String of decimal numbers to byte array [c#]

Question

I have problem in c# with convert decimal number from string to byte array. I want creat BigInteger with using byte array.

I try:

string Astr = "123456789123456789123456789123456789123456789123456789123456789123456789123456789";
byte[] AByte = Astr.Select(c => (byte)(c - '0')).ToArray(); //This is problem because array padding wrong.

Tnaks for your ideas. :)

So one idea: a single decimal digit does not occupy one full byte. — Ondrej Tucny
– Ondrej Tucny, Commented Feb 12, 2014 at 11:14
I don't understand your question clearly but BigInteger structure has an Byte array constructor. Did you tried it? Note: It is not a CLS compliant. — Soner Gönül
– Soner Gönül, Commented Feb 12, 2014 at 11:15
BigInteger in c# is small - I need work with cca 2048 bit numbers. — user3299032
– user3299032, Commented Feb 12, 2014 at 11:31

Matthew Watson · Accepted Answer · 2014-02-12 11:23:47Z

1

Why do you need to create the BigInteger from a byte array when you have the string available?

Why not just do this?

string aStr = "123456789123456789123456789123456789123456789123456789123456789123456789123456789";
BigInteger x = BigInteger.Parse(aStr);

Also note that there is no easy correspondence between a BigInteger in string form and its byte array.

For example, following on from the code above, if you add this:

var ba = x.ToByteArray();
Console.WriteLine(string.Join(" ", ba.Select(v => v.ToString("x"))));

The output is:

15 5f 4 84 b6 70 28 c7 73 7b a3 d5 f9 b a1 8 67 12 b0 a5 af 52 ba cb e4 66 6c 75 78 66 92 31 2a 4

Which is the byte[] version of the original string after being encoded as a BigInteger.

edited Feb 12, 2014 at 11:23

answered Feb 12, 2014 at 11:18

Matthew Watson

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2 Comments

user3299032 Over a year ago

BigInteger in c# is small for me :( - I need work with cca 2048 bit numbers.

Matthew Watson Over a year ago

@user3299032 But C# integer works with 2048 bit numbers (and much more), so what is your actual problem?

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