how to i increment months in c# windows application

private void btnPay_Click(object sender, EventArgs e)

{

_repayLoan.AccountNo = PaymentGatewayForm.SetValueForText1;

_repayLoan.LoanId = Convert.ToInt32(PaymentGatewayForm.SetValueForText2);

_loanamt = Convert.ToDecimal(PaymentGatewayForm.SetValueForText4);

_intrest = Convert.ToDecimal(PaymentGatewayForm.SetValueForText5);

decimal _monthlyintreast = Convert.ToDecimal(_intrest / 1200);

_montlypmt = Convert.ToDecimal(PaymentGatewayForm.SetValueForText6);

_totpmt = Convert.ToDecimal(PaymentGatewayForm.SetValueForText7);

_repayLoan.LoanType = PaymentGatewayForm.SetValueForText8;

_year = (PaymentGatewayForm.SetValueForText9);

_date = PaymentGatewayForm.SetValueForText10;

_months = Convert.ToInt16(PaymentGatewayForm.SetValueForText12);

_repayamt = Convert.ToDecimal(txtRepayamt.Text);

string temp = PaymentGatewayForm.SetValueForText1;

var user = (from iteam in _dbEntity.LoanDetailTables

where iteam.AccountNo == temp

select iteam).FirstOrDefault();

_monthlyrate=_intrest/12;

int a = Convert.ToInt16(_year);

_remaningMonths = _months;

if(_intrest>0)

{

if (_remaningMonths > 0)

{

_remaningMonths = Convert.ToInt16(user.RemaningMonths);

if (user.LoanAmount >= 0)

{

//newBalance = Convert.ToDecimal(user.LoanAmount - _repayamt);

//decimal payable = Convert.ToDecimal (user.LoanAmount / _remaningMonths);

newBalance = Convert.ToDecimal(user.LoanAmount - _repayamt);

user.LoanAmount = newBalance;

_remaningMonths--;

}

else

{

if(user.LoanAmount<0)

{

user.LoanAmount = 0;

MessageBox.Show("Your Loan payment has been closed");

user.LoanStatus = "Closed";

}

}

// here i am adding months

DateTime savedtime = Convert.ToDateTime(_date);

DateTime dt = savedtime.AddMonths(1);

// DateTime dt = DateTime.Now.AddMonths(1);

user.Date = Convert.ToString(dt);

user.RemaningMonths = _remaningMonths;

_repayLoan.AccountNo = user.AccountNo;

_repayLoan.LoanType = user.TypeOfLoan;

_repayLoan.LoanId = user.LoanId;

_repayLoan.RemaningLoanAmount = newBalance;

_repayLoan.ActualLoanAmount = _loanamt;

_repayLoan.Intrest = _intrest;

_repayLoan.LoanPeriod = Convert.ToString(_remaningMonths);

_repayLoan.MonthlyPayment = user.MonthlyPayment;

_repayLoan.Date = user.Date;

_repayLoan.TotalPayment = user.TotalPayment;

_repayLoan.RepayAmount = _repayamt;

_repayLoan.RemaningLoanAmount = newBalance;

_dbEntity.RepayLoanDetailTables.Add(_repayLoan);

_dbEntity.SaveChanges();

// listBox1.Items.Add(" Monthly Payment amount " + _montlypmt + " Payment Id " + Paymentno + " Intrest " + _intrest + "Loan amount " + _amounttowardsprinciple + " Monthyintrestcost" + _monthlyintrestcost + "balance " + newBalance);

}