Creating workspace extensions

In this topic

• Common uses for workspace extensions
• Geodatabase registration vs. component category registration
  • Viewing a geodatabase's extensions
  • Geodatabase registration and unregistration
  • Component category registration and unregistration
• Adding the required attributes
• Implementing required and optional interfaces
  • IWorkspaceExtensionControl
  • IWorkspaceExtension and IWorkspaceExtension2
  • Optional interfaces

Common uses for workspace extensions

• Hiding datasets from workspace users. This is a common requirement for application specific data dictionary tables that users should not have access to; use IWorkspaceExtension and IWorkspaceExtension2 for this.
• Defining events that should occur when a user opens or disposes of a workspace; use IWorkspaceExtensionControl to define this behavior.
• Handling dataset creation, deletion, and modification events. This is done by implementing the IWorkspaceEvents optional interface.
• Handling workspace edit events, such as the start and stop of edit sessions and operations. This is done by implementing the IWorkspaceEditEvents optional interface.
• Handling versioning events, such as reconciliation or the detection of conflicts. This is done by implementing the IVersionEvents and IVersionEvents2 optional interfaces.
• Handling replication events, such as the beginning of replication and the completion of replication. This is done by implementing the IWorkspaceReplicaEvents optional interface.
• User-defined interfaces can be implemented by a workspace extension. This is a useful place to implement behavior or store data that affects the geodatabase as a whole.
  

Geodatabase registration vs. component category registration

Viewing a geodatabase's extensions

public void ListWorkspaceExtensions(IWorkspace workspace)
{
    // Cast the workspace to the IWorkspaceExtensionManager and loop through 
    // its extensions.
    IWorkspaceExtensionManager extensionManager=(IWorkspaceExtensionManager)
        workspace;
    for (int i=0; i < extensionManager.ExtensionCount; i++)
    {
        IWorkspaceExtension extension=extensionManager.get_Extension(i);
        UID extensionUID=extension.GUID;
        Console.WriteLine("Name: {0} - UID: {1}", extension.Name, extensionUID.Value)
            ;
    }
}

Public Sub ListWorkspaceExtensions(ByVal workspace As IWorkspace)
    ' Cast the workspace to the IWorkspaceExtensionManager and loop through
    ' its extensions.
    Dim extensionManager As IWorkspaceExtensionManager=CType(workspace, IWorkspaceExtensionManager)
    Dim i As Integer
    For i=0 To extensionManager.ExtensionCount - 1
        Dim extension As IWorkspaceExtension=extensionManager.Extension(i)
        Dim extensionUID As UID=extension.GUID
        Console.WriteLine("Name: {0} - UID: {1}", extension.Name, extensionUID.Value)
    Next i
End Sub

Geodatabase registration and unregistration

// For example, extensionName="ConnectLog.ConnectLogWorkspaceExtension".
// extensionUID="{d10a65c7-9257-4902-bd23-e666537bce01}".
public void RegisterWorkspaceExtension(IWorkspace workspace, String extensionName,
    String extensionUID)
{
    // Create a unique identifier (UID) object for the extension.
    UID uid=new UIDClass();
    uid.Value=extensionUID;

    // Cast the workspace to the IWorkspaceExtensionManager interface.
    IWorkspaceExtensionManager extensionManager=(IWorkspaceExtensionManager)
        workspace;

    // Try to register the extension.
    try
    {
        extensionManager.RegisterExtension(extensionName, uid);
    }
    catch (COMException comExc)
    {
        // TODO: Handle the exception in a way appropriate to your application.
    }
}

' For example, extensionName="ConnectLog.ConnectLogWorkspaceExtension".
' extensionUID="{d10a65c7-9257-4902-bd23-e666537bce01}".

Public Sub RegisterWorkspaceExtension(ByVal workspace As IWorkspace, ByVal extensionName As String, ByVal extensionUID As String)
    ' Create a unique identifier (UID) object for the extension.
    Dim uid As UID=New UIDClass()
    uid.Value=extensionUID
    
    ' Cast the workspace to the IWorkspaceExtensionManager interface.
    Dim extensionManager As IWorkspaceExtensionManager=CType(workspace, IWorkspaceExtensionManager)
    
    ' Try to register the extension.
    Try
    extensionManager.RegisterExtension(extensionName, uid)
    Catch comExc As COMException
    ' TODO: Handle the exception in a way appropriate to your application.
    End Try
End Sub

// For example, extensionUID="{d10a65c7-9257-4902-bd23-e666537bce01}".
public void UnregisterWorkspaceExtension(IWorkspace workspace, String extensionUID)
{
    // Create a UID object for the extension.
    UID uid=new UIDClass();
    uid.Value=extensionUID;

    // Cast the workspace to the IWorkspaceExtensionManager and unregister the extension.
    IWorkspaceExtensionManager extensionManager=(IWorkspaceExtensionManager)
        workspace;
    extensionManager.UnRegisterExtension(uid);
}

' For example, extensionUID="{d10a65c7-9257-4902-bd23-e666537bce01}".

