DataGridView is a type of toolbox that can show data from database table. Here I am going to discuss about dataGridView. 

In my previous post, I had already discussed about insert,upadate and delete data in a database table.In that post I uesd a window.Now I am just adding a dataGridView toolbox in that window and going to discuss about showing tables in that dataGridView .
After adding dataGridView,  the window will becomes like this,


Now add the following code in Gateway.cs Class ,
  
public static List<StudentMark> GetStudent()
{
 string connectionString = @"Here write our own Data Source";
 SqlConnection connection = new SqlConnection(connectionString);
 connection.Open();

 string query = @"select * from t_Mark";
 SqlCommand command = new SqlCommand(query, connection);
 SqlDataReader reader = command.ExecuteReader();

 List<StudentMark> studentList = new List<StudentMark>();

 while (reader.Read())
 {
  StudentMark studentObj = new StudentMark()
                                             {
                                                 StudentRoll = reader[0].ToString(),
                                                 Bangla = reader[1].ToString(),
                                                 English = reader[2].ToString(),
                                                 Math = reader[3].ToString()
                                             };

  studentList.Add(studentObj);
 }
 return studentList;
 }
}

Now double click on SHOW BUTTON :

private void showButton_Click(object sender, EventArgs e)
{
 List<StudentMark> studentList = Gateway.GetStudent();

 dataGridView1.AutoGenerateColumns = true;
 dataGridView1.DataSource = studentList;
}

Now if we insert,update or delete any information in a database table and click on SHOW BUTTON then we can see the information in dataGridView box from database.I give an example here,