In c# how to pass parameters while calling function when parameter is pointer to pointer

Question

as my function has parameters say---- function(char **p , int*a , uint f);
This function is actually present in my unmanaged DLL,while calling the function and passing parameters while calling function from main are
say static unsafe void Main()
{
char a='s';
int b=0;
uint ulFlags=0;

function(&a, &b, 0);
}but i get error as
Error 1 :-- The best overloaded method match for 'ConsoleApplication2.Program.XRay_SearchDevices(char**, int*, uint)' has some invalid arguments.
Error 2 :-- Argument '1': cannot convert from 'char*' to 'char**'.

aasif eqbal · Answer

Thank you well please can u send me the whole code that how to call a function from an unmanged dll. my function EXPORT_IMPORT int __cdecl getDevices ( char ** pDeviceList int * pDeviceCount unsigned long ulFlags ) this is in c++ i m working in c# and want to import dll and need to call function in my main from my unmanged dll. please note that i have to pass parametrs while calling function in main accrding to the parameterts which i have mention in my function prototype above so just send me the whole code to call this function. i have code to import my dll just ahve a look on it-- [DllImport(@C:\WINDOWS\WinSxS\unmanged.dll SetLastError = true)] public static unsafe extern int getDevices(char ** pDeviceList int * pDeviceCount uint ulFlags); i m sucessfully able to import my dll but not able to call function i m getting error Error 1 The best overloaded method match for 'ConsoleApplication2.getDevices() has some invalid arguments Error 2 Argument '1': cannot convert from 'char**' to 'ref System.Text.StringBuilder' Error 3 Argument '2': cannot convert from 'int*' to 'System.IntPtr' when i pass these parametrts let say getDevice(ref StringBuilder pDeviceList IntPtr pDeviceCount ulong ulFlags); tell me what parametrs i have to pass from my function equivalent to this arguments while calling function in main from my unmanaged dll. please note that i need to know what parametrs i have to pass from my function in order to call my function. because i have several function with parametrs of different data types. so please let me know sir abt it as soon as possible.

Sam Hobbs · Answer

Since a parameter is a pointer to a C-style string I assume that your DLL will allocate memory for the string or re-allocate memory or something such as that. So how is the memory to be freed? Since you wrote the DLL can you modify it so that it uses something else for parameters? It might be easier to use a BSTR instead of a char **.