How to create month columns in database basedon no.of months

Question

i have

No of months

Start date

end date  in my page

 

when i give number of months 3 and start date 10/7/2015 then end date will calculated to 10/9/2015 automatically.

 

And now i want to create extra columns in database i.e June-2015, july and august
in this table or another table 

 

how to create month columns automatically based on Number months and start date,end date  

 

 

my code is 

 

protected void Button1_Click(object sender, EventArgs e)

{

SqlCommand cmd = new SqlCommand("Insert into monthcal (NoOfMonths,StartDate,EndDate) values (@NoOfMonths,@StartDate,@EndDate)", con);

cmd.Parameters.AddWithValue("@NoOfMonths", txtNoOfMonths.Text.ToString());

cmd.Parameters.AddWithValue("@StartDate", txtStartDate.Text.ToString());

cmd.Parameters.AddWithValue("@EndDate", txtEndDate.Text.ToString());

con.Open();

cmd.ExecuteNonQuery();

}

 

protected void txtStartDate_TextChanged(object sender, EventArgs e)

{

string inputString = txtStartDate.Text;

DateTime dt = DateTime.ParseExact(inputString, "yyyy/MM/dd", CultureInfo.InvariantCulture);

dt = dt.AddMonths(Convert.ToInt32(txtNoOfMonths.Text));

txtEndDate.Text = dt.ToString("yyyy/MM/dd");

DateTime Date1 = Convert.ToDateTime(txtStartDate.Text);

DateTime Date2 = Convert.ToDateTime(txtEndDate.Text);

//int Datediff = ((Date2.Year - Date1.Year) * 12) + Date1.Month - Date2.Month;

int DayDiff = (Date2.Date - Date1.Date).Days;

Label1.Text = "Total days" + " " + (DayDiff.ToString());