OrderByDescending (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector)
  Sorts the elements of a sequence in descending order.
• OrderByDescending (IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, IComparer<TKey> comparer)
  Sorts the elements of a sequence in descending order by using a specified comparer.
• Range (int start, int count)
  Generates a sequence of integral numbers within a specified range.
• Repeat (TElement element, int count)
  Generates a sequence that contains one repeated value.
• Reverse (IQueryable<TSource> source)
  Reverses the order of the elements in a sequence.
• Select (IQueryable<TSource> source, Expression<Func<TSource, TResult>> selector)
  Projects each element of a sequence into a new form.
• SelectMany (IQueryable<TSource> source, Expression<Func<TSource, IEnumerable<TResult>>> selector)
  Projects each element of a sequence to an IEnumerable<TResult> and flattens the resulting sequences into one sequence.
• SelectMany (IQueryable<TSource> source, Expression<Func<TSource, TResult, TResult>> selector)
  Projects each element of a sequence to a new form by incorporating the element's index.
• SelectMany (IQueryable<TSource> source, Expression<Func<TSource, IEnumerable<TResult>>> selector, Expression<Func<TSource, IEnumerable<TResult>, TResult>> resultSelector)
  Projects each element of a sequence to an IEnumerable<TResult>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.
• SelectMany (IQueryable<TSource> source, Expression<Func<TSource, TResult, TResult>> selector, Expression<Func<TSource, TResult, TResult>> resultSelector)
  Projects each element of a sequence to a new form by incorporating the element's index.
• Single (IQueryable<TSource> source)
  Returns the only element of a sequence, and a default value if the sequence is empty; throws an exception if there is more than one element in the sequence.
• SingleOrDefault (IQueryable<TSource> source)
  Returns the only element of a sequence, or a default value if the sequence is empty; throws an exception if there is more than one element in the sequence.
• SingleOrDefault (IQueryable<TSource> source, TSource defaultValue)
  Returns the only element of a sequence, or a specified default value if the sequence is empty; throws an exception if there is more than one element in the sequence.
• Skip (IQueryable<TSource> source, int count)
  Bypasses a specified number of elements in a sequence and then returns the remaining elements.
• SkipWhile (IQueryable<TSource> source, Expression<Func<TSource, bool>> predicate)
  Bypasses elements in a sequence as long as a specified condition is met and then returns the remaining elements.
• SkipWhile (IQueryable<TSource> source, Expression<Func<TSource, int, bool>> predicate)
  Bypasses elements in a sequence as long as a specified condition is met and then returns the remaining elements. The element's index is used in the predicate's evaluation.
• Sum (IQueryable<int> source)
  Computes the sum of a sequence of int values.
• Sum (IQueryable<Nullable<int>> source)
  Computes the sum of a sequence of nullable int values.
• Take (IQueryable<TSource> source, int count)
  Returns a specified number of contiguous elements from the start of a sequence.
• TakeWhile (IQueryable<TSource> source, Expression<Func<TSource, bool>> predicate)
  Returns elements from a sequence as long as a specified condition is met.
• TakeWhile (IQueryable<TSource> source, Expression<Func<TSource, int, bool>> predicate)
  Returns elements from a sequence as long as a specified condition is met. The element's index is used in the predicate's evaluation.
• ThenBy (IOrderedQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector)
  Performs a subsequent ordering of the elements in a sequence in ascending order.
• ThenBy (IOrderedQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, IComparer<TKey> comparer)
  Performs a subsequent ordering of the elements in a sequence in ascending order by using a specified comparer.
• ThenByDescending (IOrderedQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector)
  Performs a subsequent ordering of the elements in a sequence in descending order.
• ThenByDescending (IOrderedQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, IComparer<TKey> comparer)
  Performs a subsequent ordering of the elements in a sequence in descending order by using a specified comparer.
• Union (IQueryable<TSource> source1, IQueryable<TSource> source2)
  Produces the set union of two sequences.
• Union (IQueryable<TSource> source1, IQueryable<TSource> source2, IEqualityComparer<TSource> comparer)
  Produces the set union of two sequences by using the specified equality comparer.
• Where (IQueryable<TSource> source, Expression<Func<TSource, bool>> predicate)
  Filters a sequence of values based on a predicate.
• Where (IQueryable<TSource> source, Expression<Func<TSource, int, bool>> predicate)
  Filters a sequence of values based on a predicate. The element's index is used in the predicate's evaluation.
• Zip (IQueryable<TFirst> first, IQueryable<TSecond> second, Expression<Func<TFirst, TSecond, TResult>> resultSelector)
  Zips together two sequences.

using System;
using System.Linq;
using System.Collections.Generic;

// Assume this is your data source, which implements IQueryable
IEnumerable<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

// Using Queryable.Where to filter even numbers
IQueryable<int> evenNumbersQuery = numbers.AsQueryable().Where(n => n % 2 == 0);

// To execute the query and get results (e.g., if this were a database query)
// In this simple example, it will just enumerate the IEnumerable
var result = evenNumbersQuery.ToList();

// result will contain: [2, 4, 6, 8, 10]