Add a custom menu created in .NET to ArcGIS for Desktop
AddShapefile.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 System.Windows.Forms
Imports ESRI.ArcGIS.Geodatabase
Imports ESRI.ArcGIS.DataSourcesFile
Imports ESRI.ArcGIS.Carto
Imports System.Runtime.InteropServices
Imports System.Drawing
Imports ESRI.ArcGIS.ADF.BaseClasses
Imports ESRI.ArcGIS.ADF.CATIDs
Imports ESRI.ArcGIS.Framework
Imports ESRI.ArcGIS.ArcMapUI

<ComClass(AddShapefile.ClassId, AddShapefile.InterfaceId, AddShapefile.EventsId), _
 ProgId("CustomMenus.AddShapefile")> _
Public NotInheritable Class AddShapefile
    Inherits BaseCommand

#Region "COM GUIDs"
    ' These  GUIDs provide the COM identity for this class 
    ' and its COM interfaces. If you change them, existing 
    ' clients will no longer be able to access the class.
    Public Const ClassId As String = "6f8f48fe-bfbc-4b2a-b1e7-25eced548743"
    Public Const InterfaceId As String = "8390d0e1-54f5-4ec3-b20f-3ff96f1f37f6"
    Public Const EventsId As String = "d87cda80-8257-4b7f-abb0-3c08d6b0ddde"
#End Region

#Region "COM Registration Function(s)"
    <ComRegisterFunction(), ComVisibleAttribute(False)> _
    Public Shared Sub RegisterFunction(ByVal registerType As Type)
        ' Required for ArcGIS Component Category Registrar support
        ArcGISCategoryRegistration(registerType)

        'Add any COM registration code after the ArcGISCategoryRegistration() call

    End Sub

    <ComUnregisterFunction(), ComVisibleAttribute(False)> _
    Public Shared Sub UnregisterFunction(ByVal registerType As Type)
        ' Required for ArcGIS Component Category Registrar support
        ArcGISCategoryUnregistration(registerType)

        'Add any COM unregistration code after the ArcGISCategoryUnregistration() call

    End Sub

#Region "ArcGIS Component Category Registrar generated code"
    Private Shared Sub ArcGISCategoryRegistration(ByVal registerType As Type)
        Dim regKey As String = String.Format("HKEY_CLASSES_ROOT\CLSID\{{{0}}}", registerType.GUID)
        MxCommands.Register(regKey)

    End Sub
    Private Shared Sub ArcGISCategoryUnregistration(ByVal registerType As Type)
        Dim regKey As String = String.Format("HKEY_CLASSES_ROOT\CLSID\{{{0}}}", registerType.GUID)
        MxCommands.Unregister(regKey)

    End Sub

#End Region
#End Region


    Private m_application As IApplication

    ' A creatable COM class must have a Public Sub New() 
    ' with no parameters, otherwise, the class will not be 
    ' registered in the COM registry and cannot be created 
    ' via CreateObject.
    Public Sub New()
        MyBase.New()

    MyBase.m_category = "Developer Samples"
    MyBase.m_caption = "Add Shapefile"
    MyBase.m_message = "Adds a shapefile to the focus map"
    MyBase.m_toolTip = "Add Shapefile"
    MyBase.m_name = "CustomMenus_AddShapefile"

        Try
      Dim bitmapResourceName As String = Me.GetType().Name + ".bmp"
      MyBase.m_bitmap = New Bitmap(Me.GetType(), bitmapResourceName)
    Catch ex As Exception
      System.Diagnostics.Trace.WriteLine(ex.Message, "Invalid Bitmap")
    End Try


    End Sub


    Public Overrides Sub OnCreate(ByVal hook As Object)
        If Not hook Is Nothing Then
            m_application = CType(hook, IApplication)

            'Disable if it is not ArcMap
            If TypeOf hook Is IMxApplication Then
                MyBase.m_enabled = True
            Else
                MyBase.m_enabled = False
            End If
        End If

  End Sub

  Public Overrides Sub OnClick()
    Dim mxDocument As IMxDocument = TryCast(m_application.Document, IMxDocument)
    AddShapefileUsingOpenFileDialog(mxDocument.ActiveView)
  End Sub


