Sunday, 25 August 2013

Linq - Parallel Query and Cross Apply


In this article we are going to see how to create a parallel query execution and how to do the cross apply in Linq.

Parallel Query Execution :

/* Generate Even Numbers using parallel Extension. Execution of query in parallel to generate the Even number */
You can see the output of this program that the even numbers are print in UnOrder manner due to the parallel execution of query.

IEnumerable<int> values = ParallelEnumerable.Range(1, 40).Where(x => x % 2 == 0);
foreach (int i in values)
   Console.WriteLine(i);

Output:
2
4
22
32
6
12
24
34
8
14
26
36
10
16
28
38
18
30
40
20

Cross Apply:
Some times we have a requirement that cross apply the collection and get the value in another collection.
this can be done by SelectMany of one collection for each value of select in another collection.


  /* Cross Apply in Linq */
  var list1 = new List<string>() { "PC", "LAP", "TAB" };
  var list2 = new List<string>() { "HomeTheatre", "Graphics Card", "Moderm" };

  var cross = list1.SelectMany(x => list2.Select(y => x + "+" + y));
   foreach (string crs in cross)
        Console.WriteLine(crs);


Output:

PC+HomeTheatre
PC+Graphics Card
PC+Moderm
LAP+HomeTheatre
LAP+Graphics Card
LAP+Moderm
TAB+HomeTheatre
TAB+Graphics Card

TAB+Moderm


From this article I hope that you can learn the some basics parallel query execution and how to do the cross apply of Linq.

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