System.Data.SQLite

          <td>If this environment variable is set [to anything], it will be
          used instead of the application base directory by the native
          library pre-loader.  This environment variable can be especially
          useful in ASP.NET and other hosted environments where direct control
          of the location of the managed assemblies is not under the control
          of the application.</td>
        </tr>
        <tr valign="top">
          <td>PreLoadSQLite_ModuleFileNameOnly</td>
          <td>If this configuration variable is set [to anything], it will be
          used as the base file name (without directory information) for the
          native SQLite module to be pre-loaded (e.g. "sqlite3.dll" or
          "libsqlite3.so.0").</td>
        </tr>
        <tr valign="top">
          <td>PreLoadSQLite_ProcessorArchitecture</td>
          <td>If this environment variable is set [to anything], it will be
          used instead of the processor architecture value contained in the
          PROCESSOR_ARCHITECTURE environment variable to help build the path
          of the native library to pre-load.</td>
        </tr>

              useful in ASP.NET and other hosted environments where direct
              control of the location of the managed assemblies is not under
              the control of the application.
    -->
    <!--
    <add key="PreLoadSQLite_BaseDirectory" value="" />
    -->

    <!--
        NOTE: If this configuration variable is set [to anything], it will be
              used as the base file name (without directory information) for
              the native SQLite module to be pre-loaded (e.g. "sqlite3.dll"
              or "libsqlite3.so.0").
    -->
    <!--
    <add key="PreLoadSQLite_ModuleFileNameOnly" value="" />
    -->

    <!--
        NOTE: If this configuration variable is set [to anything], it will be
              used instead of the processor architecture value contained in the
              PROCESSOR_ARCHITECTURE environment variable to help build the
              path of the native library to pre-load.
    -->

    protected Dictionary<SQLiteFunctionAttribute, SQLiteFunction> _functions;

#if INTEROP_VIRTUAL_TABLE
    /// <summary>
    /// This is the name of the native library file that contains the
    /// "vtshim" extension [wrapper].
    /// </summary>
    protected string _shimExtensionFileName =
        UnsafeNativeMethods.GetNativeModuleFileNameOnly();

    /// <summary>
    /// This is the name of the native entry point for the "vtshim"
    /// extension [wrapper].
    /// </summary>
    protected string _shimExtensionProcName = "sqlite3_vtshim_init";

            module.LogErrors = ((flags & SQLiteConnectionFlags.LogModuleError) == SQLiteConnectionFlags.LogModuleError);
            module.LogExceptions = ((flags & SQLiteConnectionFlags.LogModuleException) == SQLiteConnectionFlags.LogModuleException);
        }

        if (_sql == null)
            throw new SQLiteException("connection has an invalid handle");

        if (_shimExtensionFileName == null)
            throw new SQLiteException("the file name for the \"vtshim\" extension is unknown");

        if (_shimExtensionProcName == null)
            throw new SQLiteException("the entry point for the \"vtshim\" extension is unknown");

        SetLoadExtension(true);
        LoadExtension(_shimExtensionFileName, _shimExtensionProcName);

        if (module.CreateDisposableModule(_sql))
        {
            if (_modules == null)
                _modules = new Dictionary<string, SQLiteModule>();

      /// IntPtr.Zero.
      /// </summary>
      private static IntPtr _SQLiteNativeModuleHandle = IntPtr.Zero;
      #endregion

      /////////////////////////////////////////////////////////////////////////
      /// <summary>
      /// Determines the base file name (without any directory information)
      /// for the native SQLite library to be pre-loaded by this class.
      /// </summary>
      /// <returns>
      /// The base file name for the native SQLite library to be pre-loaded by
      /// this class -OR- null if its value cannot be determined.
      /// </returns>
      internal static string GetNativeModuleFileNameOnly()
      {
          string fileNameOnly = GetSettingValue(
              "PreLoadSQLite_ModuleFileNameOnly", null);

          if (fileNameOnly != null)
              return fileNameOnly;

          return SQLITE_DLL;
      }

      /////////////////////////////////////////////////////////////////////////
      /// <summary>
      /// Searches for the native SQLite library in the directory containing
      /// the assembly currently being executed as well as the base directory
      /// for the current application domain.
      /// </summary>
      /// <param name="baseDirectory">
      /// Upon success, this parameter will be modified to refer to the base
      /// directory containing the native SQLite library.

      {
          if (GetSettingValue(
                "PreLoadSQLite_NoSearchForDirectory", null) != null)
          {
              return false; /* DISABLED */
          }

          //
          // NOTE: Determine the base file name for the native SQLite library.
          //       If this is not known by this class, we cannot continue.
          //
          string fileNameOnly = GetNativeModuleFileNameOnly();

          if (fileNameOnly == null)
              return false;

          //
          // NOTE: Build the list of base directories and processor/platform
          //       names.  These lists will be used to help locate the native
          //       SQLite core library (or interop assembly) to pre-load into
          //       this process.
          //
          string[] directories = {

              foreach (string subDirectory in subDirectories)
              {
                  if (subDirectory == null)
                      continue;

                  string fileName = FixUpDllFileName(MaybeCombinePath(
                      MaybeCombinePath(directory, subDirectory),
                      fileNameOnly));

                  //
                  // NOTE: If the SQLite DLL file exists, return success.
                  //       Prior to returning, set the base directory and
                  //       processor architecture to reflect the location
                  //       where it was found.
                  //

          //
          // NOTE: If we failed to query the base directory, stop now.
          //
          if (baseDirectory == null)
              return false;

          //
          // NOTE: Determine the base file name for the native SQLite library.
          //       If this is not known by this class, we cannot continue.
          //
          string fileNameOnly = GetNativeModuleFileNameOnly();

          if (fileNameOnly == null)
              return false;

          //
          // NOTE: If the native SQLite library exists in the base directory
          //       itself, stop now.
          //
          string fileName = FixUpDllFileName(MaybeCombinePath(baseDirectory,
              fileNameOnly));

          if (File.Exists(fileName))
              return false;

          //
          // NOTE: If the specified processor architecture is null, use the
          //       default.

              return false;

          //
          // NOTE: Build the full path and file name for the native SQLite
          //       library using the processor architecture name.
          //
          fileName = FixUpDllFileName(MaybeCombinePath(MaybeCombinePath(
              baseDirectory, processorArchitecture), fileNameOnly));

          //
          // NOTE: If the file name based on the processor architecture name
          // is not found, try using the associated platform name.
          //
          if (!File.Exists(fileName))
          {

                  return false;

              //
              // NOTE: Build the full path and file name for the native SQLite
              //       library using the platform name.
              //
              fileName = FixUpDllFileName(MaybeCombinePath(MaybeCombinePath(
                  baseDirectory, platformName), fileNameOnly));

              //
              // NOTE: If the file does not exist, skip trying to load it.
              //
              if (!File.Exists(fileName))
                  return false;
          }