Method Case

Case<TValue, TResult>(Func<TValue>, IDictionary<TValue, IEnumerable<TResult>>)

Returns a sequence from a dictionary based on the result of evaluating a selector function.

Declaration

public static IEnumerable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IEnumerable<TResult>> sources) where TValue : notnull

Parameters

Type	Name	Description
Func<TValue>	selector	Selector function used to pick a sequence from the given sources.
IDictionary<TValue, IEnumerable<TResult>>	sources	Dictionary mapping selector values onto resulting sequences.

Returns

Type	Description
IEnumerable<TResult>	The source sequence corresponding with the evaluated selector value; otherwise, an empty sequence.

Type Parameters

Name	Description
TValue	Type of the selector value.
TResult	Result sequence element type.

Remarks

selector is not evaluated until enumeration. The value returned will be used to select a sequence from sources; enumeration will continue with items from that sequence.

If the value returned by selector is not present in sources, the resulting sequence will be empty.

Examples

The following code example demonstrates how to select which sequence to return values from, using Case.

var sequences = Enumerable.Range(1, 5)
    .ToDictionary(
        x => x,
        x => Enumerable.Range(1, x));

// Use a function to select which sequence to return values from.
var selector = 1;
var result = SuperEnumerable
    .Case(
        () => selector,
        sequences);

Console.WriteLine($"Selector: {selector}; result.Count(): {result.Count()}.");
selector = 4;
Console.WriteLine($"Selector: {selector}; result.Count(): {result.Count()}.");
selector = 2;
Console.WriteLine($"Selector: {selector}; result.Count(): {result.Count()}.");

// This code produces the following output:
// Selector: 1; result.Count(): 1.
// Selector: 4; result.Count(): 4.
// Selector: 2; result.Count(): 2.

Exceptions

Type	Condition
ArgumentNullException	selector or sources is null.
ArgumentNullException	(Thrown lazily) The sequence in sources selected by the result of selector is null.

Case<TValue, TResult>(Func<TValue>, IDictionary<TValue, IEnumerable<TResult>>, IEnumerable<TResult>)

Returns a sequence from a dictionary based on the result of evaluating a selector function.

Declaration

public static IEnumerable<TResult> Case<TValue, TResult>(Func<TValue> selector, IDictionary<TValue, IEnumerable<TResult>> sources, IEnumerable<TResult> defaultSource) where TValue : notnull

Parameters

Type	Name	Description
Func<TValue>	selector	Selector function used to pick a sequence from the given sources.
IDictionary<TValue, IEnumerable<TResult>>	sources	Dictionary mapping selector values onto resulting sequences.
IEnumerable<TResult>	defaultSource	Default sequence to return in case there's no corresponding source for the computed selector value.

Returns

Type	Description
IEnumerable<TResult>	The source sequence corresponding with the evaluated selector value; otherwise, the defaultSource sequence.

Type Parameters

Name	Description
TValue	Type of the selector value.
TResult	Result sequence element type.

Remarks

selector is not evaluated until enumeration. The value returned will be used to select a sequence from sources; enumeration will continue with items from that sequence.

Examples

The following code example demonstrates how to select which sequence to return values from, using Case.

var sequences = Enumerable.Range(1, 5)
    .ToDictionary(
        x => x,
        x => Enumerable.Range(1, x));

// Use a function to select which sequence to return values from.
var selector = 1;
var result = SuperEnumerable
    .Case(
        () => selector,
        sequences,
        Enumerable.Range(1, 100));

Console.WriteLine($"Selector: {selector}; result.Count(): {result.Count()}.");
selector = 4;
Console.WriteLine($"Selector: {selector}; result.Count(): {result.Count()}.");
selector = 20;
Console.WriteLine($"Selector: {selector}; result.Count(): {result.Count()}.");

// This code produces the following output:
// Selector: 1; result.Count(): 1.
// Selector: 4; result.Count(): 4.
// Selector: 20; result.Count(): 100.

Exceptions

Type	Condition
ArgumentNullException	selector, sources or defaultSource is null.
ArgumentNullException	(Thrown lazily) The sequence in sources selected by the result of selector is null.