Exception r = returnValue as Exception;

        if (r != null)
        {
          _base.ReturnError(context, r.Message);
          return;
        }
      }

      switch (SQLiteConvert.TypeToAffinity(t))
      {
        case TypeAffinity.Null:
          _base.ReturnNull(context);
          return;
        case TypeAffinity.Int64:
          _base.ReturnInt64(context, Convert.ToInt64(returnValue, CultureInfo.CurrentCulture));
          return;
        case TypeAffinity.Double:
          _base.ReturnDouble(context, Convert.ToDouble(returnValue, CultureInfo.CurrentCulture));
          return;
        case TypeAffinity.Text:
          _base.ReturnText(context, returnValue.ToString());
          return;
        case TypeAffinity.Blob:
          _base.ReturnBlob(context, (byte[])returnValue);
          return;
      }
    }

    /// <summary>
    /// Internal scalar callback function, which wraps the raw context pointer and calls the virtual Invoke() method.
    /// </summary>
    /// <param name="context">A raw context pointer</param>
    /// <param name="nArgs">Number of arguments passed in</param>
    /// <param name="argsptr">A pointer to the array of arguments</param>
    internal void ScalarCallback(IntPtr context, int nArgs, IntPtr argsptr)
    {
      SetReturnValue(context, Invoke(ConvertParams(nArgs, argsptr)));
    }

    /// <summary>
    /// Internal collation sequence function, which wraps up the raw string pointers and executes the Compare() virtual function.
    /// </summary>
    /// <param name="len1">Length of the string pv1</param>
    /// <param name="ptr1">Pointer to the first string to compare</param>
    /// <param name="len2">Length of the string pv2</param>
    /// <param name="ptr2">Pointer to the second string to compare</param>
    /// <returns>Returns -1 if the first string is less than the second.  0 if they are equal, or 1 if the first string is greater
    /// than the second.</returns>
    internal int CompareCallback(int len1, IntPtr ptr1, int len2, IntPtr ptr2)
    {
      return Compare(_base.ToString(ptr1, len1), _base.ToString(ptr2, len2));
    }

    /// <summary>
    /// The internal aggregate Step function callback, which wraps the raw context pointer and calls the virtual Step() method.
    /// </summary>
    /// <remarks>
    /// This function takes care of doing the lookups and getting the important information put together to call the Step() function.
    /// That includes pulling out the user's contextData and updating it after the call is made.  We use a sorted list for this so
    /// binary searches can be done to find the data.
    /// </remarks>
    /// <param name="context">A raw context pointer</param>
    /// <param name="nArgs">Number of arguments passed in</param>
    /// <param name="argsptr">A pointer to the array of arguments</param>
    internal void StepCallback(IntPtr context, int nArgs, IntPtr argsptr)
    {
      int n = _base.AggregateCount(context);
      long nAux;
      object obj = null;

      nAux = (long)_base.AggregateContext(context);
      if (n > 1) obj = _contextDataList[nAux];

      Step(ConvertParams(nArgs, argsptr), n, ref obj);
      _contextDataList[nAux] = obj;      
    }

    /// <summary>
    /// An internal aggregate Final function callback, which wraps the context pointer and calls the virtual Final() method.
    /// </summary>
    /// <param name="context">A raw context pointer</param>
    /// <param name="nArgs">Not used, always zero</param>
    /// <param name="argsptr">Not used, always zero</param>
    internal void FinalCallback(IntPtr context, int nArgs, IntPtr argsptr)
    {
      long n = (long)_base.AggregateContext(context);
      object obj = null;

      if (_contextDataList.ContainsKey(n))
      {
        obj = _contextDataList[n];
        _contextDataList.Remove(n);
      }

      SetReturnValue(context, Final(obj));

      IDisposable disp = obj as IDisposable;
      if (disp != null) disp.Dispose();
    }

    /// <summary>
    /// Placeholder for a user-defined disposal routine
    /// </summary>
    /// <param name="disposing">True if the object is being disposed explicitly</param>
    protected virtual void Dispose(bool disposing)
    {
    }

    /// <summary>
    /// Disposes of any active contextData variables that were not automatically cleaned up.  Sometimes this can happen if
    /// someone closes the connection while a DataReader is open.
    /// </summary>
    public void Dispose()
    {
      Dispose(true);

      IDisposable disp;

      foreach (KeyValuePair<long, object> kv in _contextDataList)
      {
        disp = kv.Value as IDisposable;
        if (disp != null)
          disp.Dispose();
      }
      _contextDataList.Clear();

      _InvokeFunc = null;
      _StepFunc = null;
      _FinalFunc = null;
      _CompareFunc = null;
      _base = null;
      _contextDataList = null;

