How to use unichar array in C# struct with DLLImport of unmanaged C

Question

I am trying to build a struct in C# to pass to unmanaged C++, I was wondering what is the correct type of variable to use for a unichar array in my struct and what it should be marshalled as.

I have already figured this out for an unsigned char array

C/C++

typedef struct _foo {
    void *fileId;
    unsigned char   fileName[15];
} foo;

C#

[StructLayout(LayoutKind.Sequential)]
public struct foo
{
   public IntPtr fileId;
   [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 15)]
   public string fileName;
}

So if I have the following in C++

typedef struct _foo {
    void *fileId;
    unichar fileName[15];   //  UTF-16LE
} foo;

What would be the correct struct to use in C#?

Answer 1

I'm guessing the same struct would do, but you need to set the DllImportAttribute.CharSet property to Auto or it will default to Ansi . Unicode would do too, but unless you are using Windows 98 or Me (no comments) Auto will marshal strings as Unicode .

Answer 2

Specify the structure as a unicode structure:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct foo
{
   public IntPtr fileId;
   [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 15)]
   public string fileName;
}