C# winform checkbox still checked

In a button click function, I set checkbox.check = false; but when I click button again, checkbox still in checked

here is my code:

// Header全選加上CheckBox
System.Drawing.Rectangle rect = dataGridView1.GetCellDisplayRectangle(0, -1, true);
rect.X = rect.Location.X + rect.Width / 4 - 9;
rect.Y = rect.Location.Y + (rect.Height / 2 - 9);
SolidBrush solidBrush = new SolidBrush(Color.White);
System.Windows.Forms.CheckBox checkBox = new System.Windows.Forms.CheckBox();
checkBox.Name = "checkBoxHeader";
checkBox.Size = new Size(18, 18);
checkBox.Location = rect.Location;
//checkBox.AutoCheck = false;
//MessageBox.Show(checkBox.Checked.ToString());
checkBox.Checked = false;
checkBox.Invalidate();
checkBox.Update();
dataGridView1.RefreshEdit();
checkBox.CheckedChanged += new EventHandler(checkBox_CheckedChanged);
dataGridView1.Controls.Add(checkBox);

I set MessageBox to show checkbox value, but the value is "False"

How can I set checkbox is unchecked when I click botton?

Thanks a lot