      GC.SuppressFinalize(this);
    }

#if !PLATFORM_COMPACTFRAMEWORK
    /// <summary>
    /// Using reflection, enumerate all assemblies in the current appdomain looking for classes that
    /// have a SQLiteFunctionAttribute attribute, and registering them accordingly.
    /// </summary>
    static SQLiteFunction()
    {
      SQLiteFunctionAttribute at;
      System.Reflection.Assembly[] arAssemblies = System.AppDomain.CurrentDomain.GetAssemblies();
      int w = arAssemblies.Length;

      for (int n = 0; n < w; n++)
      {
        Type[] arTypes;
        try
        {
          arTypes = arAssemblies[n].GetTypes();
        }
        catch (Reflection.ReflectionTypeLoadException e)
        {
          arTypes = e.Types;
        }

        int v = arTypes.Length;
        for (int x = 0; x < v; x++)
        {
          if (arTypes[x] == null) continue;

          object[] arAtt = arTypes[x].GetCustomAttributes(typeof(SQLiteFunctionAttribute), false);
          int u = arAtt.Length;
          for (int y = 0; y < u; y++)
          {
            at = arAtt[y] as SQLiteFunctionAttribute;
            if (at != null)
            {
              at._instanceType = arTypes[x];
              _registeredFunctions.Add(at);
            }
          }
        }
      }
    }
#else
    /// <summary>
    /// Manual method of registering a function.  The type must still have the SQLiteFunctionAttributes in order to work
    /// properly, but this is a workaround for the Compact Framework where enumerating assemblies is not currently supported.
    /// </summary>
    /// <param name="typ">The type of the function to register</param>
    public static void RegisterFunction(Type typ)
    {
      object[] arAtt = typ.GetCustomAttributes(typeof(SQLiteFunctionAttribute), false);
      int u = arAtt.Length;
      SQLiteFunctionAttribute at;

      for (int y = 0; y < u; y++)
      {
        at = arAtt[y] as SQLiteFunctionAttribute;
        if (at != null)
        {
          at._instanceType = typ;
          _registeredFunctions.Add(at);
        }
      }
    }
#endif

    /// <summary>
    /// Called by SQLiteBase derived classes, this function binds all user-defined functions to a connection.
    /// It is done this way so that all user-defined functions will access the database using the same encoding scheme
    /// as the connection (UTF-8 or UTF-16).
    /// </summary>
    /// <remarks>
    /// The wrapper functions that interop with SQLite will create a unique cooke value, which internally is a pointer to
    /// all the wrapped callback functions.  The interop function uses it to map CDecl callbacks to StdCall callbacks.
    /// </remarks>
    /// <param name="sqlbase">The base object on which the functions are to bind</param>
    /// <returns>Returns an array of functions which the connection object should retain until the connection is closed.</returns>
    internal static SQLiteFunction[] BindFunctions(SQLiteBase sqlbase)
    {
      SQLiteFunction f;
      List<SQLiteFunction> lFunctions = new List<SQLiteFunction>();

      foreach (SQLiteFunctionAttribute pr in _registeredFunctions)
      {
        f = (SQLiteFunction)Activator.CreateInstance(pr._instanceType);
        f._base = sqlbase;
        f._InvokeFunc = (pr.FuncType == FunctionType.Scalar) ? new SQLiteCallback(f.ScalarCallback) : null;
        f._StepFunc = (pr.FuncType == FunctionType.Aggregate) ? new SQLiteCallback(f.StepCallback) : null;
        f._FinalFunc = (pr.FuncType == FunctionType.Aggregate) ? new SQLiteCallback(f.FinalCallback) : null;
        f._CompareFunc = (pr.FuncType == FunctionType.Collation) ? new SQLiteCollation(f.CompareCallback) : null;

        if (pr.FuncType != FunctionType.Collation)
          f._interopCookie = sqlbase.CreateFunction(pr.Name, pr.Arguments, f._InvokeFunc, f._StepFunc, f._FinalFunc);
        else
          f._interopCookie = sqlbase.CreateCollation(pr.Name, f._CompareFunc);


        lFunctions.Add(f);
      }

      SQLiteFunction[] arFunctions = new SQLiteFunction[lFunctions.Count];
      lFunctions.CopyTo(arFunctions, 0);

      return arFunctions;
    }

    /// <summary>
    /// Issued after the base connection is closed, this function cleans up all user-defined functions and disposes of them.
    /// </summary>
    /// <remarks>
    /// Cleaning up here is done mainly because of the interop wrapper.  It allocated memory to hold a reference to all the
    /// delegates, and now must free that memory.
    /// Freeing is done after the connection is closed to ensure no callbacks get hit after we've freed the cookie.
    /// </remarks>
    /// <param name="sqlbase">The base SQLite connection object</param>
    /// <param name="ar">An array of user-defined functions for this object</param>
    internal static void UnbindFunctions(SQLiteBase sqlbase, SQLiteFunction[] ar)
    {
      if (ar == null) return;

      int x = ar.Length;
      for (int n = 0; n < x; n++)
      {
        sqlbase.FreeFunction(ar[n]._interopCookie);
        ar[n].Dispose();
      }
    }
  }
}