Linq in c#

Introduction

In the last article, I have explained, how to work on collection with the help of "Linq", Now its time to move towards some new thing about "Linq", I think you all know about the "properties".

Here, I am giving an example to explain "Linq" and "Properties" breifly.
Just, follow the following steps, and make fun with "properties" and "Linq".

Step 1 

In VS, File->New->Project->ClassLibrary(take name of it like "student.cs")->ok

Step 2

Write code like:

Here I simply create properties for student class.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace student

{

    public class Class1

    {

        private int stuRollNo;

        private string stuName;

        private int stuAge;

        public int StuAge

        {

            get { return stuAge; }

            set { stuAge = value; }

        }

        public string StuName

        {

            get { return stuName; }

            set { stuName = value; }

        }

        public int StuRollNo

        {

            get { return stuRollNo; }

            set { stuRollNo = value; }

        }

    }

}

Step 3

After, doing it, I want to use of all the above declared properties , you store the many no. of students records, and do  some operation on these stored student records in the properties
like:

1- I want to select the records of that student which have "3" Roll No.

2- I want to select the records of that student which have "Any thing" Name.
and many more things.
 
So I think, at this time many more things are coming  in your mind, I can do this  one way or another way. But all the ways to solve the above problems taking line of code and it may be your code complexity will be increase.
So I discussed previously, Linq  query "800" times faster than the general query.  and to solve all the above problem with the help of Linq taking less time and less complexity and manage with easy code.


Step 1: 

File-New->Windows Form( write name of it)->ok and add the above class library (student.cs).

Step 2:

On  Form Load

       private void Form1_Load(object sender, EventArgs e)

        {

            stuar.Add(new Class1() { StuName = "Prince", StuRollNo = 1, StuAge = 22 });

            stuar.Add(new Class1() { StuName = "Arvind", StuRollNo = 2, StuAge = 22 });

            stuar.Add(new Class1() { StuName = "Sharad", StuRollNo = 3, StuAge = 24 });

            stuar.Add(new Class1() { StuName = "Pramod", StuRollNo = 4, StuAge = 25 });

            stuar.Add(new Class1() { StuName = "Dinesh", StuRollNo = 5, StuAge = 23 });

            stuar.Add(new Class1() { StuName = "Ravi", StuRollNo = 6, StuAge = 25 });

            stuar.Add(new Class1() { StuName = "Sachin", StuRollNo = 7, StuAge = 23 });

        }
 

General Experssion

Ques->I want to select the records of that student which have "5" Roll No.

Here OfType() is used For the element on the specified Type.

var res = from sturecords in stuar.OfType<Class1>() where (sturecords.StuRollNo == 5) select (sturecords);

            foreach (Class1 stures in res)

            {

                MessageBox.Show("Roll No: " + stures.StuRollNo + Environment.NewLine + "Name: " + stures.StuName + Environment.NewLine + "Age :" + stures.StuAge);

            }

Output1:

Lambda Expression

Ques->I want to select the records of that students which have  grater than "6" Roll No.

Ans:

var res = stuar.OfType<Class1>().Where(sturecords => sturecords.StuRollNo > 6).Select(sturecords => sturecords);

            foreach (Class1 stures in res)

            {

                MessageBox.Show("Roll No: " + stures.StuRollNo + Environment.NewLine + "Name: " + stures.StuName + Environment.NewLine + "Age :" + stures.StuAge);

            }

 Output2:

Anonymous Method

Ques->I want to select the records of that students which have  grater than "5" Roll No.

Ans:  In it, I create three anonymous methods, one for where condition (whe), second for orderby caluse (ord)  and last one for select statement ( sel).

Func<Class1, bool> whe = delegate(Class1 obj)

        {

            return obj.StuRollNo > 5;

        };

        Func<Class1, int> ord = delegate(Class1 obj)

        {

            return (Int32)obj.StuRollNo;

        };

        Func<Class1, Class1> sel = delegate(Class1 obj)

        {

            return obj;

        };

        private void button3_Click(object sender, EventArgs e)

        {

            var res = stuar.OfType<Class1>().Where(whe).OrderBy(ord).Select(sel);

            foreach (Class1 stures in res)

            {

                MessageBox.Show("Roll No: " + stures.StuRollNo + Environment.NewLine + "Name: " + stures.StuName + Environment.NewLine + "Age :" + stures.StuAge);

            }

        }

Output:3

 

