/// <summary>
/// Ensures that the LocalDB native API has been loaded.
/// </summary>
/// <returns>
/// A <see cref="SafeLibraryHandle"/> pointing to the loaded
/// SQL LocalDB API, if successful; otherwise <see langword="null"/>.
/// </returns>
private SafeLibraryHandle EnsureLocalDBLoaded()
{
if (_handle == null)
{
lock (_syncRoot)
{
if (_handle == null)
{
if (!TryGetLocalDbApiPath(out string fileName))
{
return(null);
}
int dwFlags = 0;
// Check if the local machine has KB2533623 installed in order
// to use the more secure flags when calling LoadLibraryEx
bool hasKB2533623;
using (var hModule = NativeMethods.LoadLibraryEx(NativeMethods.KernelLibName, IntPtr.Zero, 0))
{
// If the AddDllDirectory function is found then the flags are supported
hasKB2533623 = NativeMethods.GetProcAddress(hModule, "AddDllDirectory") != IntPtr.Zero;
}
if (hasKB2533623)
{
// If KB2533623 is installed then specify the more secure LOAD_LIBRARY_SEARCH_DEFAULT_DIRS in dwFlags
dwFlags = NativeMethods.LOAD_LIBRARY_SEARCH_DEFAULT_DIRS;
}
_handle = NativeMethods.LoadLibraryEx(fileName, IntPtr.Zero, dwFlags);
if (_handle == null || _handle.IsInvalid)
{
int error = Marshal.GetLastWin32Error();
Logger.NativeApiLoadFailed(fileName, error);
_handle = null;
}
else
{
Logger.NativeApiLoaded(fileName);
_libraryPath = fileName;
}
}
}
}
return(_handle);
}
/// <summary>
/// Returns a delegate of the specified type to the specified unmanaged function.
/// </summary>
/// <typeparam name="T">The type of the delegate to return.</typeparam>
/// <param name="functionName">The name of the unmanaged function.</param>
/// <returns>
/// An instance of <typeparamref name="T"/> that points to the specified unmanaged
/// function, if found; otherwise <see langword="null"/>.
/// </returns>
private T GetDelegate <T>(string functionName)
where T : Delegate
{
Debug.Assert(functionName != null, "functionName cannot be null.");
SafeLibraryHandle handle = EnsureLocalDBLoaded();
if (handle == null)
{
Logger.NativeApiNotLoaded();
return(null);
}
IntPtr ptr = NativeMethods.GetProcAddress(handle, functionName);
if (ptr == IntPtr.Zero)
{
Logger.NativeApiFunctionNotFound(functionName);
return(null);
}
return(Marshal.GetDelegateForFunctionPointer <T>(ptr));
}
internal static extern IntPtr GetProcAddress(
SafeLibraryHandle hModule,
[MarshalAs(UnmanagedType.LPStr)] string lpProcName);