Public Sub UnregisterWorkspaceExtension(ByVal workspace As IWorkspace, ByVal extensionUID As String)
    ' Create a UID object for the extension.
    Dim uid As UID=New UIDClass()
    UID.Value=extensionUID
    
    ' Cast the workspace to the IWorkspaceExtensionManager and unregister the extension.
    Dim extensionManager As IWorkspaceExtensionManager=CType(workspace, IWorkspaceExtensionManager)
    ExtensionManager.UnRegisterExtension(uid)
End Sub

Component category registration and unregistration

[ComRegisterFunction()][ComVisible(false)] static void RegisterFunction(Type
    registerType)
{
    string regKey=string.Format("HKEY_CLASSES_ROOT\\CLSID\\{{{0}}}",
        registerType.GUID);
    GeodatabaseWorkspaceExtensions.Register(regKey);
}

[ComUnregisterFunction()][ComVisible(false)] static void UnregisterFunction(Type
    registerType)
{
    string regKey=string.Format("HKEY_CLASSES_ROOT\\CLSID\\{{{0}}}",
        registerType.GUID);
    GeodatabaseWorkspaceExtensions.Unregister(regKey);
}

<ComRegisterFunction(), ComVisible(False)> _
                     Shared Sub RegisterFunction(ByVal registerType As Type)
    Dim regKey As String=String.Format("HKEY_CLASSES_ROOT\CLSID\{{{0}}}", registerType.GUID)
    GeodatabaseWorkspaceExtensions.Register(regKey)
End Sub

<ComUnregisterFunction(), ComVisible(False)> _
                       Shared Sub UnregisterFunction(ByVal registerType As Type)
    Dim regKey As String=String.Format("HKEY_CLASSES_ROOT\CLSID\{{{0}}}", registerType.GUID)
    GeodatabaseWorkspaceExtensions.Unregister(regKey)
End Sub

Adding the required attributes

• System.Runtime.InteropServices.GuidAttribute
• System.Runtime.InteropServices.ClassInterfaceAttribute
• System.Runtime.InteropServices.ProgIdAttribute

[Guid("d10a65c7-9257-4902-bd23-e666537bce01")][ClassInterface
    (ClassInterfaceType.None)][ProgId("ConnectLog.ConnectLogWorkspaceExtension")
    ][ComVisible(true)]
public class ConnectLogWorkspaceExtension: IWorkspaceExtension2,
    IWorkspaceExtensionControl
{
    // Class members here...
}

<Guid("d10a65c7-9257-4902-bd23-e666537bce01"), _
      ClassInterface(ClassInterfaceType.None), _
      ProgId("ConnectLog.ConnectLogWorkspaceExtension"), _
      ComVisible(True)> _
      Public Class ConnectLogWorkspaceExtension
    Implements IWorkspaceExtension2, IWorkspaceExtensionControl
    
    ' Class members here...
    
End Class

Implementing required and optional interfaces

• IWorkspaceEvents
• IWorkspaceEvents2 
• IWorkspaceEditEvents
• IWorkspaceEditEvents2
• IVersionEvents
• IVersionEvents2
• IWorkspaceReplicaEvents
• IWorkspaceReplicaSyncEvents

IWorkspaceExtensionControl

private IWorkspaceHelper workspaceHelper=null;

public void Init(IWorkspaceHelper workspaceHelper)
{
    // Set the private workspace helper field to the parameter.
    this.workspaceHelper=workspaceHelper;
}

Private workspaceHelper As IWorkspaceHelper=Nothing

Public Sub Init(ByVal workspaceHelper As IWorkspaceHelper) Implements IWorkspaceExtensionControl.Init
    ' Set the private workspace helper field to the parameter.
    Me.workspaceHelper=workspaceHelper
End Sub

public void Shutdown()
{
    workspaceHelper=null;
}

Public Sub Shutdown() Implements IWorkspaceExtensionControl.Shutdown
    workspaceHelper=Nothing
End Sub

