LINQ TO Object Sample

LINQ:

          LINQ stands for “Language Integrated Query”.

Different datastores has got different query languages. Microsoft’s idea is providing one query language syntax to all the datastors to make developer job easier.

This lead to invention of LINQ with .NET3.5

LINQ is a concept of performing queries based on language syntax.

LINQ syntax:

           var res= from variablename in source

                           where condition

                           group by...

                           order by...

                           select variablename;

     source can be database, object, xml document.

LINQ can be classified into 3 types:

   1) LINQ to Object.

   2) LINQ to SQL.

   3) LINQ to XML.

LINQ to object:

           Applying linq query expression to object is called “Linq to object”.

 Ex:

      Int[]a={2,5,6,7,1,3};

//Display number>=5

      var res = from aa in a

                     where aa>=5

                     order by aa descending

                     select aa;

LINQ Samples: Restriction Operators

Where - Simple 1

This sample uses where to find all elements of an array less than 5.

public void Linq1()

{

    int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var lowNums =

        from n in numbers

        where n < 5

        select n;

    Console.WriteLine("Numbers < 5:");

    foreach (var x in lowNums)

    {

        Console.WriteLine(x);

    }

}

Result

Numbers < 5:
4
1
3
2
0

Where - Indexed

This sample demonstrates an indexed Where clause that returns digits whose name is shorter than their value.

public void Linq5()

{

    string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var shortDigits = digits.Where((digit, index) => digit.Length < index);

    Console.WriteLine("Short digits:");

    foreach (var d in shortDigits)

    {

        Console.WriteLine("The word {0} is shorter than its value.", d);

    }

}

Result

Short digits:
The word five is shorter than its value.
The word six is shorter than its value.
The word seven is shorter than its value.
The word eight is shorter than its value.
The word nine is shorter than its value.