VB.NET Convert 4 bytes to an integer [duplicate]

Question

Windows 11 U.S.

VB.NET, How can I convert 4 bytes in a byte array to an integer value?

I can figure out how to do two bytes using something like

IntValue = (mybyte(0) * 256) Or mybyte(1)

So if mybyte(0) = 3 and mybyte(1) = 232, or the hex equiv number 03E8, it would be int=1000.

How can I do this if I have 4 bytes? mybyte(0)..(3).

So if I had myByte(0) = 64 and the rest of the bytes (x) are 0, or the hex equiv number of 40000000, it would equal 1,073,741,824.

I tried other suggestions:

intval = Bitconverter.Toint32(mybyte, 0)

... all I get is 64.

I also tried

Dim combined As UInteger = CType(((mybyte(0) << 24) Or (mybyte(1) << 16) Or (mybyte(2) << 8) Or (mybyte(3) << 0)), UInteger)

... all I get is 64

expecting 1,073,741,824

Answer 1

Since you also tagged C# originally (before the tags were editted), here's a solution in C# (which I assume you can convert easily to VB.NET).

Using BitConverter that you mentioned is indeed the way to go.

The following example is based on the documentation from MS: How to convert a byte array to an int:

byte[] bytes = new byte[] { 64, 0, 0, 0 };

// If the system architecture is little-endian (that is, little end first),
// reverse the byte array.
if (BitConverter.IsLittleEndian)
    Array.Reverse(bytes);

int i = BitConverter.ToInt32(bytes, 0);
Console.WriteLine("int: {0}", i);

Output:

int: 1073741824

Note the proper handling of Endianness to make sure the bytes are treated in the right order.

Live demo

Answer 2

When the elements of mybyte are of type Byte, doing mybyte(0)) << 24 results in a Byte, which is no good because all the bits get lost. That operator gives a result of the same type as the left operand.

You need to convert each element to the type you want to get out at the end:

Dim a = CUInt(mybyte(0)) << 24 Or CUInt(mybyte(1)) << 16 Or CUInt(mybyte(2) << 8) Or mybyte(3)

(Arithmetic bit shift has a higher precedence than bitwise operators. The final byte doesn't need to be converted to a different type.)

There was some inconsistency in the question as to whether an integer or unsigned integer was needed: change the occurrences of CUInt to CInt if the former.

If you use * and + operators, you could do

Dim b = (((mybyte(0) * 256 + mybyte(1)) * 256) + mybyte(2)) * 256 + mybyte(3)

or

Dim c = mybyte(0) * 16777216 + mybyte(1) * 65536 + mybyte(2) * 256 + mybyte(3)

which work without conversions because the multipliers 16777216, 65536, and 256 are of type Integer.

Or you could just use:

Dim n = BitConverter.ToInt32(mybyte.Reverse().ToArray(), 0)

Finally, if you're using .NET Core 2.1 or later, it's really easy:

Dim d = BinaryPrimitives.ReadInt32BigEndian(mybyte)

Docs: BinaryPrimitives Class—"Use these helpers when you need to read specific endianness."