Here I would like to describe how to use a LINQ query and describe how to query dataset data.

I will describe the following points. I have described all points using a simple example.

(A) Select: It's a Projection operator, it selects a value from a collection.

In my example my data source is a dataset. I need to describe both a lambda expression and a simple query.

1. Here a simple query is like SQL query Example(Select * from tablename):

(1) var data = from s in MyData().Tables[0].AsEnumerable()

(2) select s;

(3) foreach (var mydata in data)

(4) {

(5) Console.WriteLine("EmployeeID:" + mydata["Employeeid"] + "," + "Name:" + mydata["Name"] +
"Gender:" + mydata["Gender"] + ",Age:" +
mydata["Age"] +

(6) ",Qualification:" + mydata["Qualification"] + ",FatherName:" + mydata["FatherName"] + ",Address:"
 + mydata["Address"] + Environment.NewLine);

2. Here I have selected all data using a lambda expression.

Console.WriteLine("-----------Simple Query to=>select all column data using Lambda Expression of linq----------------");

var data2 = MyData().Tables[0].AsEnumerable().Select(k => k);

foreach (var mydata in data2)

{

Console.WriteLine("EmployeeID:" + mydata["Employeeid"] + "," + "Name:" + mydata["Name"] + "Gender:"
+ mydata["Gender"] + ",Age:" + mydata["Age"] +

",Qualification:" + mydata["Qualification"] + ",FatherName:" + mydata["FatherName"] + ",Address:" +
mydata["Address"] + Environment.NewLine);

}

3. Here select a specific column like SQL query (select column1,column2 from tablename):

//Like Sql query =>select columnname1,columnname2 from tablename

Console.WriteLine("--------------------------Simple Query to=> select specific column data--
------------------
--------");

var data1 = from p in MyData().Tables[0].AsEnumerable()

select new { Employeeid = p["Employeeid"].ToString(), Name = p["Name"].ToString() };

foreach (var mydata1 in data1)

{

Console.WriteLine(mydata1.Employeeid + "," + mydata1.Name);

}

4. Here I need to convert the query above into a lambda expression.

//Using Lambda expression=>Like Sql query =>select columnname1,columnname2 from tablename

Console.WriteLine("-----------Simple Query to=>select all column data using Lambda Expression of linq---
-------------");

var data3 = MyData().Tables[0].AsEnumerable().Select(k => new { Employeeid = k["Employeeid"], Name
= k["Name"] });

foreach (var mydata1 in data3)

{

Console.WriteLine(mydata1.Employeeid + "," + mydata1.Name);

}

5. Here I need to show how to convert a SQL Case statement inro a LINQ.

//Using Lambda expression=>Like Sql query=>use case in Sql query

//=>select columnname1,columnname2,case when columnname3 = 1 then 'Female' when columnname3
= 2 then 'Male' from tablename

Console.WriteLine("-----------Simple Query to=>select all column data using Lambda Expression of linq----------------");

var data4 = MyData().Tables[0].AsEnumerable().Select(k => new

{

Employeeid = k["Employeeid"],

Name = k["Name"],

Gender = k["Gender"].ToString() == "1" ? "Female" : k["Gender"].ToString() == "2" ? "Male" : ""

});

foreach (var mydata1 in data4)

{

Console.WriteLine(mydata1.Employeeid + "," + mydata1.Name + "," + mydata1.Gender);

In the next article I need to describe the Restriction Operator.