程序主界面如下图所示：

主界面代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.DataSourcesFile;
using ESRI.ArcGIS.DataSourcesGDB;
using ESRI.ArcGIS.Display;
using ESRI.ArcGIS.esriSystem;
using ESRI.ArcGIS.Geodatabase;
using ESRI.ArcGIS.Geometry;
using ESRI.ArcGIS.Output;
using ESRI.ArcGIS.SystemUI;

namespace WindowsFormsApplication1
{
    
    public partial class FrmMain : DevComponents.DotNetBar.RibbonForm
    {
    
        private INorthArrow m_NorthArrrow;
        private IElement m_Element;
        private string operation;

        // 构造函数
        public FrmMain()
        {
    
            InitializeComponent();
        }

        // 地图放大
        private void btnZoomIn_Click(object sender, EventArgs e)
        {
    
            operation = null;
            ICommand command = new ControlsPageZoomInTool();
            command.OnCreate(axPageLayoutControl1.Object);
            axPageLayoutControl1.CurrentTool = command as ITool;
        }

        // 地图缩小
        private void btnZoomOut_Click(object sender, EventArgs e)
        {
    
            operation = null;
            ICommand command = new ControlsPageZoomOutTool();
            command.OnCreate(axPageLayoutControl1.Object);
            axPageLayoutControl1.CurrentTool = command as ITool;
        }

        // 地图漫游
        private void btnPan_Click(object sender, EventArgs e)
        {
    
            operation = null;
            ICommand command = new ControlsPagePanTool();
            command.OnCreate(axPageLayoutControl1.Object);
            axPageLayoutControl1.CurrentTool = command as ITool;
        }

        // 全图显示
        private void btnFullExtent_Click(object sender, EventArgs e)
        {
    
            ICommand command = new ControlsPageZoomWholePageCommand();
            command.OnCreate(axPageLayoutControl1.Object);
            command.OnClick();
        }

        // 添加数据
        private void btnLoadData_Click(object sender, EventArgs e)
        {
    
            ICommand command = new ControlsAddDataCommand();
            command.OnCreate(axPageLayoutControl1.Object);
            command.OnClick();
        }

        // 添加指北针
        private void btnAddNorthArrow_Click(object sender, EventArgs e)
        {
    
            FrmNorthArrow frmNorthArrow = new FrmNorthArrow();
            frmNorthArrow.OnQueryNorthArrow += pNorthArrow => m_NorthArrrow = pNorthArrow;
            frmNorthArrow.ShowDialog();

            axPageLayoutControl1.CurrentTool = null;
            axPageLayoutControl1.MousePointer = esriControlsMousePointer.esriPointerCrosshair;
            operation = "添加指北针";
        }

        // OnMouseDown事件
        private void axPageLayoutControl1_OnMouseDown(object sender, IPageLayoutControlEvents_OnMouseDownEvent e)
        {
    
            if (operation == "添加指北针")
            {
    
                IEnvelope pEnvelope = axPageLayoutControl1.TrackRectangle();
                if (pEnvelope.IsEmpty || pEnvelope == null || pEnvelope.Width == 0 || pEnvelope.Height == 0)
                {
    
                    return;
                }

                // 删除已有指北针
                IActiveView pActiveViewv = axPageLayoutControl1.PageLayout as IActiveView;
                IGraphicsContainer pGraphicsContainer = pActiveViewv.GraphicsContainer;
                if (m_Element != null)
                {
    
                    pGraphicsContainer.DeleteElement(m_Element);
                    pActiveViewv.Refresh();
                }

                // 获取框架元素
                IMapFrame pMapFrame = pGraphicsContainer.FindFrame(pActiveViewv.FocusMap) as IMapFrame;
                IMapSurroundFrame pMapSurroundFrame = new MapSurroundFrame() as IMapSurroundFrame;
                pMapSurroundFrame.MapFrame = pMapFrame;
                pMapSurroundFrame.MapSurround = m_NorthArrrow as IMapSurround;

                // 添加指北针
                m_Element = pMapSurroundFrame as IElement;
                m_Element.Geometry = pEnvelope;
                pGraphicsContainer.AddElement(m_Element, 0);
                pActiveViewv.PartialRefresh(esriViewDrawPhase.esriViewGraphics, null, null);
            }
        }
    }
}

