Simple dynamic display application
MainForm.vb
' 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.
' 

Imports Microsoft.VisualBasic
Imports System
Imports System.Drawing
Imports System.Collections
Imports System.ComponentModel
Imports System.Windows.Forms
Imports System.Data
Imports System.IO
Imports System.Runtime.InteropServices

Imports ESRI.ArcGIS.esriSystem
Imports ESRI.ArcGIS.Carto
Imports ESRI.ArcGIS.Controls
Imports ESRI.ArcGIS.ADF
Imports ESRI.ArcGIS.SystemUI

  Public NotInheritable Partial Class MainForm : Inherits Form
  #Region "class private members"
  Private m_mapControl As IMapControl3 = Nothing
  Private m_mapDocumentName As String = String.Empty
  #End Region

  #Region "class constructor"
  Public Sub New()
    InitializeComponent()
  End Sub
  #End Region

  Private Sub MainForm_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
    'get the MapControl
    m_mapControl = CType(axMapControl1.Object, IMapControl3)

    'disable the Save menu (since there is no document yet)
    menuSaveDoc.Enabled = False

    axToolbarControl1.AddItem(New ToggleDynamicDisplayCmd())
    axToolbarControl1.AddItem(New LoadDynamicLayerCmd())
  End Sub

  #Region "Main Menu event handlers"
  Private Sub menuNewDoc_Click(ByVal sender As Object, ByVal e As EventArgs) Handles menuNewDoc.Click
    'execute New Document command
    Dim command As ICommand = New CreateNewDocument()
    command.OnCreate(m_mapControl.Object)
    command.OnClick()
  End Sub

  Private Sub menuOpenDoc_Click(ByVal sender As Object, ByVal e As EventArgs) Handles menuOpenDoc.Click
    'execute Open Document command
    Dim command As ICommand = New ControlsOpenDocCommandClass()
    command.OnCreate(m_mapControl.Object)
    command.OnClick()
  End Sub

  Private Sub menuSaveDoc_Click(ByVal sender As Object, ByVal e As EventArgs) Handles menuSaveDoc.Click
    'execute Save Document command
    If m_mapControl.CheckMxFile(m_mapDocumentName) Then
      'create a new instance of a MapDocument
      Dim mapDoc As IMapDocument = New MapDocumentClass()
      mapDoc.Open(m_mapDocumentName, String.Empty)

      'Make sure that the MapDocument is not readonly
      If mapDoc.IsReadOnly(m_mapDocumentName) Then
       MessageBox.Show("Map document is read only!")
        mapDoc.Close()
        Return
      End If

      'Replace its contents with the current map
      mapDoc.ReplaceContents(CType(m_mapControl.Map, IMxdContents))

      'save the MapDocument in order to persist it
      mapDoc.Save(mapDoc.UsesRelativePaths, False)

      'close the MapDocument
      mapDoc.Close()
    End If
  End Sub

  Private Sub menuSaveAs_Click(ByVal sender As Object, ByVal e As EventArgs) Handles menuSaveAs.Click
    'execute SaveAs Document command
    Dim command As ICommand = New ControlsSaveAsDocCommandClass()
    command.OnCreate(m_mapControl.Object)
    command.OnClick()
  End Sub

  Private Sub menuExitApp_Click(ByVal sender As Object, ByVal e As EventArgs) Handles menuExitApp.Click
    'exit the application
    Application.Exit()
  End Sub
  #End Region

    'listen to MapReplaced event in order to update the status bar and the Save menu
  Private Sub axMapControl1_OnMapReplaced(ByVal sender As Object, ByVal e As IMapControlEvents2_OnMapReplacedEvent) Handles axMapControl1.OnMapReplaced
    'get the current document name from the MapControl
    m_mapDocumentName = m_mapControl.DocumentFilename

        'if there is no MapDocument, disable the Save menu and clear the status bar
    If m_mapDocumentName = String.Empty Then
      menuSaveDoc.Enabled = False
      statusBarXY.Text = String.Empty
    Else
            'enable the Save menu and write the doc name to the status bar
      menuSaveDoc.Enabled = True
      statusBarXY.Text = Path.GetFileName(m_mapDocumentName)
    End If
  End Sub

  Private Sub axMapControl1_OnMouseMove(ByVal sender As Object, ByVal e As IMapControlEvents2_OnMouseMoveEvent) Handles axMapControl1.OnMouseMove
    statusBarXY.Text = String.Format("{0}, {1}  {2}", e.mapX.ToString("#######.##"), e.mapY.ToString("#######.##"), axMapControl1.MapUnits.ToString().Substring(4))
  End Sub
  End Class