Creating a zoom factor extension that works with a ToolbarControl
Application\ToolbarControlExtension.vb
' Copyright 2010 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.
' 

Option Strict Off
Option Explicit On

Imports ESRI.ArcGIS.esriSystem
Imports ESRI.ArcGIS.SystemUI
Imports ESRI.ArcGIS


Friend Class Form1
    Inherits System.Windows.Forms.Form
    <STAThread()> _
    Shared Sub Main()

        'Load runtime 
        If Not RuntimeManager.Bind(ProductCode.Engine) Then
            If Not RuntimeManager.Bind(ProductCode.Desktop) Then
                MessageBox.Show("Unable to bind to ArcGIS runtime. Application will be shut down.")
                System.Environment.Exit(1) ' Force exit or other indication in the application
            End If
        End If

        Application.Run(New Form1())
    End Sub
#Region "Windows Form Designer generated code "
    Public Sub New()
        MyBase.New()
        'This call is required by the Windows Form Designer.
        InitializeComponent()
    End Sub
    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal Disposing As Boolean)

        If Disposing Then
            If Not components Is Nothing Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(Disposing)
    End Sub
    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer
    Public WithEvents chkExtension As System.Windows.Forms.CheckBox
    Public WithEvents Label3 As System.Windows.Forms.Label
    Public WithEvents Label1 As System.Windows.Forms.Label
    Public WithEvents Label2 As System.Windows.Forms.Label
    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.
    'Do not modify it using the code editor.
    Friend WithEvents AxToolbarControl1 As ESRI.ArcGIS.Controls.AxToolbarControl
    Friend WithEvents AxMapControl1 As ESRI.ArcGIS.Controls.AxMapControl
    Friend WithEvents AxLicenseControl1 As ESRI.ArcGIS.Controls.AxLicenseControl
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Dim resources As System.ComponentModel.ComponentResourceManager = New System.ComponentModel.ComponentResourceManager(GetType(Form1))
        Me.chkExtension = New System.Windows.Forms.CheckBox
        Me.Label3 = New System.Windows.Forms.Label
        Me.Label1 = New System.Windows.Forms.Label
        Me.Label2 = New System.Windows.Forms.Label
        Me.AxToolbarControl1 = New ESRI.ArcGIS.Controls.AxToolbarControl
        Me.AxMapControl1 = New ESRI.ArcGIS.Controls.AxMapControl
        Me.AxLicenseControl1 = New ESRI.ArcGIS.Controls.AxLicenseControl
        CType(Me.AxToolbarControl1, System.ComponentModel.ISupportInitialize).BeginInit()
        CType(Me.AxMapControl1, System.ComponentModel.ISupportInitialize).BeginInit()
        CType(Me.AxLicenseControl1, System.ComponentModel.ISupportInitialize).BeginInit()
        Me.SuspendLayout()
        '
        'chkExtension
        '
        Me.chkExtension.BackColor = System.Drawing.SystemColors.Control
        Me.chkExtension.Cursor = System.Windows.Forms.Cursors.Default
        Me.chkExtension.Font = New System.Drawing.Font("Arial", 8.0!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.chkExtension.ForeColor = System.Drawing.SystemColors.ControlText
        Me.chkExtension.Location = New System.Drawing.Point(592, 8)
        Me.chkExtension.Name = "chkExtension"
        Me.chkExtension.RightToLeft = System.Windows.Forms.RightToLeft.No
        Me.chkExtension.Size = New System.Drawing.Size(113, 25)
        Me.chkExtension.TabIndex = 2
        Me.chkExtension.Text = "Enable Extension"
        Me.chkExtension.UseVisualStyleBackColor = False
        '
        'Label3
        '
        Me.Label3.BackColor = System.Drawing.SystemColors.Control
        Me.Label3.Cursor = System.Windows.Forms.Cursors.Default
        Me.Label3.Font = New System.Drawing.Font("Arial", 8.0!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label3.ForeColor = System.Drawing.SystemColors.ControlText
        Me.Label3.Location = New System.Drawing.Point(592, 136)
        Me.Label3.Name = "Label3"
        Me.Label3.RightToLeft = System.Windows.Forms.RightToLeft.No
        Me.Label3.Size = New System.Drawing.Size(137, 65)
        Me.Label3.TabIndex = 5
        Me.Label3.Text = "Enable the extension and navigate around the data using the commands from the ext" & _
            "ension."
        '
        'Label1
        '
        Me.Label1.BackColor = System.Drawing.SystemColors.Control
        Me.Label1.Cursor = System.Windows.Forms.Cursors.Default
        Me.Label1.Font = New System.Drawing.Font("Arial", 8.0!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label1.ForeColor = System.Drawing.SystemColors.ControlText
        Me.Label1.Location = New System.Drawing.Point(592, 88)
        Me.Label1.Name = "Label1"
        Me.Label1.RightToLeft = System.Windows.Forms.RightToLeft.No
        Me.Label1.Size = New System.Drawing.Size(137, 41)
        Me.Label1.TabIndex = 4
        Me.Label1.Text = "Navigate around the data using the commands on the ToolbarControl."
        '
        'Label2
        '
        Me.Label2.BackColor = System.Drawing.SystemColors.Control
        Me.Label2.Cursor = System.Windows.Forms.Cursors.Default
        Me.Label2.Font = New System.Drawing.Font("Arial", 8.0!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label2.ForeColor = System.Drawing.SystemColors.ControlText
        Me.Label2.Location = New System.Drawing.Point(592, 40)
        Me.Label2.Name = "Label2"
        Me.Label2.RightToLeft = System.Windows.Forms.RightToLeft.No
        Me.Label2.Size = New System.Drawing.Size(137, 40)
        Me.Label2.TabIndex = 3
        Me.Label2.Text = "Browse to a map document to load into the MapControl."
        '
        'AxToolbarControl1
        '
        Me.AxToolbarControl1.Location = New System.Drawing.Point(8, 8)
        Me.AxToolbarControl1.Name = "AxToolbarControl1"
        Me.AxToolbarControl1.OcxState = CType(resources.GetObject("AxToolbarControl1.OcxState"), System.Windows.Forms.AxHost.State)
        Me.AxToolbarControl1.Size = New System.Drawing.Size(576, 28)
        Me.AxToolbarControl1.TabIndex = 6
        '
        'AxMapControl1
        '
        Me.AxMapControl1.Location = New System.Drawing.Point(8, 40)
        Me.AxMapControl1.Name = "AxMapControl1"
        Me.AxMapControl1.OcxState = CType(resources.GetObject("AxMapControl1.OcxState"), System.Windows.Forms.AxHost.State)
        Me.AxMapControl1.Size = New System.Drawing.Size(576, 384)
        Me.AxMapControl1.TabIndex = 7
        '
        'AxLicenseControl1
        '
        Me.AxLicenseControl1.Enabled = True
        Me.AxLicenseControl1.Location = New System.Drawing.Point(595, 204)
        Me.AxLicenseControl1.Name = "AxLicenseControl1"
        Me.AxLicenseControl1.OcxState = CType(resources.GetObject("AxLicenseControl1.OcxState"), System.Windows.Forms.AxHost.State)
        Me.AxLicenseControl1.Size = New System.Drawing.Size(32, 32)
        Me.AxLicenseControl1.TabIndex = 8
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.BackColor = System.Drawing.SystemColors.Control
        Me.ClientSize = New System.Drawing.Size(731, 434)
        Me.Controls.Add(Me.AxLicenseControl1)
        Me.Controls.Add(Me.AxMapControl1)
        Me.Controls.Add(Me.AxToolbarControl1)
        Me.Controls.Add(Me.chkExtension)
        Me.Controls.Add(Me.Label3)
        Me.Controls.Add(Me.Label1)
        Me.Controls.Add(Me.Label2)
        Me.Cursor = System.Windows.Forms.Cursors.Default
        Me.Font = New System.Drawing.Font("Arial", 8.0!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Location = New System.Drawing.Point(4, 23)
        Me.Name = "Form1"
        Me.RightToLeft = System.Windows.Forms.RightToLeft.No
        Me.Text = "ZoomFactor Extension"
        CType(Me.AxToolbarControl1, System.ComponentModel.ISupportInitialize).EndInit()
        CType(Me.AxMapControl1, System.ComponentModel.ISupportInitialize).EndInit()
        CType(Me.AxLicenseControl1, System.ComponentModel.ISupportInitialize).EndInit()
        Me.ResumeLayout(False)