    '##### ArcGIS Snippets #####

#Region "Add Shapefile Using OpenFileDialog"
    ' ArcGIS Snippet Title:
    ' Add Shapefile Using OpenFileDialog
    ' 
    ' Long Description:
    ' Add a shapefile to the ActiveView using the Windows.Forms.OpenFileDialog control.
    ' 
    ' Add the following references to the project:
    ' ESRI.ArcGIS.Carto
    ' ESRI.ArcGIS.DataSourcesFile
    ' ESRI.ArcGIS.Geodatabase
    ' System.Windows.Forms
    ' 
    ' Intended ArcGIS Products for this snippet:
    ' ArcGIS Desktop (Standard, Advanced, Basic)
    ' ArcGIS Engine
    ' 
    ' Applicable ArcGIS Product Versions:
    ' 9.2
    ' 9.3
    ' 
    ' Required ArcGIS Extensions:
    ' (NONE)
    ' 
    ' Notes:
    ' This snippet is intended to be inserted at the base level of a Class.
    ' It is not intended to be nested within an existing Function or Sub.
    ' 

    '''<summary>Add a shapefile to the ActiveView using the Windows.Forms.OpenFileDialog control.</summary>
    '''
    '''<param name="activeView">An IActiveView interface</param>
    ''' 
    '''<remarks></remarks>
    Public Sub AddShapefileUsingOpenFileDialog(ByVal activeView As ESRI.ArcGIS.Carto.IActiveView)

        'parameter check
        If activeView Is Nothing Then

            Return

        End If

        ' Use the OpenFileDialog Class to choose which shapefile to load.
        Dim openFileDialog As System.Windows.Forms.OpenFileDialog = New System.Windows.Forms.OpenFileDialog
        openFileDialog.InitialDirectory = "c:\"
        openFileDialog.Filter = "Shapefiles (*.shp)|*.shp"
        openFileDialog.FilterIndex = 2
        openFileDialog.RestoreDirectory = True
        openFileDialog.Multiselect = False

        If openFileDialog.ShowDialog = System.Windows.Forms.DialogResult.OK Then

            ' The user chose a particular shapefile.

            ' The returned string will be the full path, filename and file-extension for the chosen shapefile. Example: "C:\test\cities.shp"
            Dim shapefileLocation As String = openFileDialog.FileName

            If shapefileLocation <> "" Then

                ' Ensure the user chooses a shapefile

                ' Create a new ShapefileWorkspaceFactory CoClass to create a new workspace
                Dim workspaceFactory As ESRI.ArcGIS.Geodatabase.IWorkspaceFactory = New ESRI.ArcGIS.DataSourcesFile.ShapefileWorkspaceFactoryClass

                ' System.IO.Path.GetDirectoryName(shapefileLocation) returns the directory part of the string. Example: "C:\test\"
                Dim featureWorkspace As ESRI.ArcGIS.Geodatabase.IFeatureWorkspace = CType(workspaceFactory.OpenFromFile(System.IO.Path.GetDirectoryName(shapefileLocation), 0), ESRI.ArcGIS.Geodatabase.IFeatureWorkspace) ' Explicit Cast

                ' System.IO.Path.GetFileNameWithoutExtension(shapefileLocation) returns the base filename (without extension). Example: "cities"
                Dim featureClass As ESRI.ArcGIS.Geodatabase.IFeatureClass = featureWorkspace.OpenFeatureClass(System.IO.Path.GetFileNameWithoutExtension(shapefileLocation))

                Dim featureLayer As ESRI.ArcGIS.Carto.IFeatureLayer = New ESRI.ArcGIS.Carto.FeatureLayerClass
                featureLayer.FeatureClass = featureClass
                featureLayer.Name = featureClass.AliasName
                featureLayer.Visible = True
                activeView.FocusMap.AddLayer(featureLayer)

                ' Zoom the display to the full extent of all layers in the map
                activeView.Extent = activeView.FullExtent
                activeView.PartialRefresh(ESRI.ArcGIS.Carto.esriViewDrawPhase.esriViewGeography, Nothing, Nothing)

            Else

                ' The user did not choose a shapefile.
                ' Do whatever remedial actions as necessary
                ' System.Windows.Forms.MessageBox.Show("No shapefile chosen", "No Choice #1", System.Windows.Forms.MessageBoxButtons.OK,  System.Windows.Forms.MessageBoxIcon.Exclamation)

            End If

        Else

            ' The user did not choose a shapefile. They clicked Cancel or closed the dialog by the "X" button.
            ' Do whatever remedial actions as necessary.
            ' System.Windows.Forms.MessageBox.Show("No shapefile chosen", "No Choice #2", System.Windows.Forms.MessageBoxButtons.OK, System.Windows.Forms.MessageBoxIcon.Exclamation)

        End If

    End Sub
#End Region

End Class