Method RandomSubset

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RandomSubset<T>(IEnumerable<T>, int)

Returns a sequence of a specified size of random elements from the original sequence.

Declaration
public static IEnumerable<T> RandomSubset<T>(this IEnumerable<T> source, int subsetSize)
Parameters
Type Name Description
IEnumerable<T> source

The sequence from which to return random elements.
int subsetSize

The size of the random subset to return.
Returns
Type Description
IEnumerable<T>

A random sequence of elements in random order from the original sequence.
Type Parameters
Name Description
T

The type of source sequence elements.
Remarks

This method is implemented by using deferred execution. However, source will be consumed in it's entirety immediately when first element of the returned sequence is consumed.

Examples

The following code example demonstrates how to get a random subset of a sequence using RandomSubset.

var sequence = Enumerable.Range(1, 10);

// get a random subset of the above sequence
var result = sequence.RandomSubset(4);

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// One possible output of the above sequence:
// (each run will have different results)
// [3, 6, 7, 5]
Exceptions
Type Condition
ArgumentNullException

source is null.
ArgumentOutOfRangeException

subsetSize is negative or larger than the length of source.
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RandomSubset<T>(IEnumerable<T>, int, Random)

Returns a sequence of a specified size of random elements from the original sequence.

Declaration
public static IEnumerable<T> RandomSubset<T>(this IEnumerable<T> source, int subsetSize, Random rand)
Parameters
Type Name Description
IEnumerable<T> source

The sequence from which to return random elements.
int subsetSize

The size of the random subset to return.
Random rand

A random generator used as part of the selection algorithm.
Returns
Type Description
IEnumerable<T>

A random sequence of elements in random order from the original sequence.
Type Parameters
Name Description
T

The type of source sequence elements.
Remarks

This method is implemented by using deferred execution. However, source will be consumed in it's entirety immediately when first element of the returned sequence is consumed.

Examples

The following code example demonstrates how to get a random subset of a sequence using RandomSubset.

var sequence = Enumerable.Range(1, 10);

// get a random subset of the above sequence
var result = sequence.RandomSubset(4, new Random(Seed: 5));

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [7, 8, 2, 6]
Exceptions
Type Condition
ArgumentNullException

source or rand is null.
ArgumentOutOfRangeException

subsetSize is negative or larger than the length of source.