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Marshaling Strings

Platform invoke copies string parameters, converting them from the .NET Framework format (Unicode) to the unmanaged format (ANSI), if needed. Because managed strings are immutable, platform invoke does not copy them back from unmanaged memory to managed memory when the function returns.

The following table lists marshaling options for strings, describes their usage, and provides a link to the corresponding .NET Framework sample.

String

Description

Sample

By value.

Passes strings as In parameters.

MsgBox

As result.

Returns strings from unmanaged code.

Strings

By reference.

Passes strings as In/Out parameters using StringBuilder.

Buffers

In a structure by value.

Passes strings in a structure that is an In parameter.

Structs

In a structure by reference (char*).

Passes strings in a structure that is an In/Out parameter. The unmanaged function expects a pointer to a character buffer and the buffer size is a member of the structure.

Strings

In a structure by reference (char[]).

Passes strings in a structure that is an In/Out parameter. The unmanaged function expects an embedded character buffer.

OSInfo

In a class by value (char*).

Passes strings in a class (a class is an In/Out parameter). The unmanaged function expects a pointer to a character buffer.

OpenFileDlg

In a class by value (char[]).

Passes strings in a class (a class is an In/Out parameter). The unmanaged function expects an embedded character buffer.

OSInfo

As an array of strings by value.

Creates an array of strings that is passed by value.

Arrays

As an array of structures that contain strings by value.

Creates an array of structures that contain strings and the array is passed by value.

Arrays

See Also

Concepts

Platform Invoke Data Types

Marshaling Classes, Structures, and Unions

Marshaling Arrays of Types

Miscellaneous Marshaling Samples

Other Resources

Marshaling Data with Platform Invoke