How to fix the LibraryImport issue?

Question

I have been trying to use this code in the WPF application developed using .NET 7.

        [DllImport("user32.dll")]
        internal static extern bool InsertMenu(IntPtr Menu, Int32 Position, Int32 Flags, Int32 IDNewItem, string NewItem);

However I get the SYSLIB1054 message : "Mark the method 'InsertMenu' with 'LibraryImportAttribute' instead of 'DllImportAttribute' to generate P/Invoke marshalling code at compile time"

I changed the code as below

        [LibraryImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        internal static partial bool InsertMenu(IntPtr Menu, Int32 Position, Int32 Flags, Int32 IDNewItem, [MarshalAs(UnmanagedType.LPUTF8Str)] string NewItem);

Then I get this error : "Unable to find an entry point named 'InsertMenu' in DLL 'user32.dll'."

How do I fix this?

Answer 1

To upgrade DllImport functions related to charset, firstly specify the charset property to Unicode:

[DllImport("user32.dll", CharSet = CharSet.Unicode)]

Next choose the second suggestion:

• Convert to 'LibraryImport' with 'W' suffix

Then you will get:

[LibraryImport("user32.dll", EntryPoint = "InsertMenuW", StringMarshalling = StringMarshalling.Utf16)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static partial bool InsertMenu(IntPtr Menu, Int32 Position, Int32 Flags, Int32 IDNewItem, string NewItem);

If you want to call the ANSI version, the process is the same as above.