Events On Collection (List) In C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ListCollection
{
    internal class Student
    {
        //Properties of Student
        public int RollNumber { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
        public string City { get; set; }
    }
}

Now we Add Event on Show In Grid Button

• Double Click on Show In Grid Button and add this code
• btnShowInGrid_Click() is an Event for Load Data in GridView Using LoadData() Method.
• dataGridView1.DataSource is a property to get Source in DataGridView, we assign students List as DataSource.

  private void btnShowInGrid_Click(object sender, EventArgs e) {
      LoadData();
  }
  private void LoadData() //this will load List Data in DataGridView
  {
      dataGridView1.DataSource = null;
      dataGridView1.DataSource = students; //data Source is students list
  }

  Now run your Code, Enter Values -> Click on Save -> Click on Show In Grid. You can see your List values in Grid.

Create Button Controls for First, Last, Previous and Next

• To view Lists First, Last, Previous and Next Values Add 4 Button Controls, Right Click -> Properties on each.
• Change their Text as First, Previous, Next, Last.
• Change their Name as btnFirst, btnPrevious, btnNext, btnLast.

Figure 8

Now we Add Event on First, Previous, Next, Last Button

For Getting Student Index value create GetStudentAtIndex(..){...} Method, it Gets index of students List and Compare each Row of DataGridView and highlights Row where the index value is matched.

private void GetStudentAtIndex(int index)
{
    foreach (DataGridViewRow row in dataGridView1.Rows)
    {
        if (Convert.ToInt32(row.Cells[0].RowIndex) == index)
        {
            // This Code Highlights Row in Grid
            row.DefaultCellStyle.BackColor = Color.LightBlue; 
        }
    }
}

Add this code before List<Students>….. Creation line to access index value for all these control.

int index = 0;    //index value for Grid View
//Creating a List Collection for Student Class
List<Student> students = new List<Student>();

Double Click on First Button and Add this code, here we pass 0 as First index of List.

private void btnFirst_Click(object sender, EventArgs e)
{  
    index = 0;
    LoadData();
    GetStudentAtIndex(0);
}

Now run your Code, Enter Values -> Click on Save -> Click on Show In Grid, Click on First Button. You can see first value of Grid is Highlighted.

Double Click on Last Button and Add this code, here we pass Last index of List.

private void btnLast_Click(object sender, EventArgs e)
{
    index = students.Count - 1;
    LoadData();
    GetStudentAtIndex(students.Count - 1);
} 

Now run your Code, Enter Values -> Click on Save -> Click on Show In Grid, Click on Last Button. You can see last value of Grid is Highlighted.

Double Click on Previous Button and Add this code, here we pass index after 0

private void btnPrevious_Click(object sender, EventArgs e)
{
    if (index > 0)
    {
        index -= 1;
        LoadData();
        GetStudentAtIndex(index);
    }
}

Now run your Code, Enter Values -> Click on Save -> Click on Show In Grid, Click on Previous Button. You can see Previous value of Grid is Highlighted on each click if index is less than first position.

Double click on Next Button and add this code, here we pass index before Last value of List.

private void btnNext_Click(object sender, EventArgs e)
{
    if (index < students.Count - 1)
    {
        index += 1;
        LoadData();
        GetStudentAtIndex(index);
    }
}

Now run your Code, Enter Values -> Click on Save -> Click on Show In Grid, Click on Next Button. You can see Next value of Grid is Highlighted on each click if index is less than Last position. 

Create Button Control for Find

• Add a label, Right Click -> Properties Text - Find By RollNumber.
• Add a TextBox to give RollNumber to Find, Right Click -> Properties Name - txtFind.
• Add Button, Right Click -> Properties Text - Find and Name - btnFind.

Figure 9

Now we Add Event on Find Button

Double click on Find Button and add this code.

In btnFind_Click Event here we assign rollNumber in a variable to find, and use foreach loop to compare it with all rollNumber values in List.

private void btnFind_Click(object sender, EventArgs e)
{
    LoadData();
    int rollNumber = Convert.ToInt32(txtFind.Text);

    foreach (DataGridViewRow row in dataGridView1.Rows)
    {
        if (Convert.ToInt32(row.Cells[0].Value) == rollNumber)
        {
            row.DefaultCellStyle.BackColor = Color.LightBlue;
        }
    } 
}

Now run your code, Enter Some Values -> Click on Save ->Enter any of the RollNumber value in Find By RollNumber TextBox that you stored in the List, click on Find, it will navigate to the Found value in the Grid.

Create Button Control for Update

• Add a Button Control, Right Click -> Properties Text - Update and Name - btnUpdate.

Figure 10

Now we Add Event on Update Button

• Double Click on Update Button and add this Code
• In btnUpdate_Click Event we Find the Same RollNumber value of TextBox in the students List.

If the value is found then we put values of textBoxs in Properties of that student object.

private void btnUpdate_Click(object sender, EventArgs e)
{
    int rollNumber = Convert.ToInt32(txtRollNumber.Text);
  //here we compare each rollnumbar of list with the textRollNumber value
    foreach (Student student in students)
    {
        if (student.RollNumber == rollNumber)
        {
            try
            {
                student.RollNumber = Convert.ToInt32(txtRollNumber.Text);
                student.Name = txtName.Text;
                student.Age = Convert.ToInt32(txtAge.Text);
                student.City = txtCity.Text;
                SetStatus("Data Updated Successfully !!", false);
                LoadData();
            }
            catch (Exception ex)
            {
                SetStatus(ex.Message, true);
            }
        }
    }
}

Now run your code enter some student detail Save it, show them in Grid with Show In Grid Button and enter one more detail of student but make sure to give RollNumber that you give to existing student and fill other details.

Click on Update Button this time, not on Save you can see once you click, values go change and Load in the GridView.

Create Button Control For Delete

Add a Button Control, Right Click -> Properties Text - Delete and Name - btnDelete.

Figure 11

Now we Add Event on Delete Button

• Double Click on Delete Button and add this code
• In btnDelete_Click Event we compare RollNumber value of TeatBox with RollNumber value in the List.

If the value found then we remove that value from the List using Remove() Method.

private void btnDelete_Click(object sender, EventArgs e)
{
    int rollNumber = Convert.ToInt32(txtFind.Text);
    foreach (Student student in students)
    {
        if (student.RollNumber == rollNumber)
        {
            try
            {
                students.Remove(student);
                LoadData();
                SetStatus("Data Deleted Successfully !!", false);
            }
            catch (Exception ex)
            {
                SetStatus(ex.Message, true);
            }
            break;
        }
    }
}

Now run your application enter Some Students Details Click on Save each time -> Click on Show In Grid to view students List values in Grid.

Now enter one of existing student RollNumber in Find By RollNumber TextBox -> Click on Delete Button.

You can see value of that student is Now deleted from List students.

Application is Now completed, you learned how to add Events on Collection (List) in C#.

Summary

List is a collection used for dynamic memory allocation as you see in ListCollection Application above. You can access List values using index. In List Collection we can store, find, update, Delete and perform other functionalities. You can also show DataGridView Control to show List values at Run time even you can use other Controls also like MessageBox as per your need. In Generic type of List we can use various type of data.