อธิบายโค้ด1บรรทัด ให้อ่านหน่อยคะ DataGridViewCheckBoxCell = DirectCast(DataGridView1.CurrentCell, DataGridViewCheckBoxCell)

Dim chk As DataGridViewCheckBoxCell = DirectCast(DataGridView1.CurrentCell, DataGridViewCheckBoxCell)

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;

namespace MyDataGridView
{
    public partial class Form1 : Form
    {
        private System.Data.DataTable DtSource;
        private System.Data.DataTable DtTemp;

        private System.Windows.Forms.DataGridView dataGridView1;

        private System.Windows.Forms.Button editButton;
        private System.Windows.Forms.Button saveButton;
        private System.Windows.Forms.Button cancelButton;

        public Form1()
        {
            InitializeComponent();

            this.DtSource = new System.Data.DataTable();
            this.DtTemp = new System.Data.DataTable();

            this.dataGridView1 = new System.Windows.Forms.DataGridView();

            this.editButton = new System.Windows.Forms.Button();
            this.cancelButton = new System.Windows.Forms.Button();
            this.saveButton = new System.Windows.Forms.Button();

            // 
            // dataGridView1
            // 
            this.dataGridView1.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
            this.dataGridView1.Location = new System.Drawing.Point(12, 12);
            this.dataGridView1.Name = "dataGridView1";
            this.dataGridView1.Size = new System.Drawing.Size(268, 208);
            this.dataGridView1.TabIndex = 0;
            // 
            // editButton
            // 
            this.editButton.Location = new System.Drawing.Point(205, 231);
            this.editButton.Name = "editButton";
            this.editButton.Size = new System.Drawing.Size(75, 23);
            this.editButton.TabIndex = 1;
            this.editButton.Text = "Edit";
            this.editButton.UseVisualStyleBackColor = true;
            this.editButton.Click += new System.EventHandler(this.editButton_Click);
            // 
            // SaveButton
            // 
            this.saveButton.Location = new System.Drawing.Point(123, 231);
            this.saveButton.Name = "SaveButton";
            this.saveButton.Size = new System.Drawing.Size(75, 23);
            this.saveButton.TabIndex = 1;
            this.saveButton.Text = "Save";
            this.saveButton.UseVisualStyleBackColor = true;
            this.saveButton.Hide();
            this.saveButton.Click += new EventHandler(saveButton_Click);
            // 
            // CancelButton
            // 
            this.cancelButton.Location = new System.Drawing.Point(204, 231);
            this.cancelButton.Name = "CancelButton";
            this.cancelButton.Size = new System.Drawing.Size(75, 23);
            this.cancelButton.TabIndex = 2;
            this.cancelButton.Text = "Cancel";
            this.cancelButton.UseVisualStyleBackColor = true;
            this.cancelButton.Hide();
            this.cancelButton.Click += new EventHandler(cancelButton_Click);

            this.Controls.Add(this.dataGridView1);
            this.Controls.Add(this.saveButton);
            this.Controls.Add(this.cancelButton);
            this.Controls.Add(this.editButton);

            DataGridViewCheckBoxColumn CheckBoxColumn = new DataGridViewCheckBoxColumn();
            CheckBoxColumn.ReadOnly = false;
            CheckBoxColumn.DisplayIndex = 0;
            CheckBoxColumn.DefaultCellStyle.BackColor = System.Drawing.Color.LightGray;
            CheckBoxColumn.TrueValue = true;
            CheckBoxColumn.FalseValue = false;
            CheckBoxColumn.Width = 20;

            DataGridViewTextBoxColumn IdColumn = new DataGridViewTextBoxColumn();
            IdColumn.ReadOnly = true;
            IdColumn.HeaderText = "ID";
            IdColumn.DefaultCellStyle.BackColor = System.Drawing.Color.LightGray; ;
            IdColumn.DataPropertyName = "ID";

            DataGridViewTextBoxColumn NameColumn = new DataGridViewTextBoxColumn();
            NameColumn.ReadOnly = true;
            NameColumn.HeaderText = "Name";
            NameColumn.DefaultCellStyle.BackColor = System.Drawing.Color.LightGray;
            NameColumn.DataPropertyName = "DayName"; 
            
            dataGridView1.AutoGenerateColumns = false;
            dataGridView1.AllowUserToAddRows = false;
            dataGridView1.AllowUserToDeleteRows = false;

            dataGridView1.Columns.Add(CheckBoxColumn);
            dataGridView1.Columns.Add(IdColumn);
            dataGridView1.Columns.Add(NameColumn);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            DtSource = GetInitialData();
            dataGridView1.DataSource = DtSource.Copy();
        }

        private DataTable GetInitialData()
        {
            string[] DayArray = new string[] { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };
            int Count = 0;