IWorkspaceExtension and IWorkspaceExtension2

public String Name
{
    get
    {
        return "Connect Log Workspace Extension";
    }
}

public UID GUID
{
    get
    {
        UID uid=new UIDClass();
        uid.Value="{d10a65c7-9257-4902-bd23-e666537bce01}";
        return uid;
    }
}

Public ReadOnly Property Name() As String Implements IWorkspaceExtension.Name, IWorkspaceExtension2.Name
Get
Return "Connect Log Workspace Extension"
End Get
End Property

Public ReadOnly Property GUID() As UID Implements IWorkspaceExtension.GUID, IWorkspaceExtension2.GUID
Get
Dim uid As UID=New UIDClass()
uid.Value="{d10a65c7-9257-4902-bd23-e666537bce01}"
Return uid
End Get
End Property

• DataDictionaryTableNames returns an enumerator of table names that are used by the workspace extension to store application specific data. If none exists, null can be returned. 
• PrivateDatasetNames returns an enumerator of feature datasets, feature classes, relationship classes, and other datasets that are used internally by the workspace and should not be exposed to the user.

public IEnumBSTR DataDictionaryTableNames
{
    get
    {
        String[] hiddenTables=
        {
            "COUNTRY"
        };
        IEnumBSTR enumBSTR=new EnumBSTR(hiddenTables);
        return enumBSTR;
    }
}

Public ReadOnly Property DataDictionaryTableNames() As IEnumBSTR Implements IWorkspaceExtension.DataDictionaryTableNames, IWorkspaceExtension2.DataDictionaryTableNames
Get
Dim hiddenTables() As String=New String() {"COUNTRY"}
Dim enumBSTR As IEnumBSTR=New EnumBSTR(hiddenTables)
Return enumBSTR
End Get
End Property

public IWorkspace Workspace
{
    get
    {
        return workspaceHelper.Workspace;
    }
}

Public ReadOnly Property Workspace() As IWorkspace Implements IWorkspaceExtension2.Workspace
Get
Return workspaceHelper.Workspace
End Get
End Property

Optional interfaces

private const String logFile=@"C:\Temp\IWorkspaceEventsLog.txt";

public void OnCreateDataset(IDataset dataset)
{
    String createMessage="Dataset created: {0} At: {1}\n";
    String output=String.Format(createMessage, dataset.Name, DateTime.Now);
    File.AppendAllText(logFile, output);
}

public void OnDeleteDataset(IDataset dataset)
{
    String deleteMessage="Dataset deleted: {0} At: {1}\n";
    String output=String.Format(deleteMessage, dataset.Name, DateTime.Now);
    File.AppendAllText(logFile, output);
}

public void OnRenameDataset(IDataset dataset, String oldName, String newName)
{
    String renameMessage="Dataset renamed from: {0} to: {1} At: {2}\n";
    String output=String.Format(renameMessage, oldName, newName, DateTime.Now);
    File.AppendAllText(logFile, output);
}

Private Const logFile As String="C:\Temp\IWorkspaceEventsLog.txt"

Public Sub OnCreateDataset(ByVal dataset As IDataset) Implements IWorkspaceEvents.OnCreateDataset
    Dim createMessage As String="Dataset created: {0} At: {1}{2}"
    Dim output As String=String.Format(createMessage, dataset.Name, DateTime.Now, vbCrLf)
    File.AppendAllText(logFile, output)
End Sub

Public Sub OnDeleteDataset(ByVal dataset As IDataset) Implements IWorkspaceEvents.OnDeleteDataset
    Dim deleteMessage As String="Dataset deleted: {0} At: {1}{2}"
    Dim output As String=String.Format(deleteMessage, dataset.Name, DateTime.Now, vbCrLf)
    File.AppendAllText(logFile, output)
End Sub

Public Sub OnRenameDataset(ByVal dataset As IDataset, ByVal oldName As String, ByVal newName As String) Implements IWorkspaceEvents.OnRenameDataset
    Dim renameMessage As String="Dataset renamed from: {0} to: {1} At: {2}{3}"
    Dim output As String=String.Format(renameMessage, oldName, newName, DateTime.Now, vbCrLf)
    File.AppendAllText(logFile, output)
End Sub

See Also:

• ESRI.ArcGIS.ADF.Local
• ESRI.ArcGIS.System (ESRI.ArcGIS.esriSystem)
• ESRI.ArcGIS.Geodatabase