将字节数组转换为对象

Question

Is there a way in C# to convert a plain byte array to an object?

eg given this class:

class Data
{
    public int _int1;
    public int _int2;
    public short _short1;
    public long _long1;
}

I want to basically be able to do something like this:

var bytes = new byte[] { 1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 4, 0, 0, 0, 0, 0, 0, 0 };
var obj = (Data)bytes;

Answer 1

You could try marshalling:

Declare the layout of your class as Sequential (and note that you will need to use Pack = 1 ):

[StructLayout(LayoutKind.Sequential, Pack = 1)]
class Data
{
    public int _int1;
    public int _int2;
    public short _short1;
    public long _long1;
}

Marshal the bytes into a new instance of the Data class:

var bytes = new byte[] { 1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 4, 0, 0, 0, 0, 0, 0, 0 };
GCHandle gcHandle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
var data = (Data)Marshal.PtrToStructure(gcHandle.AddrOfPinnedObject(), typeof(Data));
gcHandle.Free();

// Now data should contain the correct values.

Console.WriteLine(data._int1);    // Prints 1
Console.WriteLine(data._int2);    // Prints 2
Console.WriteLine(data._short1);  // Prints 3
Console.WriteLine(data._long1);   // Prints 4

For convenience you could write a static method on Data to do the conversion:

[StructLayout(LayoutKind.Sequential, Pack = 1)]
class Data
{
    public int _int1;
    public int _int2;
    public short _short1;
    public long _long1;

    public static Data FromBytes(byte[] bytes)
    {
        GCHandle gcHandle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
        var data = (Data)Marshal.PtrToStructure(gcHandle.AddrOfPinnedObject(), typeof(Data));
        gcHandle.Free();
        return data;
    }
}

...

var data = Data.FromBytes(new byte[] {1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 4, 0, 0, 0, 0, 0, 0, 0});

If you really wanted to you could write an explicit operator to convert from an array of bytes, to get the syntax in your OP. I would suggest just using Data.FromBytes() which is going to be a lot clearer IMO.

Still, just for completeness:

[StructLayout(LayoutKind.Sequential, Pack = 1)]
class Data
{
    public int _int1;
    public int _int2;
    public short _short1;
    public long _long1;

    public static explicit operator Data(byte[] bytes)
    { 
        GCHandle gcHandle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
        var data = (Data)Marshal.PtrToStructure(gcHandle.AddrOfPinnedObject(), typeof(Data));
        gcHandle.Free();
        return data;
    }
}

...

var data = (Data)new byte[] {1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 4, 0, 0, 0, 0, 0, 0, 0};

Answer 2

Use BitConverter.ToInt32/Int16/Int64 methods. You have only have to specify the starting index like:

Data data = new Data();
data._int1 = BitConverter.ToInt32(bytes, 0);
data._int2 = BitConverter.ToInt32(bytes, 4);
data._short1 = BitConverter.ToInt16(bytes, 8);
data._long1 = BitConverter.ToInt64(bytes,10);

Just remember:

BitConverter.ToInt32

The order of bytes in the array must reflect the endianness of the computer system's architecture;

Answer 3

There is nothing that will do the conversion in one go.

But you can build on top of BitConverter :

var d = new Data();
var sI32 = sizeof(Int32);
d._int1 = BitConverter.ToInt32(bytes, 0);
d._int2 = BitConverter.ToInt32(bytes, sI32);
d._short1 = BitConverter.ToInt16(bytes, 2*sI32);
…

Answer 4

Here is a way to convert a byte array into an object.

var binaryFormatter = new BinaryFormatter();
using (var ms = new MemoryStream(bytes))
{
    object obj = binaryFormatter.Deserialize(ms);
    return (Data)obj;
}