Add map surrounds using the SymbologyControl
CreateScaleText.cs
// Copyright 2012 ESRI
// 
// All rights reserved under the copyright laws of the United States
// and applicable international laws, treaties, and conventions.
// 
// You may freely redistribute and use this sample code, with or
// without modification, provided you include the original copyright
// notice and use restrictions.
// 
// See the use restrictions.
// 

using System;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.Display;
using ESRI.ArcGIS.Geometry;
using ESRI.ArcGIS.ADF.BaseClasses;
using ESRI.ArcGIS.ADF.CATIDs;
using System.Runtime.InteropServices;

namespace AddMapSurrounds
{
  [ClassInterface(ClassInterfaceType.None)]
  [Guid("283181EA-08F8-468f-A8FA-4ADEDC087C74")]

  public sealed class CreateScaleText : BaseTool
  {
    private IHookHelper m_HookHelper; 
    private INewEnvelopeFeedback m_Feedback;
    private IPoint m_Point; 
    private bool m_InUse;

    //Windows API functions to capture mouse and keyboard
    //input to a window when the mouse is outside the window
    [DllImport("User32", CharSet=CharSet.Auto)]
    private static extern int SetCapture(int hWnd);
    [DllImport("User32", CharSet=CharSet.Auto)]
    private static extern int GetCapture();
    [DllImport("User32", CharSet=CharSet.Auto)]
    private static extern int ReleaseCapture();

    #region Component Category Registration
    [ComRegisterFunction()]
    [ComVisible(false)]
    static void RegisterFunction(String sKey)
    {
      ControlsCommands.Register(sKey);
    }
    [ComUnregisterFunction()]
    [ComVisible(false)]
    static void UnregisterFunction(String sKey)
    {
      ControlsCommands.Unregister(sKey);
    }
    #endregion

    public CreateScaleText()
    {
        //Create an IHookHelper object
      m_HookHelper = new HookHelperClass();

      //Set the tool properties
      base.m_bitmap = new System.Drawing.Bitmap(GetType().Assembly.GetManifestResourceStream(GetType(), "ScaleText.bmp"));
      base.m_caption = "ScaleText";
      base.m_category = "myCustomCommands(C#)";
      base.m_message = "Add a scale text map surround";
      base.m_name = "myCustomCommands(C#)_ScaleText";
      base.m_toolTip = "Add a scale text";
      base.m_deactivate = true;
    }
  
    public override void OnCreate(object hook)
    {
      m_HookHelper.Hook = hook;
    }
  
    public override void OnMouseDown(int Button, int Shift, int X, int Y)
    {
      //Create a point in map coordinates
      m_Point = m_HookHelper.ActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(X, Y);

      //Start capturing mouse events
      SetCapture(m_HookHelper.ActiveView.ScreenDisplay.hWnd);

      m_InUse = true;  
    }
  
    public override void OnMouseMove(int Button, int Shift, int X, int Y)
    {
      if (m_InUse == false) return;

      //Start an envelope feedback
      if (m_Feedback == null )
      {
        m_Feedback = new NewEnvelopeFeedbackClass();
        m_Feedback.Display = m_HookHelper.ActiveView.ScreenDisplay;
        m_Feedback.Start(m_Point);
      }

      //Move the envelope feedback
      m_Feedback.MoveTo(m_HookHelper.ActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(X, Y));
    }
  
    public override void OnMouseUp(int Button, int Shift, int X, int Y)
    {
      if (m_InUse == false) return;

      //Stop capturing mouse events
      if (GetCapture() == m_HookHelper.ActiveView.ScreenDisplay.hWnd)
        ReleaseCapture();

      //If an envelope has not been tracked or its height/width is 0
      if (m_Feedback == null)
      {
        m_Feedback = null;
        m_InUse = false;
        return;
      }
      IEnvelope envelope = m_Feedback.Stop();
      if ((envelope.IsEmpty) || (envelope.Width == 0) || (envelope.Height == 0))
      {
        m_Feedback = null;
        m_InUse = false;
        return;
      }

      //Create the form with the SymbologyControl
      SymbolForm symbolForm = new SymbolForm();
      //Get the IStyleGalleryItem
      IStyleGalleryItem styleGalleryItem = symbolForm.GetItem(esriSymbologyStyleClass.esriStyleClassScaleTexts);
      //Release the form
      symbolForm.Dispose();
      if (styleGalleryItem == null) return;

      //Get the map frame of the focus map
      IMapFrame mapFrame = (IMapFrame) m_HookHelper.ActiveView.GraphicsContainer.FindFrame(m_HookHelper.ActiveView.FocusMap);

      //Create a map surround frame
      IMapSurroundFrame mapSurroundFrame = new MapSurroundFrameClass(); 
      //Set its map frame and map surround
      mapSurroundFrame.MapFrame = mapFrame;
      mapSurroundFrame.MapSurround = (IMapSurround) styleGalleryItem.Item;

      //QI to IElement and set its geometry
      IElement element = (IElement) mapSurroundFrame;
      element.Geometry = envelope;

      //Add the element to the graphics container
      m_HookHelper.ActiveView.GraphicsContainer.AddElement((IElement)mapSurroundFrame, 0);
      //Refresh
      m_HookHelper.ActiveView.PartialRefresh(esriViewDrawPhase.esriViewGraphics, mapSurroundFrame, null);

      m_Feedback = null;
      m_InUse = false;
    }
  }
}