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copied!<p>A blittable type is a type that has a common representation between managed and unmanaged code and can therefore be passed between them with little or no problem, e.g. byte, int32, etc. </p> <p>A non-blittable type does not have the common representation, e.g. System.Array, System.String, System.Boolean, etc. </p> <p>By specifying the MarshalAs attribute for a non-blittable type you can tell the marshaller what it should be converted to. See this <a href="http://msdn.microsoft.com/en-us/library/75dwhxf7%28v=VS.100%29.aspx" rel="nofollow">article on Blittable and Non-Blittable Types</a> for more information</p> <blockquote> <p>1 - What is the best way to pass strings? Some are short (device id's which can be set by us), and some are file paths (which may contain Asian characters)</p> </blockquote> <p>StringBuilder is generally recommended as the easiest to use but I often use plain byte arrays.</p> <blockquote> <p>2 - Should I pass an IntPtr to the C# struct or should I just let the Marshaller take care of it by putting the struct type in the function signature?</p> </blockquote> <p>If the method is expecting a pointer then pass an IntPtr although you can get probably away with a ref in many cases depending on what it's going to be used for. If it's something that needs to stick around in the same place for a long time then I would manually allocate the memory with Marshal and pass the resulting IntPtr.</p> <blockquote> <p>3 - Should I be worried about any non-pointer datatypes like bools or enums (in other, related structs)? We have the treat warnings as errors flag set in C++ so we can't use the Microsoft extension for enums to force a datatype.</p> </blockquote> <p>Once you've got everything set up with the correct marshalling attributes I don't see why you'd need to worry. If in doubt put in the attribute, if the struct only ever gets used by managed code then the attribute won't be used.</p> <blockquote> <p>4 - Is P/Invoke actually the way to go? There was some Microsoft documentation about Implicit P/Invoke that said it was more type-safe and performant. </p> </blockquote> <p>Can't comment on this, you're into Visual C++ territory there.</p>

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