LINQ Operators : Filtering Operators

LINQ operators are a collection of methods that form the heart and soul of the LINQ(Language Integrated Query). The best thing of these operators is how they can execute against different data sources. You can use these operators not only to query object in memory but you can use same operators to query object stored in relational database, in XML, datasets and more.

 

Standard LINQ Operators:

We can categories the LINQ operators into following area of functionality

• Filtering
• Projecting
• Ordering
• Grouping 
• Conversions 
• Joining
• Aggregation
• Elements 
• Sets

Filtering Operators:

Where and OfType are two filtering operators in LINQ .

1.  Where: The Where can used to filter a set of items. This is also called restriction operator because it restricts a set of items
   
   //array of numbers 
   int[] numbers={2,4,5,6,7,9,10};  
   //select numbers which are greater than 2

   var number = from n in numbers

                        where n > 2 && n < 7

                  select n;       /*output 4, 5, 6*/


2. OfType: The OfType can used to filter values based on the type (can use on IEnumerable). For   example if we have an array of objects which contains strings, decimal, float and numbers or any other. We can use OfType operator to extract only strings or any particular type of values.
   
   ArrayList list = new ArrayList();

   list.Add("Dash");

   list.Add(new object());
   list.Add("Skitty");
   list.Add(new object()); 
   var query = from name in list.OfType<string>()

                      select name; /* output Dash, Skitty*/

      To be continued......

Happy Reading!!