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Getting Started with Linq Queries


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Getting Started with Linq Queries

Hi everyone in this blog I’m explaining about linq query.

Introduction:

Language-Integrated Query (LINQ) is a set of features introduced in Visual Studio 2008 that extends powerful query capabilities to the language syntax of C# and Visual Basic. LINQ introduces standard, easily-learned patterns for querying and updating data, and the technology can be extended to support potentially any kind of data store. Visual Studio includes LINQ provider assemblies that enable the use of LINQ with .NET Framework collections, SQL Server databases, ADO.NET Datasets, and XML documents.

Basic Query:

// To achieve  Select * From ProductMst  you need to write following linq Query

  var Result1 = from p in db.ProductMst

                 select p;

// to achieve Select ProductID, ProductName, Price from ProductMst you need to write following linq Query

    var Result2 = from p in db.ProductMst

                 Select new {

                     p.ProductID,

                     p.ProductName,

                     p.Price

                 };

 

Where Clause Query:

// to achieve Select * From ProductMst Where ProductID = 1 you need to write following linq Query

    var Result3 = from p in db.ProductMst

                 Where p.ProductID == 1

                 Select p;

 

// to achieve Select * From ProductMst Where SupplierId =2 and Price > 10 you need to write following linq Query

    var Result4 = from p in db.ProductMst

                 Where p.SupplierID == 2 && p.Price > 10

                 Select p;

 

 

// to achieve Select * From ProductMst Where SupplierId =2 Or SupplierId=5 you need to write following linq Query

    var Result5 = from p in db.ProductMst

                 Where p.SupplierID == 2 || p.SupplierID == 5

                 Select p;

 

Order By Query:

//To achieve   Select * From ProductMst Order By ProductId you need to write following linq Query

    var Result6 = from p in db.ProductMst

                 orderby p.ProductID

                 select p;

 

// to achieve Select * From ProductMst Order By ProductId Desc you need to write following linq Query

    var Result7 = from p in db.ProductMst

                 orderby p.ProductID descending

                 select p;

 

// to achieve Select * From ProductMst Order By CategoryId, Price Desc you need to write following linq Query

    var Result8 = from p in db.ProductMst

                 orderby p.CategoryID, p.Price descending

                 Select p;

 

Top Query:

//To achieve Select Top 5 * From ProductMst you need to write following linq Query

    var Result9 = (from p in db.ProductMst

                 Select p).Take (5);

 

//To achieve Select Top 1 * From ProductMst you need to write following linq Query

    var Result10 = (from p in db.ProductMst

                   Select p).Take (1);

     or

 

    var Result11 = (from p in db.ProductMst

                   select p).First();

 

Distinct Query:

//To achieve Select Distinct CategoryId From ProductMst you need to write following linq Query

 

    var Result13 = (from p in db.ProductMst

                   Select p.CategoryID).Distinct ();

 

Group By Query:

//To achieve Select CategoryId, Count(CategoryID) As FieldName From ProductMst Group By CategoryId you need to write following linq Query

    var Result14 = from p in db.ProductMst

                  Group p by p.CategoryID into g

                  Select new {

                      CategoryId = g.Key,

                      FieldName = g.Count()

                  };

 

//To achieve Select CategoryId, Avg(UnitPrice) As NewField From ProductMst Group By CategoryId you need to write follofing linq Query

    var Result15 = from p in db.ProductMst

                  group p by p.CategoryID into g

                  Select new {

                      CategoryId = g.Key,

                      FieldName = g.Average(S => S.Price)

                  };

 

Union Query:

//To achieve Select * From ProductMst Where CategoryId =1 union Select *  From ProductMst Where CategoryId = 2 you need to write follofing linq Query

    var Result17 = (from p in db.ProductMst

                   Where p.CategoryID == 1

                   Select p).Union (

                       From m in db.ProductMst

                       Where m.CategoryID == 2

                       Select m

                   );

 

in my next post i'll explain about Introduction of Troubleshooting


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