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C# Skip and SkipWhile ExamplesInvoke Skip and SkipWhile to return elements only after a certain number are encountered.
Skip. This is an extension method. It returns only the elements following a certain number of initial elements that must be ignored.
Skip namespace. Skip() is found in the System.Linq namespace. It is useful in programs that selectively process elements. SkipWhile is also available.
Take, TakeWhile
First example. Please include the System.Linq namespace. This provides extensions that act upon IEnumerable implementations (like arrays and Lists).
Extension
IEnumerable
Step 1 The integer array is allocated and immediately filled with six 32-bit signed integers.
Step 2 The argument to Skip is the int 2. This will pass over the first 2 elements and only return those that follow.
Step 3 The argument here is 4. The second loop in the example repeats this procedure but for 4 elements.
Info No action is taken until you loop over the resulting variable. Skip() takes effect when the foreach queries for results.
Foreach
C# program that uses Skip method from LINQ
using System; using System.Linq; class Program { static void Main() { // Step 1: create array for demonstration. int[] array = { 1, 3, 5, 7, 9, 11 }; // Step 2: get collection of all elements except first two. var items1 = array.Skip(2); foreach (var value in items1) { Console.WriteLine("SKIP 2: {0}", value); } // Step 3: call Skip again but skip the first 4 elements. var items2 = array.Skip(4); foreach (var value in items2) { Console.WriteLine("SKIP 4: {0}", value); } } }
SKIP 2: 5 SKIP 2: 7 SKIP 2: 9 SKIP 2: 11 SKIP 4: 9 SKIP 4: 11
SkipWhile. This method skips over elements matching a condition. With SkipWhile you need to specify a Func condition to skip over values with.
Start We declare an array that has several values in it. The first 3 elements are less than 10.
And We call SkipWhile with a Func that returns true for elements less than 10. The first 3 elements in the array are skipped.
C# program that shows SkipWhile method
using System; using System.Linq; class Program { static void Main() { int[] array = { 1, 3, 5, 10, 20 }; var result = array.SkipWhile(element => element < 10); foreach (int value in result) { Console.WriteLine(value); } } }
10 20
Practical uses. In your program, you might have some reason to remove elements at the start of a collection that begin with a certain letter or have a property set to a certain value.
Tip You could use SkipWhile. Then you could call ToArray to ToList to convert the IEnumerable back into an array or List.
ToArray
ToList
Array
List
Discussion. The Skip extension method is a generic method, which means it requires a type parameter. The C# compiler can infer the correct type parameter.
Generic Class, Method
Info The Skip extension method internally allocates a new class that is compiler-generated and stores the state of the Skip operation.
Tip This indicates that using a for-loop and starting at the desired index will be much faster.
For
Tip 2 Often you would use Skip on a collection that cannot be accessed by specific indexes.
Skip and Take. You can also use the Skip extension method in query method chains. Often you may want to combine it with Take, either before the Skip or after.
Note The Take extension method specifies that you only want to access the following several elements.
So If you want the middle elements in a sequence, you can Skip over the first several and then Take the part you want.
Take, TakeWhile
A summary. Skip serves to "pass over" several elements in any class that implements the IEnumerable interface. It is most useful on more complex collections or queries.
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