How to invoke function from a dll?

[C# Programming]

http://www.barakasoft.com/script/Forums/Images/smiley_doh.gif dll generated by vc++
__declspec(dllexport) long __stdcall LPRLoadImage( const char* pFilePath, LPRImage** ppImage );

and LPRImage is a struct,defind as
struct LPRImage
{
int nSize;
int nChannels;
int depth;
int nColorMode;
int dataOrder;
int origin;
int width;
int height;
int imageSize;
unsigned char *pData;
int step; SYSTEMTIME timeStamp;
};

how can i call LPRLoadImage in c#,help me!!!!