I have a variable which is storing as decimal:
decimal firststYrComp = Int16.Parse(tb1stYr.Text.ToString());
Now I have this to get typecasted
You can use decimal's built in converter.
decimal decimalValue = 5;
double doubleValue = decimal.ToDouble(decimalValue);
Just Try
Decimal yourDecimal = 3.222222m;
Convert.ToDouble(yourDecimal);
You answered your own question—Just cast it to a double:
decimal x = 3.141592654M ;
double pi = (double) x ;