Hi Nainika,
Check these values:
dr["Description"] = cmbService.SelectedValue;
dr["Duration"] = txtDuration.Text;
dr["Price"] = txtPrice.Text;
cmbService will have only one selected value. Check what text you have in these two TextBoxes. I guess the values that you are assigning will remain the same.
Apply a debugger and check them first.
Regards,
Praneet