C# WinApp CheckBox ไม่มีเครื่องหมายถูกให้ เมื่อ CheckBox.Checked = true ครับ

 void CheckResult()
        {
            if (Convert.ToDouble(readingTextBox.Text) == 0.0 || 
                Convert.ToDouble(uncertaintyTextBox.Text) == 0.0
                || minV == 0 || maxV == 0) return;

             _c = Convert.ToDouble(readingTextBox.Text);
             _t = Convert.ToDouble(uncertaintyTextBox.Text);

             minR = _c - _t;  maxR = _c + _t;
           
            resultCheckBox.Checked =!(minR < minV || maxR > maxV);
           
           this.manEditTextBox.Text = dllExtension.UserLogin.EmployeeName;

            this.dateEditDateTimePicker.Value = DateTime.Now;
        }

private void cal_DateDateTimePicker_ValueChanged(object sender, EventArgs e)
        {
            nextCal_DateDateTimePicker.Value = cal_DateDateTimePicker.Value.AddYears(3);
        }