添加指北针界面如下图所示：
指北针界面代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using stdole;
using ESRI.ArcGIS.ADF;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.DataSourcesFile;
using ESRI.ArcGIS.DataSourcesGDB;
using ESRI.ArcGIS.Display;
using ESRI.ArcGIS.esriSystem;
using ESRI.ArcGIS.Geodatabase;
using ESRI.ArcGIS.Geometry;
using ESRI.ArcGIS.Output;
using ESRI.ArcGIS.SystemUI;

namespace WindowsFormsApplication1
{
    
    public partial class FrmNorthArrow : DevComponents.DotNetBar.OfficeForm
    {
    
        // 定义事件
        public event Action<INorthArrow> OnQueryNorthArrow;

        // 样式变量
        private ISymbologyStyleClass m_SymbologyStyleClass;
        private IStyleGalleryItem m_StyleGalleryItem;
        private INorthArrow m_NorthArrow;

        // 构造函数
        public FrmNorthArrow()
        {
    
            InitializeComponent();
        }

        // Load事件
        private void FrmNorthArrow_Load(object sender, EventArgs e)
        {
    
            axSymbologyControl1.LoadStyleFile(Application.StartupPath + "\\style\\ESRI.ServerStyle");
            axSymbologyControl1.StyleClass = esriSymbologyStyleClass.esriStyleClassNorthArrows;

            // 选择符号
            m_SymbologyStyleClass = axSymbologyControl1.GetStyleClass(axSymbologyControl1.StyleClass);
            m_SymbologyStyleClass.SelectItem(0);

            // 预览符号
            PriviewSymbol();
            inputAngle.Value = (int)m_NorthArrow.CalibrationAngle;
            inputColor.SelectedColor = Utility.ConvertToColor(m_NorthArrow.Color);
        }

        // 切换符号
        private void axSymbologyControl1_OnItemSelected(object sender, ISymbologyControlEvents_OnItemSelectedEvent e)
        {
    
            m_StyleGalleryItem = e.styleGalleryItem as IStyleGalleryItem;
            m_NorthArrow = m_StyleGalleryItem.Item as INorthArrow;

            // 
            PriviewSymbol();
            inputAngle.Value = (int)m_NorthArrow.CalibrationAngle;
            inputColor.SelectedColor = Utility.ConvertToColor(m_NorthArrow.Color);
        }

        // 设置颜色
        private void inputColor_SelectedColorChanged(object sender, EventArgs e)
        {
    
            m_NorthArrow.Color = Utility.ConvertToRgbColor(inputColor.SelectedColor);
            PriviewSymbol();
        }

        // 设置角度
        private void inputAngle_ValueChanged(object sender, EventArgs e)
        {
    
            m_NorthArrow.CalibrationAngle = inputAngle.Value;
            PriviewSymbol();
        }

        // 符号预览 
        private void PriviewSymbol()
        {
    
            IPictureDisp pPictureDisp = m_SymbologyStyleClass.PreviewItem(m_StyleGalleryItem, pictureBox1.Width, pictureBox1.Height);
            Image priviewImage = Image.FromHbitmap(new IntPtr(pPictureDisp.Handle));
            pictureBox1.Image = priviewImage;
        }

        // 确定
        private void btnOk_Click(object sender, EventArgs e)
        {
    
            if (OnQueryNorthArrow != null)
            {
    
                m_NorthArrow.Size *= 3;
                OnQueryNorthArrow(m_NorthArrow);
                this.Close();
                this.Dispose();
            }
        }

        // 取消
        private void btnCancel_Click(object sender, EventArgs e)
        {
    
            this.Close();
            this.Dispose();
        }
    }
}

辅助类代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using stdole;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.DataSourcesFile;
using ESRI.ArcGIS.DataSourcesGDB;
using ESRI.ArcGIS.Display;
using ESRI.ArcGIS.esriSystem;
using ESRI.ArcGIS.Geodatabase;
using ESRI.ArcGIS.Geometry;
using ESRI.ArcGIS.Output;
using ESRI.ArcGIS.SystemUI;

namespace WindowsFormsApplication1
{
    
    public class Utility
    {
    
        // Color转换为IColor
        public static IColor ConvertToRgbColor(Color color)
        {
    
            IColor pColor = new RgbColor();
            pColor.RGB = color.R + color.G * 256 + color.B * 65536;
            return pColor;
        }

        // IColor转换为Color
        public static Color ConvertToColor(IColor pColor)
        {
    
            return ColorTranslator.FromOle(pColor.RGB);
        }
    }
}

运行结果如下图：