Method ToArrayByIndex

ToArrayByIndex<T>(IEnumerable<T>, Func<T, int>)

Creates an array from an IEnumerable<T> where a function is used to determine the index at which an element will be placed in the array.

Declaration

public static T?[] ToArrayByIndex<T>(this IEnumerable<T> source, Func<T, int> indexSelector)

Parameters

Type	Name	Description
IEnumerable<T>	source	The source sequence for the array.
Func<T, int>	indexSelector	A function that maps an element to its index.

Returns

Type	Description
T[]	An array that contains the elements from source. The size of the array will be as large as the highest index returned by the indexSelector plus 1.

Type Parameters

Name	Description
T	The type of the element in source.

Remarks

This method forces immediate query evaluation. It should not be used on infinite sequences. If more than one element maps to the same index then the latter element overwrites the former in the resulting array.

Examples

The following code example demonstrates how to transform a sequence into an array using indices using ToArrayByIndex.

var sequence = new[] { "foo", "bar", "alp", "car", };

// Transform a sequence by index
var result = sequence
    .ToArrayByIndex(c => c[0] - 'a');

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

// This code produces the following output:
// [alp, bar, car, , , foo]

Exceptions

Type	Condition
ArgumentNullException	source or indexSelector is null.
ArgumentOutOfRangeException	An index returned by indexSelector is less than 0.

ToArrayByIndex<T, TResult>(IEnumerable<T>, Func<T, int>, Func<T, TResult>)

Creates an array from an IEnumerable<T> where a function is used to determine the index at which an element will be placed in the array. The elements are projected into the array via an additional function.

Declaration

public static TResult?[] ToArrayByIndex<T, TResult>(this IEnumerable<T> source, Func<T, int> indexSelector, Func<T, TResult> resultSelector)

Parameters

Type	Name	Description
IEnumerable<T>	source	The source sequence for the array.
Func<T, int>	indexSelector	A function that maps an element to its index.
Func<T, TResult>	resultSelector	A function to project a source element into an element of the resulting array.

Returns

Type	Description
TResult[]	An array that contains the projected elements from source. The size of the array will be as large as the highest index returned by the indexSelector plus 1.

Type Parameters

Name	Description
T	The type of the element in source.
TResult	The type of the element in the resulting array.

Remarks

This method forces immediate query evaluation. It should not be used on infinite sequences. If more than one element maps to the same index then the latter element overwrites the former in the resulting array.

Examples

The following code example demonstrates how to transform a sequence into an array using indices using ToArrayByIndex.

var sequence = new[] { "foo", "bar", "alp", "car", };

// Transform a sequence by index
var result = sequence
    .ToArrayByIndex(c => c[0] - 'a', c => $"{c[0] - 'a'}:{c}");

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

// This code produces the following output:
// [0:alp, 1:bar, 2:car, , , 5:foo]

Exceptions

Type	Condition
ArgumentNullException	source, indexSelector, or resultSelector is null.
ArgumentOutOfRangeException	An index returned by indexSelector is less than 0.

ToArrayByIndex<T, TResult>(IEnumerable<T>, Func<T, int>, Func<T, int, TResult>)

Creates an array from an IEnumerable<T> where a function is used to determine the index at which an element will be placed in the array. The elements are projected into the array via an additional function.

Declaration

public static TResult?[] ToArrayByIndex<T, TResult>(this IEnumerable<T> source, Func<T, int> indexSelector, Func<T, int, TResult> resultSelector)

Parameters

Type	Name	Description
IEnumerable<T>	source	The source sequence for the array.
Func<T, int>	indexSelector	A function that maps an element to its index.
Func<T, int, TResult>	resultSelector	A function to project a source element into an element of the resulting array.

Returns

Type	Description
TResult[]	An array that contains the projected elements from source. The size of the array will be as large as the highest index returned by the indexSelector plus 1.

Type Parameters

Name	Description
T	The type of the element in source.
TResult	The type of the element in the resulting array.

Remarks

This method forces immediate query evaluation. It should not be used on infinite sequences. If more than one element maps to the same index then the latter element overwrites the former in the resulting array.

Examples

The following code example demonstrates how to transform a sequence into an array using indices using ToArrayByIndex.

var sequence = new[] { "foo", "bar", "alp", "car", };

// Transform a sequence by index
var result = sequence
    .ToArrayByIndex(c => c[0] - 'a', (c, i) => $"{i}:{c}");

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

// This code produces the following output:
// [0:alp, 1:bar, 2:car, , , 5:foo]

Exceptions

Type	Condition
ArgumentNullException	source, indexSelector, or resultSelector is null.
ArgumentOutOfRangeException	An index returned by indexSelector is less than 0.

ToArrayByIndex<T>(IEnumerable<T>, int, Func<T, int>)

Creates an array of user-specified length from an IEnumerable<T> where a function is used to determine the index at which an element will be placed in the array.