            DataTable Dt = new DataTable("DayTable");
            Dt.Columns.Add(new DataColumn("ID", System.Type.GetType("System.Int16")));
            Dt.Columns.Add(new DataColumn("DayName", System.Type.GetType("System.String")));

            foreach (string aDay in DayArray)
            {
                DataRow Dr = Dt.NewRow();
                Dr["ID"] = ++Count;
                Dr["DayName"] = aDay;
                Dt.Rows.Add(Dr);
            }

            return Dt;
        }

        private void editButton_Click(object sender, EventArgs e)
        {
            int isCheck = 0;

            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                if (Convert.ToBoolean(row.Cells[0].Value) == true)
                {
                    row.Cells[0].Style.BackColor = System.Drawing.Color.White;
                    row.Cells[1].Style.BackColor = System.Drawing.Color.White;
                    row.Cells[2].Style.BackColor = System.Drawing.Color.White;

                    row.Cells[1].ReadOnly = false;
                    row.Cells[2].ReadOnly = false;
                    isCheck++;
                }

                row.Cells[0].ReadOnly = true;
            }

            if (isCheck > 0)
            {
                DtTemp = (dataGridView1.DataSource as DataTable).Copy();

                editButton.Hide();
                saveButton.Show();
                cancelButton.Show();
            }
        }

        private void saveButton_Click(object sender, EventArgs e)
        { 
            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                if (Convert.ToBoolean(row.Cells[0].Value) == true)
                {
                    row.Cells[0].Style.BackColor = System.Drawing.Color.LightGray;
                    row.Cells[1].Style.BackColor = System.Drawing.Color.LightGray;
                    row.Cells[2].Style.BackColor = System.Drawing.Color.LightGray;
                }

                row.Cells[0].Value = false;
                while (row.Cells[1].ReadOnly == false) row.Cells[1].ReadOnly = true;
                while (row.Cells[2].ReadOnly == false) row.Cells[2].ReadOnly = true;
            }

            DtSource = (dataGridView1.DataSource as DataTable).Copy();

            editButton.Show();
            saveButton.Hide();
            cancelButton.Hide();
        }

        private void cancelButton_Click(object sender, EventArgs e)
        {
            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                if (Convert.ToBoolean(row.Cells[0].Value) == true)
                {
                    row.Cells[0].Style.BackColor = System.Drawing.Color.LightGray;
                    row.Cells[1].Style.BackColor = System.Drawing.Color.LightGray;
                    row.Cells[2].Style.BackColor = System.Drawing.Color.LightGray;
                }

                row.Cells[0].Value = false;
                while (row.Cells[1].ReadOnly == false) row.Cells[1].ReadOnly = true;
                while (row.Cells[2].ReadOnly == false) row.Cells[2].ReadOnly = true;
            }

            dataGridView1.DataSource = DtTemp.Copy();

            editButton.Show();
            saveButton.Hide();
            cancelButton.Hide();
        }
    }
}

 For i As Integer = 1 To DataGridView1.Rows.Count - 1
            Dim chk As DataGridViewCheckBoxCell = boolean(DataGridView1.Rows(i), DataGridViewCheckBoxCell)
            If chk.Value = True Then
                Dim update As String = "update bcapinvoicesub set groupcode='" & DataGridView1.CurrentRow.Cells("รหัสกรุ๊ป1").Value.ToString() & "' where itemcode='" & DataGridView1.CurrentRow.Cells("รหัสสินค้า").Value.ToString() & "'"
                Dim Cmd = New SqlCommand(update, connString)
                Cmd.ExecuteNonQuery()
                Dim update1 As String = "update bcitem set groupcode='" & DataGridView1.CurrentRow.Cells("รหัสกรุ๊ป2").Value.ToString() & "' where code='" & DataGridView1.CurrentRow.Cells("รหัสสินค้า").Value.ToString() & "'"
                Dim Cmd1 = New SqlCommand(update1, connString)
                Cmd1.ExecuteNonQuery()
                MsgBox("เรียบร้อย", MsgBoxStyle.OkOnly, "ผลการอัพเดต")
            End If
   Next i