C# 浮点到十进制转换

Question

Any smart way to convert a float like this:

float f = 711989.98f;

into a decimal (or double) without losing precision?

I've tried:

decimal d = (decimal)f;
decimal d1 = (decimal)(Math.Round(f,2));
decimal d2 = Convert.ToDecimal(f);

Answer 1

It's too late, the 8th digit was lost in the compiler. The float type can store only 7 significant digits. You'll have to rewrite the code, assigning to double or decimal will of course solve the problem.

Answer 2

This may be a compiler bug because it seems like a valid float should convert directly to a decimal. but it wont without losing resolution. Converting 125.609375 from float to decimal will lose resolution. However, converting it from float to double and then double to decimal will keep resolution.

    float float_val = 125.609375f;

    decimal bad_decimal_val = (decimal)float_val;   //125.6094

    double double_val = (double)float_val;
    decimal good_decimal_val = (decimal)double_val;

Answer 3

have you tried?

decimal.TryParse()

http://forums.asp.net/t/1161880.aspx

There are no implicit conversions between float/double and decimal. Implicit numeric conversions are always guaranteed to be without loss of precision or magnitude and will not cause an exception.

Answer 4

You lost precision the moment you've written 711989.98f.

711989.98 is decimal. With f in the end you are asking the compiler to convert it to float. This conversion cannot be done without losing precision.

What you probably want is decimal d = 711989.98m. This will not lose precision.

Answer 5

try this

        float y = 20;

        decimal x = Convert.ToDecimal(y/100);

        print("test: " + x);