Method Fold

Fold<T, TResult>(IEnumerable<T>, Func<T, TResult>)

Returns the result of applying a function to a sequence of 1 element.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 1 element using Fold.

var sequence = Enumerable.Range(1, 1);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a) => a);

Console.WriteLine(result);

// This code produces the following output:
// 1

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 1 element.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, TResult>)

Returns the result of applying a function to a sequence of 2 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 2 elements using Fold.

var sequence = Enumerable.Range(1, 2);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b) => a + b);

Console.WriteLine(result);

// This code produces the following output:
// 3

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 2 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, TResult>)

Returns the result of applying a function to a sequence of 3 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 3 elements using Fold.

var sequence = Enumerable.Range(1, 3);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c) => a + b + c);

Console.WriteLine(result);

// This code produces the following output:
// 6

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 3 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 4 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 4 elements using Fold.

var sequence = Enumerable.Range(1, 4);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d) => a + b + c + d);

Console.WriteLine(result);

// This code produces the following output:
// 10

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 4 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 5 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 5 elements using Fold.

var sequence = Enumerable.Range(1, 5);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e) => a + b + c + d + e);

Console.WriteLine(result);

// This code produces the following output:
// 15

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 5 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 6 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 6 elements using Fold.

var sequence = Enumerable.Range(1, 6);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f) => a + b + c + d + e + f);

Console.WriteLine(result);

// This code produces the following output:
// 21

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 6 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 7 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 7 elements using Fold.

var sequence = Enumerable.Range(1, 7);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g) =>
        a + b + c + d + e + f + g);

Console.WriteLine(result);

// This code produces the following output:
// 28

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 7 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 8 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 8 elements using Fold.

var sequence = Enumerable.Range(1, 8);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g, h) =>
        a + b + c + d + e + f + g + h);

Console.WriteLine(result);

// This code produces the following output:
// 36

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 8 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 9 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 9 elements using Fold.

var sequence = Enumerable.Range(1, 9);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g, h, i) =>
        a + b + c + d + e + f + g + h + i);

Console.WriteLine(result);

// This code produces the following output:
// 45

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 9 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 10 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 10 elements using Fold.

var sequence = Enumerable.Range(1, 10);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g, h, i, j) =>
        a + b + c + d + e + f + g + h + i + j);

Console.WriteLine(result);

// This code produces the following output:
// 55

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 10 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 11 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 11 elements using Fold.

var sequence = Enumerable.Range(1, 11);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g, h, i, j, k) =>
        a + b + c + d + e + f + g + h + i + j + k);

Console.WriteLine(result);

// This code produces the following output:
// 66

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 11 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 12 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 12 elements using Fold.

var sequence = Enumerable.Range(1, 12);
            
// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g, h, i, j, k, l) =>
        a + b + c + d + e + f + g + h + i + j + k + l);

Console.WriteLine(result);

// This code produces the following output:
// 78

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 12 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 13 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 13 elements using Fold.

var sequence = Enumerable.Range(1, 13);

// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g, h, i, j, k, l, m) =>
        a + b + c + d + e + f + g + h + i + j + k + l + m);

Console.WriteLine(result);

// This code produces the following output:
// 91

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 13 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 14 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 14 elements using Fold.

var sequence = Enumerable.Range(1, 14);

// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g, h, i, j, k, l, m, n) =>
        a + b + c + d + e + f + g + h + i + j + k + l + m + n);

Console.WriteLine(result);

// This code produces the following output:
// 105

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 14 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 15 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 15 elements using Fold.

var sequence = Enumerable.Range(1, 15);

// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) =>
        a + b + c + d + e + f + g + h + i + j + k + l + m + n + o);

Console.WriteLine(result);

// This code produces the following output:
// 120

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 15 elements.

Fold<T, TResult>(IEnumerable<T>, Func<T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, TResult>)

Returns the result of applying a function to a sequence of 16 elements.

Declaration

public static TResult Fold<T, TResult>(this IEnumerable<T> source, Func<T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, TResult> folder)

Parameters

Type	Name	Description
IEnumerable<T>	source	The sequence of items to fold.
Func<T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, TResult>	folder	Function to apply to the elements in the sequence.

Returns

Type	Description
TResult	The folded value returned by folder.

Type Parameters

Name	Description
T	Type of element in the source sequence
TResult	Type of the result

Remarks

This operator uses immediate execution and buffers as many items of the source sequence as necessary.

Examples

The following code example demonstrates how to apply a projection to a sequence of 16 elements using Fold.

var sequence = Enumerable.Range(1, 16);

// Fold a sequence into a single value.
var result = sequence
    .Fold((a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p) =>
        a + b + c + d + e + f + g + h + i + j + k + l + m + n + o + p);

Console.WriteLine(result);

// This code produces the following output:
// 136

Exceptions

Type	Condition
ArgumentNullException	source or folder is null.
InvalidOperationException	source does not contain exactly 16 elements.