Declaration

public static T?[] ToArrayByIndex<T>(this IEnumerable<T> source, int length, Func<T, int> indexSelector)

Parameters

Type	Name	Description
IEnumerable<T>	source	The source sequence for the array.
int	length	The (non-negative) length of the resulting array.
Func<T, int>	indexSelector	A function that maps an element to its index.

Returns

Type	Description
T[]	An array of size length that contains the elements from source.

Type Parameters

Name	Description
T	The type of the element in source.

Remarks

This method forces immediate query evaluation. It should not be used on infinite sequences. If more than one element maps to the same index then the latter element overwrites the former in the resulting array.

Examples

The following code example demonstrates how to transform a sequence into an array using indices using ToArrayByIndex.

var sequence = new[] { "foo", "bar", "alp", "car", };

// Transform a sequence by index
var result = sequence
    .ToArrayByIndex(26, c => c[0] - 'a');

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

// This code produces the following output:
// [alp, bar, car, , , foo, , , , , , , , , , , , , , , , , , , , ]

Exceptions

Type	Condition
ArgumentNullException	source or indexSelector is null.
ArgumentOutOfRangeException	length is less than 0. -or- An index returned by indexSelector is invalid for an array of size length.

ToArrayByIndex<T, TResult>(IEnumerable<T>, int, Func<T, int>, Func<T, TResult>)

Creates an array of user-specified length from an IEnumerable<T> where a function is used to determine the index at which an element will be placed in the array. The elements are projected into the array via an additional function.

Declaration

public static TResult?[] ToArrayByIndex<T, TResult>(this IEnumerable<T> source, int length, Func<T, int> indexSelector, Func<T, TResult> resultSelector)

Parameters

Type	Name	Description
IEnumerable<T>	source	The source sequence for the array.
int	length	The (non-negative) length of the resulting array.
Func<T, int>	indexSelector	A function that maps an element to its index.
Func<T, TResult>	resultSelector	A function to project a source element into an element of the resulting array.

Returns

Type	Description
TResult[]	An array of size length that contains the projected elements from source.

Type Parameters

Name	Description
T	The type of the element in source.
TResult	The type of the element in the resulting array.

Remarks

This method forces immediate query evaluation. It should not be used on infinite sequences. If more than one element maps to the same index then the latter element overwrites the former in the resulting array.

Examples

The following code example demonstrates how to transform a sequence into an array using indices using ToArrayByIndex.

var sequence = new[] { "foo", "bar", "alp", "car", };

// Transform a sequence by index
var result = sequence
    .ToArrayByIndex(26, c => c[0] - 'a', (c, i) => $"{i}:{c}");

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

// This code produces the following output:
// [0:alp, 1:bar, 2:car, , , 5:foo, , , , , , , , , , , , , , , , , , , , ]

Exceptions

Type	Condition
ArgumentNullException	source, indexSelector, resultSelector is null.
ArgumentOutOfRangeException	length is less than 0. -or- An index returned by indexSelector is invalid for an array of size length.

ToArrayByIndex<T, TResult>(IEnumerable<T>, int, Func<T, int>, Func<T, int, TResult>)

Creates an array of user-specified length from an IEnumerable<T> where a function is used to determine the index at which an element will be placed in the array. The elements are projected into the array via an additional function.

Declaration

public static TResult?[] ToArrayByIndex<T, TResult>(this IEnumerable<T> source, int length, Func<T, int> indexSelector, Func<T, int, TResult> resultSelector)

Parameters

Type	Name	Description
IEnumerable<T>	source	The source sequence for the array.
int	length	The (non-negative) length of the resulting array.
Func<T, int>	indexSelector	A function that maps an element to its index.
Func<T, int, TResult>	resultSelector	A function to project a source element into an element of the resulting array.

Returns

Type	Description
TResult[]	An array of size length that contains the projected elements from the input sequence.

Type Parameters

Name	Description
T	The type of the element in source.
TResult	The type of the element in the resulting array.

Remarks

This method forces immediate query evaluation. It should not be used on infinite sequences. If more than one element maps to the same index then the latter element overwrites the former in the resulting array.

Examples

The following code example demonstrates how to transform a sequence into an array using indices using ToArrayByIndex.

var sequence = new[] { "foo", "bar", "alp", "car", };

// Transform a sequence by index
var result = sequence
    .ToArrayByIndex(26, c => c[0] - 'a', c => $"{c[0] - 'a'}:{c}");

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

// This code produces the following output:
// [0:alp, 1:bar, 2:car, , , 5:foo, , , , , , , , , , , , , , , , , , , , ]

Exceptions

Type	Condition
ArgumentNullException	source, indexSelector, resultSelector is null.
ArgumentOutOfRangeException	length is less than 0. -or- An index returned by indexSelector is invalid for an array of size length.