Refer below link.

how to use thousand seprator for label

ok I know it but that code was different here I want label dispalay numer from database and codes are different:

link codes was:

int total = Convert.ToInt32(totalPrice);
lbltotal.Text = total.ToString("N0"); //1,000,000,000
lbltotal.Text = total.ToString("N"); //1,000,000,000.00

but here is:

LblkolP.Text = toPersianNumber(_dr["TotalPrice"].ToString("N0"));

bind from database and display in label

First you need to convert the value to int or decimal and then convert to ToString with argument.

LblkolP.Text = toPersianNumber(Convert.ToInt32(_dr["TotalPrice"]).ToString("N0"));