Filtering Data (C#)

Filtering refers to the operation of restricting the result set to contain only those elements that satisfy a specified condition. It is also known as selection.

The following illustration shows the results of filtering a sequence of characters. The predicate for the filtering operation specifies that the character must be 'A'.

Diagram that shows a LINQ filtering operation

The standard query operator methods that perform selection are listed in the following section.


Method Name Description C# Query Expression Syntax More Information
OfType Selects values, depending on their ability to be cast to a specified type. Not applicable. Enumerable.OfType

Where Selects values that are based on a predicate function. where Enumerable.Where


Query Expression Syntax Example

The following example uses the where clause to filter from an array those strings that have a specific length.

string[] words = { "the", "quick", "brown", "fox", "jumps" };  
IEnumerable<string> query = from word in words  
                            where word.Length == 3  
                            select word;  
foreach (string str in query)  
/* This code produces the following output:  

See also