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C Dll Import throws Marshall Directive exception in C #

I have a problem including a DLL (written in C) in my C # project, and I hope you can help me. In my research, I found DLLImport, but I'm not sure which types of C variables are converted to ...

The C method from the DLL I want to import is as follows:

int lou_translateString (
     const char * tableList,
     const widechar * inbuf,
     int *inlen,
     widechar *outbuf,
     int *outlen,
     char *typeform,
     char *spacing,
     int mode);

This is the DLLImport I tried:

[DllImport("liblouis-2.dll", EntryPoint = "lou_translateString", CharSet = CharSet.Ansi, ExactSpelling = true)]
    [return: MarshalAs(UnmanagedType.LPStr)]
    public static extern int translate([MarshalAs(UnmanagedType.LPStr)]
        String tableList,
        String inbuf,
        int inlen,
        String outbuf,
        int outlen,
        String typeform,
        String spacing,
        int mode);

But when I try to call a method, I get:

MarshallDirectiveException Cannot marshal "return value": invalid combination of managed / unmanaged types (Int32 / UInt32 must be mated to I4 or U4)

Can anyone help with an exception? I am sure that this is due to the types of parameters in the method, but I do not know how to declare them correctly. Any help would be appreciated!

Thanks in advance Alex

Added shorted documentation to clarify

16- Unicode inbuf 16- outbuf.

tableList .

, * inlen * outlen . , , . , .

typeform , , .. , * inbuf. , * outlen. typeform . : 0 plain-text; 1 ; 2 ; 4 ; 8 . . NULL, . , NULL, 8 , outbuf, , 7, 8 , .

. , , * inbuf. NULL, .

mode , .

1, 0, .

, Main:

        StringBuilder outbuf = new StringBuilder("Test", 30);
        int inlength = 100;
        int louint = 0;
        int outlength = 100;
        String inbuf = "test";


        louint = lou_translateString("de-de-g1.ctb", inbuf, inlen: ref inlength, outbuf: outbuf, outlen: ref outlength, typeform: null, spacing: null, mode: 8);

. , ? - outbuf, StringBuilder, String (outbuf.Replace())?

+4
1

MarshalAs . int, . , . pinvoke . :

[DllImport("liblouis-2.dll", CharSet = CharSet.Unicode)]
public static extern int lou_translateString(
    [MarshalAs(UnmanagedType.LPStr)]
    string tableList,
    string inbuf,
    ref int inlen,
    StringBuilder outbuf,
    ref int outlen,
    [MarshalAs(UnmanagedType.LPStr)]
    StringBuilder typeform,
    [MarshalAs(UnmanagedType.LPStr)]
    StringBuilder spacing,
    int mode
);

, , StringBuilder. . int* ref int.

, StringBuilder outbuf. , . , , . , null typeform spacing.

+2

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