    End Sub
#End Region

    Private m_pExtensionManagerAdmin As IExtensionManagerAdmin

    Private Sub Form1_Load(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles MyBase.Load

        'Set buddy control
        AxToolbarControl1.SetBuddyControl(AxMapControl1.Object)

        'Add control command items to the ToolbarControl
        AxToolbarControl1.AddItem("esriControls.ControlsOpenDocCommand", -1, -1, False, 0, esriCommandStyles.esriCommandStyleIconOnly)
        AxToolbarControl1.AddItem("esriControls.ControlsMapZoomInTool", -1, -1, True, 0, esriCommandStyles.esriCommandStyleIconOnly)
        AxToolbarControl1.AddItem("esriControls.ControlsMapZoomOutTool", -1, -1, False, 0, esriCommandStyles.esriCommandStyleIconOnly)
        AxToolbarControl1.AddItem("esriControls.ControlsMapPanTool", -1, -1, False, 0, esriCommandStyles.esriCommandStyleIconOnly)
        'Add extension command items to the ToolbarControl
        AxToolbarControl1.AddItem("ZoomFactorExtensionVBNet.SetZoomFactor", -1, -1, True, 0, esriCommandStyles.esriCommandStyleIconAndText)
        AxToolbarControl1.AddItem("ZoomFactorExtensionVBNet.ZoomIn", -1, -1, False, 0, esriCommandStyles.esriCommandStyleIconAndText)
        AxToolbarControl1.AddItem("ZoomFactorExtensionVBNet.ZoomOut", -1, -1, False, 0, esriCommandStyles.esriCommandStyleIconAndText)

        'Get the extension manager admin
        m_pExtensionManagerAdmin = New ExtensionManagerClass

        'Add the extension to the extension manager
        Dim pUID As New UIDClass
        pUID.Value = "ZoomFactorExtensionVBNet.ZoomExtension"
        Call m_pExtensionManagerAdmin.AddExtension(pUID, 0)

    End Sub

    Private Sub chkExtension_CheckStateChanged(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles chkExtension.CheckStateChanged

        'Get the extension manager
        Dim pExtensionManager As IExtensionManager
        pExtensionManager = m_pExtensionManagerAdmin
        'Get the extension from the extension manager
        Dim pExtensionConfig As IExtensionConfig
        pExtensionConfig = pExtensionManager.FindExtension("Zoom Factor Extension")
        'Set the enabled state
        If (chkExtension.CheckState) Then
            pExtensionConfig.State = esriExtensionState.esriESEnabled
        Else
            pExtensionConfig.State = esriExtensionState.esriESDisabled
        End If

    End Sub

End Class