Pointers in C# to Retrieve Reference From DllImport Function

Question

I am referencing a DLL in my C# project as follows:

[DllImport("FeeCalculation.dll", CallingConvention = CallingConvention.StdCall,
           CharSet = CharSet.Ansi)]

        public static extern void FeeCalculation(string cin, string cout, string flimit,
            string frate, string fwindow, string fincrement, string fbird, 
            string fparameter, string fvalidation, string fcoupon);

The FeeCalculation function is exported as follows in the DLL:

extern "C" __declspec(dllexport) void __stdcall FeeCalculation(char *cin, 
char *cout, char *flimit, char *frate,
char *fwindow, char *fincrement, char *fbird,
char *fparameter, char *fvalidation, char *fcoupon);

The DLL function returns a reference to it's internal structures in the form of char * so if you were to reference this DLL in C++, you would do the following to do the calculation and get the returned structures:

FeeCalculation(buff, (char *)&fans, (char *)fl, (char *)ft, (char *)fw, (char *)fi, (char *)fe, (char *)&fm, (char *)val, (char *)cpn);

Now, how do I retrieve those values that are returned by reference using C#? Meaning, how do I do the same thing in C# to get the returned structures to get my returned calculation? I know I need to create an unsafe method, but I am unclear on how to deal with the memory addresses in C# like you would in C++.

Edit: Below states to use IntPtr but how do you place into identical structure so the fields of the structure can be referenced?

Edit: Here is the returned structure that I am interested in (cout):

struct feeAnswer {


    unsigned int    fee;

    unsigned int    tax1;

    unsigned int    tax2;

    unsigned int    tax3;

    unsigned int    tax4;

    unsigned int    surcharge1;

    unsigned int    surcharge2;

    unsigned int    validationFee;

    unsigned int    couponFee1;

    unsigned int    couponFee2;

    unsigned int    couponFee3;

    unsigned int    couponFee4;

    unsigned short int dstay;       //Day Stay

    unsigned short int mstay;       //Minute Stay

};

Here is the (cin) that I would pass along with other structures (they are zero byte at the moment, I want to get this to work first then I will implement the rest):

struct feeRequest {

    unsigned char   day;

    unsigned char   month;

    unsigned int    year;   //2000 ~ 2099



    unsigned char   hour;

    unsigned char   minute;

    unsigned char   rate;

    unsigned char   validation;



    unsigned char   coupon1;

    unsigned char   coupon2;

    unsigned char   coupon3;

    unsigned char   coupon4;

};

Answer 1

MSDN의 설명서를 기반으로 오래된 정규 방법을 사용하여 수행 할 수 없습니다.

Visual Web Parts는 $ spurl 과 같은 SharePoint Server 토큰을 직접 지원하지 않습니다.자세한 내용은 "Sandboxed Visual Web Parts의 토큰 제한 사항"을 참조하십시오.

Visual Web Parts 샌드 박스 솔루션은 SharePoint 런타임이 지원하는 $ spurl과 같은 표준 토큰을 처리 할 수 없습니다.결과적으로 URL이 해결되지 않고 다음 예제와 같이 스크립트 요소에서 직접 참조하는 경우 Visual Web Part Designer에서 디자인보기에서 콘텐츠를 미리 볼 수 없습니다.

<script src=”<% $SPUrl:~site/SiteAssets/ListOperations.js %>"></script>

.

이 제한을 해결하고 토큰을 해결하려면 리터럴을 사용하여 참조하십시오.

<asp:literal ID="Literal1" runat="server" Text="&lt;script src='" />
<asp:literal ID="Literal2" runat="server" Text="<% $SPUrl:~site/SiteAssets/ListOperations.js %>" />
<asp:literal ID="Literal3" runat="server" Text="' type='text/javascript' &gt;&lt;/script&gt;" />  

.

MSDN에 대한 추가 정보 : SharePoint 솔루션 문제 해결

Answer 2

The char* parameters in this case are not strings but pointers to chunks of raw bytes representing the data. You should marshal your parameters as instances of the IntPtr type, in conjunction with Marshal.AllocHGlobal to create a chunk of memory and then Marshal.PtrToStructure to convert that block of memory into a usable .NET type.

As an example:

[StructLayout(LayoutKind.Sequential)]
struct MyUnmanagedType
{
    public int Foo;
    public char C;
}

IntPtr memory = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(MyUnmanagedType)));

try
{
    FeeCalculation(memory);

    MyUnmanagedType result = (MyUnmanagedType)Marshal.PtrToStructure(
        memory, typeof(MyUnmanagedType));
}
finally
{
    Marshal.FreeHGlobal(memory);
}

Answer 3

To answer your Edit, you need to create a struct, and then use the StructLayoutAttribute on the fields in order to make the byte order and padding the same as the original dll did.