为什么从 DLL 调用不安全的函数会使一切崩溃

请告诉我调用函数时我做错了什么？：

static class NativeMethods
{
    [DllImport("kernel32.dll")]
    public static extern IntPtr LoadLibrary(string dllToLoad);

    [DllImport("kernel32.dll")]
    public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName);

    [DllImport("kernel32.dll")]
    public static extern bool FreeLibrary(IntPtr hModule);
}

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate IntPtr CreateSemaphore(uint dwDesiredAccess, long lInitialCount, long lMaximumCount, string lpName);


IntPtr pDll = NativeMethods.LoadLibrary(@"kernel32.dll");
IntPtr pAddressOfFunctionToCall = NativeMethods.GetProcAddress(pDll, "CreateSemaphoreA");
CreateSemaphore createSemaphore = (CreateSemaphore)Marshal.GetDelegateForFunctionPointer(pAddressOfFunctionToCall, typeof(CreateSemaphore));
IntPtr theResult = createSemaphore(0,2,2,"qwerty");

我也尝试使用 PInvoke 来做：

[DllImport("kernel32.dll", SetLastError = true)]
public static extern HANDLE CreateSemaphore(uint dwDesiredAccess, long lInitialCount, long lMaximumCount, string lpName);

IntPtr result = winapi.CreateSemaphore(0,0,3,"qwerty");

错误是可以更改内存等，但是我运行 CreateMutex (public static extern IntPtr CreateMutex(IntPtr lpMutexAttributes, bool bInitialOwner, string lpName)) ，一切都很好（（（（

升级版：

        [UnmanagedFunctionPointer(CallingConvention.StdCall,CharSet = CharSet.Ansi)]
        private delegate IntPtr CreateSemaphore(IntPtr dwDesiredAccess, long lInitialCount, long lMaximumCount, string lpName);

        IntPtr pDll = NativeMethods.LoadLibrary(@"kernel32.dll");
        IntPtr pAddressOfFunctionToCall = NativeMethods.GetProcAddress(pDll, "CreateSemaphoreA");
        CreateSemaphore createSemaphore = (CreateSemaphore)Marshal.GetDelegateForFunctionPointer(pAddressOfFunctionToCall, typeof(CreateSemaphore));
        IntPtr theResult = createSemaphore(new IntPtr(),2,2,"qwerty");