Full Code:

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Collections;

namespace WindowsFormsApplication1

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        ArrayList stuar= new ArrayList();

        private void Form1_Load(object sender, EventArgs e)

        {

            stuar.Add(new Class1() { StuName = "Prince", StuRollNo = 1, StuAge = 22 });

            stuar.Add(new Class1() { StuName = "Arvind", StuRollNo = 2, StuAge = 22 });

            stuar.Add(new Class1() { StuName = "Sharad", StuRollNo = 3, StuAge = 24 });

            stuar.Add(new Class1() { StuName = "Pramod", StuRollNo = 4, StuAge = 25 });

            stuar.Add(new Class1() { StuName = "Dinesh", StuRollNo = 5, StuAge = 23 });

            stuar.Add(new Class1() { StuName = "Sachin", StuRollNo = 7, StuAge = 23 });

            stuar.Add(new Class1() { StuName = "Ravi", StuRollNo = 6, StuAge = 25 });

          

        }

        private void button1_Click(object sender, EventArgs e)

        {

            var res = from sturecords in stuar.OfType<Class1>() where (sturecords.StuRollNo == 5) select (sturecords);

            foreach (Class1 stures in res)

            {

                MessageBox.Show("Roll No: " + stures.StuRollNo + Environment.NewLine + "Name: " + stures.StuName + Environment.NewLine + "Age :" + stures.StuAge);

            }

        }

        private void button2_Click(object sender, EventArgs e)

        {

            var res = stuar.OfType<Class1>().Where(sturecords => sturecords.StuRollNo > 6).Select(sturecords => sturecords);

            foreach (Class1 stures in res)

            {

                MessageBox.Show("Roll No: " + stures.StuRollNo + Environment.NewLine + "Name: " + stures.StuName + Environment.NewLine + "Age :" + stures.StuAge);

            }

        }

        Func<Class1, bool> whe = delegate(Class1 obj)

        {

            return obj.StuRollNo > 5;

        };

        Func<Class1, int> ord = delegate(Class1 obj)

        {

            return (Int32)obj.StuRollNo;

        };

        Func<Class1, Class1> sel = delegate(Class1 obj)

        {

            return obj;

        };

        private void button3_Click(object sender, EventArgs e)

        {

            var res = stuar.OfType<Class1>().Where(whe).OrderBy(ord).Select(sel);

            foreach (Class1 stures in res)

            {

                MessageBox.Show("Roll No: " + stures.StuRollNo + Environment.NewLine + "Name: " + stures.StuName + Environment.NewLine + "Age :" + stures.StuAge);

            }

        }

    }

}

Now I am taking about Group by, Count, and Joining with the help of Property and Linq.

Suppose, You create two different classes , one for "employee" and other is "department", Lets suppose "employee" class contain "empcode", "empname", "deptcode" as properties. and department class contain "depname", "depcode", "loc" as properties.

Then think, if we design same thing in sql as a database table, then how's structure look like:

Emp Table

EmpCode	EmpName	DeptCode
1	Satya	101
2	Sharad	101
3	Ravi	102
4	Mohit	103
5	Rohit	104
6	Pramod	104

Dept Table

DeptName	DepCode	Loc
IT	101	New Delhi
IT	101	New Delhi
Account	102	Delhi
Hr	103	Gurgaon
Clerk	104	Noida
Clerk	104	Noida

And You want to count "total no of department", "recorders  by group by" , "Joining". with the help of above tables. So in database you follow the joining concept. Here I do the same thing with the help of Properties and Linq.

Create  class For Emp( emp.cs)

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace WindowsFormsApplication2

{

    class emp

    {

        public int EmpCode { get; set; }

        public string EmpName { get; set; }

        public int DeptName { get; set; }

    }

}

Create a Windows Form and add ref of emp.cs

Ques- Count Total no of dept with group by

Ans

var res = emps.OfType<emp>().GroupBy(enpsres => enpsres.DeptCode);

            foreach (var s in res)

            {

                MessageBox.Show("Dept Code ="+s.Key.ToString()+" Total Count= "+s.Count<emp>().ToString());

            }

 Output4:

Full Code:

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Collections;

namespace WindowsFormsApplication2

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        ArrayList emps= new ArrayList();

        private void Form1_Load(object sender, EventArgs e)

