String array contains c # linq select where

Enumerable.Select Method

Projects each element of a sequence into a new form by incorporating the element's index.

Type parameters


The type of the elements of.


The type of the value returned by.



A sequence of values ​​to invoke a transform function on.


A transform function to apply to each source element; the second parameter of the function represents the index of the source element.



An IEnumerable whose elements are the result of invoking the transform function on each element of.



The following code example demonstrates how to use Select (IEnumerable , Func ) to project over a sequence of values ​​and use the index of each element.


This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its method directly or by using in Visual C # or in Visual Basic.

The first argument to represents the element to process. The second argument to represents the zero-based index of that element in the source sequence. This can be useful if the elements are in a known order and you want to do something with an element at a particular index, for example. It can also be useful if you want to retrieve the index of one or more elements.

This projection method requires the transform function, to produce one value for each value in the source sequence,. If returns a value that is itself a collection, it is up to the consumer to traverse the subsequences manually. In such a situation, it might be better for your query to return a single coalesced sequence of values. To achieve this, use the Select Many method instead of Select. Although works similarly to, it differs in that the transform function returns a collection that is then expanded by before it is returned.