I could swear someone posted this same question to the C# group recently.

You will have to handle the Click event. If they are setting it from
unchecked to
checked, you will have to uncheck all the other ones. If they are setting
it from
checked to unchecked, you will have to make it ignore it.

Robin S.

Hi Michael,

You're right that we could handle the Click event of the CheckBox controls
to check just one CheckBox.

The following is a sample. It requires that a GroupBox is added on the form
and 3 CheckBox added into the GroupBox.

public Form1()
{
        this.checkBox1.Click += new EventHandler(checkBox_Click);
        this.checkBox2.Click += new EventHandler(checkBox_Click);
        this.checkBox3.Click += new EventHandler(checkBox_Click);
}
void checkBox_Click(object sender, EventArgs e)
{
        CheckBox control = sender as CheckBox;

           if (control != null)
           {
               foreach (CheckBox ckb in this.groupBox1.Controls)
               {
                   ckb.Checked = false;
               }
               control.Checked = true;
           }
 }

Hope this helps.
If you have any question, please feel free to let me know.

Sincerely,
Linda Liu
Microsoft Online Community Support

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Others have answered your question, but why would you do that? Users
will find it confusing. Check boxes are supposed to be for "select
zero, one or more" and radio buttons (or combos) are for "select one
only". That's why there are different controls in Windows in the first
place. It's generally a bad idea to subvert the normal GUI
conventions.

--
Philip Daniels