        {

            emps.Add(new emp() {EmpCode=1, EmpName="Satya",DeptCode=101 });

            emps.Add(new emp() { EmpCode = 2, EmpName = "Sharad", DeptCode = 101 });

            emps.Add(new emp() { EmpCode = 3, EmpName = "Ravi", DeptCode = 102 });

            emps.Add(new emp() { EmpCode = 4, EmpName = "Mohit", DeptCode = 103 });

            emps.Add(new emp() { EmpCode = 5, EmpName = "Rohit", DeptCode = 104 });

            emps.Add(new emp() { EmpCode = 6, EmpName = "Pramod", DeptCode = 104 });

        }

        private void button1_Click(object sender, EventArgs e)

        {

            var res = emps.OfType<emp>().GroupBy(enpsres => enpsres.DeptCode);

            foreach (var s in res)

            {

                MessageBox.Show("Dept Code ="+s.Key.ToString()+" Total Count= "+s.Count<emp>().ToString());

            }

        }

    }

}

Create another  class For dept( dept.cs)

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace WindowsFormsApplication2

{

    class dept

    {

        public string DeptName { get; set; }

        public int DepCode { get; set; }

        public string Loc { get; set; }

    }

}

Ques- Findout Empcode, EmpName , DeptName and Loc.

Ans: So, doing all these thing you need the joining because both properties class are different.

var res = from empsres in emps.OfType<emp>() join deptres in deps.OfType<dept>() on empsres.DeptCode equals deptres.DepCode

                      select (new { empsres.EmpCode, empsres.EmpName, deptres.DeptName, deptres.Loc });

            foreach (var s in res)

            {

                MessageBox.Show("EmpCode: "+s.EmpCode+Environment.NewLine+" EmpName="+s.EmpName+Environment.NewLine+

                    "DeptName: "+s.DeptName+Environment.NewLine+"Location="+s.Loc +"");

            }

  Output5:

Fullcode (Add the ref of "emp.cs" and "dept.cs" in windows form)

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Collections;

namespace WindowsFormsApplication2

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        ArrayList emps= new ArrayList();

        ArrayList deps = new ArrayList();

        private void Form1_Load(object sender, EventArgs e)

        {

            emps.Add(new emp() {EmpCode=1, EmpName="Satya",DeptCode=101 });

            emps.Add(new emp() { EmpCode = 2, EmpName = "Sharad", DeptCode = 101 });

            emps.Add(new emp() { EmpCode = 3, EmpName = "Ravi", DeptCode = 102 });

            emps.Add(new emp() { EmpCode = 4, EmpName = "Mohit", DeptCode = 103 });

            emps.Add(new emp() { EmpCode = 5, EmpName = "Rohit", DeptCode = 104 });

            emps.Add(new emp() { EmpCode = 6, EmpName = "Pramod", DeptCode = 104 });

            deps.Add(new dept() {DeptName="IT",DepCode=101,Loc="New Delhi"  });

            deps.Add(new dept() { DeptName = "IT", DepCode = 101, Loc = "New Delhi" });

            deps.Add(new dept() { DeptName = "Account", DepCode = 102, Loc = "Delhi" });

            deps.Add(new dept() { DeptName = "Hr", DepCode = 103, Loc = "Gurgaon" });

            deps.Add(new dept() { DeptName = "Clerk", DepCode = 104, Loc = "Noida" });

            deps.Add(new dept() { DeptName = "Clerk", DepCode = 104, Loc = "Noida" });

        }

        private void button1_Click(object sender, EventArgs e)

        {

            var res = emps.OfType<emp>().GroupBy(enpsres => enpsres.DeptCode);

            foreach (var s in res)

            {

                MessageBox.Show("Dept Code ="+s.Key.ToString()+" Total Count= "+s.Count<emp>().ToString());

            }

        }

        private void button2_Click(object sender, EventArgs e)

        {

            var res = from empsres in emps.OfType<emp>() join deptres in deps.OfType<dept>() on empsres.DeptCode equals deptres.DepCode

                      select (new { empsres.EmpCode, empsres.EmpName, deptres.DeptName, deptres.Loc });

            foreach (var s in res)

            {

                MessageBox.Show("EmpCode: "+s.EmpCode+Environment.NewLine+" EmpName="+s.EmpName+Environment.NewLine+

                    "DeptName: "+s.DeptName+Environment.NewLine+"Location="+s.Loc +"");

            }

        }

     

    }

}

In next article I will discuss about Linq and SQL.