@Atif Try below function to convert time to 100 format.
protected double ConvertTo100(string strTemp)
{
strTemp = strTemp.Replace(':', '.');
double dblTemp;
dblTemp = Convert.ToDouble(strTemp);
double dblHH = Math.Floor(dblTemp);
double dblMM = Math.Round(dblTemp - Math.Floor(dblTemp), 2) * 60 / 100;
double dboReturn;
dboReturn = dblHH + dblMM;
return dboReturn;
}
than you can use this funcation like..
DGTotalMoney.DigitText = Convert.ToString(ConvertTo100("Your time here in HH:MM format") * (double.Parse("Your Price Here")));