What is the equivalent of Python's struct.pack(fmt, v1, v2, ...) in C# .NET?

Question

What is the equivalent of Python's struct.pack(fmt, v1, v2, ...) in C# .NET? I have the following struct defined in C#

[StructLayout(LayoutKind.Sequential, Pack=1)]
    struct user {
        public char id;
        public int age; 
    };

And would like to unpack it in Python application by using struct.unpack('<ci',myStringedStruct)

I was planing to use BinaryWriter into MemoryStream as suggested by Jon Skeet. However, BinaryWriter only write primitive types, and I have a struct.

Answer 1

You can write the fields one after another to the BinaryWriter:

User user = ...

using (BinaryWriter writer = ...)
{
    writer.Write((byte)user.id);
    writer.Write(user.age);
}

• BinaryWriter uses the endianness of the platform, i.e., little endian on x86/x64.
• "c – char – string of length 1 – 1 byte" is a byte in C#. Write(byte)
• "i – int – integer – 4 bytes" is an int in C#. Write(Int32)

There is no pack/unpack-like functionality built into the .NET Framework.¹

^{1. When you're p/invoking native code, there's Interop Marshaling. But you're not p/invoking native code.}