Marshalling array of structures from C#.

Question

Hey folks,

I have a requirement where I need to marshal an array of structures from managed code(c#) to native code(C++). The structure is something like

//need to put any attributes here?

public struct inner
{
    [MarshalAs(UnmanagedType.U8)]
    public long l1;
    [MarshalAs(UnmanagedType.U8)]
    public long l2;
}

public struct outer
{    
    [MarshalAs(UnmanagedType.LPWStr)]
    public string s1;
    [MarshalAs(UnmanagedType.U4)]
    public int i1;
    [MarshalAs(UnmanagedType.U4)]
    public int i2;
    [MarshalAs(UnmanagedType.U8)]
    public long l1;
    // How can I marshal an array of structures here?
    public inner[] array1;
}

My requirement is to return an array of the struct outer :)

Can anyone help me out?

Thanks in Advance, -Mani.

Answer 1

I think you're after StructLayoutKind.Sequential ?

MSDN Struct Tutorial

StructLayoutKind reference

Answer 2

Without seeing the unmanaged declarations and the associated semantics expected by the corresponding methods which uses them, it impossible to tell, but you will need:

[MarshalAs(UnmanagedType.LPArray, SizeConst=10)] //change size as per your needs
public inner[] array1;

OR

[MarshalAs(UnmanagedType.ByValArray, SizeConst=10)] //change size as per your needs
public inner[] array1;

Answer 3

Add a C++/CLI assembly to your project. That's the easiest way to do interop with C++. Then you can directly include all your .h files and link to any .lib files. But you're still i .NET-land. C++/CLI is very similar to C#. You just have to type a ""^ after all your managed classes and you use "->" instead of "." but that's about it... :-)