Using C# LINQ - A Practical Overview


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Methods - Calculate a new sequence

These LINQ methods can be used to create a new IEnumerable<T> result sequence based on the values in the source sequence.

NOTE: Same comment as before. If I state that a method "returns a sequence," this is not technically true. The methods in this chapter return an IEnumerable<T>, which is a generator (or an iterator) that can provide a sequence on demand.

Cast<U>() method

The Cast<U>() method casts each element of a source IEnumerable<T> sequence, individually, to a base or derived type U and returns a sequence containing all of the resultant elements.

NOTE: If the source type T can't be cast to the result type U then the cast will fail with an InvalidCastException.

IEnumerable<IComparable> values = new List<IComparable> { 2, 3, 4 };
// Will return { 2, 3, 4 }
// The elements in the collection are the same,
// but the collection type is different
IEnumerable<int> result = values.Cast<int>();
IEnumerable<string> strings = new List<string> { "one", "two", "three" };
// Will throw InvalidCastException
IEnumerable<int> result = strings.Cast<int>();

NOTE: Casting to a more-derived type is always a dubious activity, and typically indicates a failure in polymorphic design. Cast<U> should more likely be used to cast to a less-derived, base type.

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