C#

List<RadioButton> List2 = new List<RadioButton>();
List<RadioButton> List1 = new List<RadioButton>();

            //Add a dummy value to first index
            List1.Add(0,null);
            List1.Add(1,RadioButton1);
            List1.Add(2,RadioButton2);
            List1.Add(3,RadioButton3);
            List1.Add(4,RadioButton4);

//Generate random List index 
int listIndex = RandNum.Next(1, 4);

int i=1;
while(i<List1.Count)
{
//Check if the radiobutton at index of Listindex in List1 is in List2
 if (!List2.Contains(List1(listIndex )))
     {
       //If radiobutton did not exist in List2, add it to List2
       List2.Add(List1(listIndex ));                               
       i++;
     }
}

private void button1_Click(object sender, EventArgs e)
        {
Excel.Application exapp=null;
            Excel.Workbook exbook=null;
            Excel.Worksheet exsheet = null;
            object misvalue = System.Reflection.Missing.Value;
            exapp = new Excel.Application();
            exapp.SheetsInNewWorkbook = 1;
            exbook = exapp.Workbooks.Add(misvalue);
            exsheet = (Excel.Worksheet)exbook.Worksheets.get_Item(1);
            exsheet.Cells[1, 1] = "First Name";
            exsheet.Cells[1, 2] = "Last Name";
            exsheet.Cells[1, 3] = "Address1";
            exsheet.Cells[1, 4] = "Address2";
            exsheet.Cells[1, 5] = "City";
            exsheet.Cells[1, 6] = "PinCode";
            exsheet.Cells[1, 7] = "Phone Number";
            exsheet.Cells[2, 1] = textBox1.Text.ToString();
            exsheet.Cells[2, 2] = textBox2.Text.ToString();
            exsheet.Cells[2, 3] = textBox3.Text.ToString();
            exsheet.Cells[2, 4] = textBox4.Text.ToString();
            exsheet.Cells[2, 5] = textBox5.Text.ToString();
            exsheet.Cells[2, 6] = textBox6.Text.ToString();
            exsheet.Cells[2, 7] = textBox7.Text.ToString();
            exbook.SaveAs("rep.xls", Excel.XlFileFormat.xlWorkbookNormal, misvalue, misvalue, misvalue, misvalue, Excel.XlSaveAsAccessMode.xlExclusive, misvalue, misvalue, misvalue, misvalue, misvalue);
            exapp.Quit();
            releaseObject(exapp);
            releaseObject(exbook);
            releaseObject(exsheet);
            }