C＃：如何从对象变量中的值获取类型变量并在类型变量中输入类型？

Question

1. I have a value in a variable of type Object .
2. I have its type in a variable of type Type .
3. Type can be only among standard system types (Int32, Int64, etc..)

Q. I want to get bytes array representing this value. I'm trying to use BitConverter.GetBytes for that, but it requires a typed variable. Is there a way to get typed variable dynamically having a value and type in separate variables?

Thank you.

Answer 1

If you don't want to switch on each type and call the appropriate method, which is the fastest way, you could use reflection, albeit a bit slower:

byte[] GetBytes(object obj)
{
    var type = obj.GetType();
    return (byte[])typeof(BitConverter)
        .GetMethods(BindingFlags.Public | BindingFlags.Static)
        .Single(m => m.Name == "GetBytes" && m.GetParameters().Single().ParameterType == type)
        .Invoke(null, new object[] { obj });
}

Calling GetBytes((short)12345) produces new byte[] { 0x39 ,0x30 } .

Answer 2

public byte[] GetAnyBytes(dynamic myVariable) {
     return BitConverter.GetBytes(myVariable)
}

dynamic is essentially "I don't know what type this could be, check it at run time". Obviously, this is slower than using real types, but it is more flexible. Also, requires C# 4.0.

Answer 3

You could try something like this to get a byte array.

public static byte[] Object2ByteArray(object o)
{
    using (System.IO.MemoryStream ms = new System.IO.MemoryStream())
    {
        System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bf = 
            new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
        bf.Serialize(ms, o);
        return ms.ToArray();
    }
}

Although based on your description you may have made some poor implementation choices elsewhere.

found here .

Answer 4

I'm concerned that you're trying to interact with another device using a binary format. Assuming the receiver of your data is not .NET, binary representations of data types varies from one device to another. I think you're better off representing this information in text, and using a parser to interpret the text.

Answer 5

You can use MemoryMappedFile

private byte[] GetBytes<T>(T obj) where T : struct
{
    int size = Marshal.SizeOf(typeof(T));
    using(var mmf = MemoryMappedFile.CreateNew("test", size))
    using(var acc = mmf.CreateViewAccessor())
    {
        acc.Write(0, ref obj);
        var arr = new byte[size];
        for (int i = 0; i < size; i++)
            arr[i] = acc.ReadByte(i);
        return arr;
    }
}