C＃运算符'*'不能应用于类型'double'和'decimal'的操作数

Question

A couple errors I am struggling to understand. I am attempting to make a sales tax calculator. But keep getting operation error because I cannot multiply a decimal by decimal. Here is my code for my calulate button:

decimal decTax;
decimal decTotal;
string input;
decimal decOrder;
// Accept the order from the Console window
Console.Write("Enter order in dollars: $");
input = Console.ReadLine();
Decimal.TryParse(input, out decOrder);

// Calculate the sales tax
decTax = (0.06D  * (decOrder + decTax));
decTotal = (decOrder + decTax);
// Write the results to the Console Window
Console.WriteLine();
Console.WriteLine("The Total is " & decTotal.ToString("c"));
Console.ReadLine();

Answer 1

The error is exactly what it says. You can't multiply a decimal by your literal double 0.06D. The reason why you can't do that implicitly is because converting a decimal to a double can result in a lose of precision. The compiler won't make an automatic conversion if there is a possibility of losing precision.

Try casting it to a decimal too:

decTax = ((decimal)0.06 * (decOrder + decTax));

Or you can use the m suffix to indicate that your literal is a decimal and not a double:

decTax = 0.06m * (decOrder + decTax));

Note, however, in the code you posted in your question you never assigned an initial value to decTax . So decOrder + decTax can't be calculated. It's unclear from your question what you intended decTax to be in that case, but it needs an initial value.

Answer 2

D means Double for Decimal use M .

decTax = (0.06M  * (decOrder + decTax));

Refer to this documentation for more information.