C#: How to convert long to ulong

Question

If i try with BitConverter,it requires a byte array and i don't have that.I have a Int32 and i want to convert it to UInt32.

In C++ there was no problem with that.

Somewhat confused what you're asking here buddy - longs, byte arrays, and ints - can you elaborate ? — Chris, Mar 27 '09 at 05:42

score 23 · Accepted Answer · answered Mar 27 '09 at 05:40

23

A simple cast is all you need. Since it's possible to lose precision doing this, the conversion is explicit.

long x = 10;
ulong y = (ulong)x;

answered Mar 27 '09 at 05:40

Matthew Olenik

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Isn't this possible to overflow with big negatives? You can use `unchecked` to truncate instead: http://msdn.microsoft.com/en-us/library/a569z7k8(VS.71).aspx – Josh Stodola May 26 '10 at 01:46

SirDemon · Answer 2 · 2009-03-27T05:48:04.077

7

Try:

Convert.ToUInt32()

edited Mar 27 '09 at 05:48

answered Mar 27 '09 at 05:41

SirDemon

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score 5 · Answer 3 · answered Dec 24 '14 at 13:21

Given this function:

string test(long vLong)
{
    ulong vULong = (ulong)vLong;
    return string.Format("long hex: {0:X}, ulong hex: {1:X}", vLong, vULong);
}

And this usage:

    string t1 = test(Int64.MinValue);
    string t2 = test(Int64.MinValue + 1L);
    string t3 = test(-1L);
    string t4 = test(-2L);

This will be the result:

    t1 == "long hex: 8000000000000000, ulong hex: 8000000000000000"
    t2 == "long hex: 8000000000000001, ulong hex: 8000000000000001"
    t3 == "long hex: FFFFFFFFFFFFFFFF, ulong hex: FFFFFFFFFFFFFFFF"
    t4 == "long hex: FFFFFFFFFFFFFFFE, ulong hex: FFFFFFFFFFFFFFFE"

As you can see the bits are preserved completely, even for negative values.

score 2 · Answer 4 · edited Oct 08 '15 at 13:04

2

To convert a long to a ulong, simply cast it:

long a;
ulong b = (ulong)a;

C# will NOT throw an exception if it is a negative number.

edited Oct 08 '15 at 13:04

Patrick Hofman

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answered Mar 27 '09 at 05:41

Chris

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I don't beleive that this throws an exception with a negative value, but will not be what you expect... don't have .net on here (laptop), or would test it. – Tracker1 Mar 27 '09 at 06:36
It won't, but the first bit will be interpreted as the most significant bit instead of the sign bit. – DuneCat Mar 21 '13 at 15:43
It won't throw. You should consider revise your answer otherwise it could be misleading. – KFL Apr 11 '13 at 06:21
@KFL indeed. Updated. – Patrick Hofman Oct 08 '15 at 13:05
If it throws or not is a compiler settings (Build/Advanced/Check for arithmetic overflow/underflow). To be safe you should always wrap it like `ulong b = unchecked((ulong)a)` – adrianm Nov 18 '15 at 08:40

score 1 · Answer 5 · answered Mar 27 '09 at 05:42

1

Int32 i = 17;
UInt32 j = (UInt32)i;

EDIT: question is unclear whether you have a long or an int?

answered Mar 27 '09 at 05:42

Mitch Wheat

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I think John is referring to "old" longs in C or C++ that were 32 bits wide. – Matthew Olenik Mar 27 '09 at 05:59
I meant that he referred to it out of habit. – Matthew Olenik Mar 27 '09 at 17:44

C#: How to convert long to ulong

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