how to call functions from unmanged DLL

Another option may be this:

[DllImport(unmanaged.dll), CharSet=CharSet.Unicode, ExactSpelling=true, PreserveSig=false)]
private static extern int getdevice(ref StringBuilder pDeviceList, IntPtr pDeviceCount, ulong ulFlags);

In the example above, you would want to construct the StringBuilder with an initial capacity larger than the expected size of the return string. This can be done like the following example:

StringBuilder deviceList = new StringBuilder(256);

You are going to have to experiment with the pDeviceList parameter. The function prototype you use depends on how that parameter is used in C/C++.

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.

Aasif Eqbal Aslam
aasifaslamy85@gmail.com