Assign the same following CheckChanged event to all CheckBoxes
private void CheckBox_Changed(object sender, EventArgs e)
{
if ((sender as CheckBox).Checked)
{
foreach (CheckBox c in groupBox1.Controls.OfType<CheckBox>())
{
if (c != (sender as CheckBox))
{
c.Checked = false;
}
}
}
}
And you must have the following namespace inherited
using System.Linq;