how to uncheck the radio button

I suggest you evaluate whether CheckBoxes meet your needs in this design scenario.

RadioButtons are meant to be used in groups ... for example, all the RadioButtons in a WinForms Panel are a "group" ... where one of them will always have its CheckState Property set to 'Checked.

By designing your user-interface using the Microsoft Windows User Interface Guidelines, you will presenting users with interactive they are familiar with. Here's guidelines for RadioButtons: [^].

In WinForms it is, perhaps, an inconsistent behavior that a bunch of RadioButtons put in some ContainerControl, or on a Form, initially appear at design-time, and then at run-time, as all unchecked unless you have at design-time set the checked property of one of them.

hello

bool isChecked =false;
    private void radioButton1_CheckedChanged(object sender, EventArgs e)
    {
        isChecked = radioButton1.Checked;
    }

    private void radioButton1_Click(object sender, EventArgs e)
    {
        if (radioButton1.Checked && !isChecked)
            radioButton1.Checked = false;
        else
        {
            radioButton1.Checked = true;
            isChecked = false;
        }
    }