Byte array to float

Question

I am trying to cast a float into a byte array of length 4, and then back again. But I it doesn's seems to work.

Here's what I've done:

byte[] b = BitConverter.GetBytes(90);
float fb = BitConverter.ToSingle(b, 0);

I expected fb = 90, but it's 1.26E-43.

I know that my converter is little endian, so I've also tried to reverse the array, like this:

byte[] b = BitConverter.GetBytes(90);
Array.Reverse(b);
float fb = BitConverter.ToSingle(b, 0);

Then I got the answer fb = 9.0E+15.

Any ideas? Thanks in advance!

90 is an int, not a float. 90f is a float. In either case, whatever you're doing here is quite possibly the wrong thing to do -- occasionally there is a useful need for converting a float into bytes using BitConverter, but for most serialization purposes it's actually not the right tool. — Jeroen Mostert
– Jeroen Mostert, Commented Aug 26, 2019 at 13:53

D Stanley · Accepted Answer · 2019-08-26 13:53:27Z

8

BitConverter.GetBytes(90); will give you the bytes for the integer value of 90. Since you want the bytes for the float value, you need to specify that:

BitConverter.GetBytes((float)90.0);

or

BitConverter.GetBytes(90.0f);

answered Aug 26, 2019 at 13:53

D Stanley

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René Vogt · Accepted Answer · 2019-08-26 13:53:57Z

6

90 is a literal that is interpreted by the compiler as Int32, not as Single. So you call the wrong overload of GetBytes().

Use: byte[] b = BitConverter.GetBytes(90f);

to tell the compiler you want to call GetBytes(float).

answered Aug 26, 2019 at 13:53

René Vogt

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Jeroen van Langen · Accepted Answer · 2019-08-26 13:59:33Z

6

You need to change the input on the GetBytes, it's an integer now.

It's now getting the bytes on how the integer is stored and interpretate as how a float would be stored in memory.

Change it to a float.

Try:

byte[] b = BitConverter.GetBytes(90f);  // <-- add an f for floats.
Array.Reverse(b);
float fb = BitConverter.ToSingle(b, 0);

edited Aug 26, 2019 at 13:59

answered Aug 26, 2019 at 13:53

Jeroen van Langen

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