Safe design pattern for creating and closing COM interop instances + support e.g. MS Office/Excel/Word/Powerpoint Interop without Microsoft's interop assemblies + access to COM object's public members with Reflection (instead of late binding (which often fails))
COM interop library with safe design pattern for COM instancing
When you need this COM interop library
COM interop often requires platform additional assemblies with platform dependency for Windows 32/64 bit
Microsoft Office development for Word/Excel/Powerpoint/etc. usualy requires you to add Microsoft's interop assemblies
Microsoft's interop assemblies often cause problems on client machines if there is another MS Office version installed than on the developer's machine
You just want to distribute your little small program to the clients regardless to their installed MS Office version
COM interop is often implented wrongly, causing MS Word/Excel/... to stay as process until your application terminates
Usually the application closes successfully if all COM objects have been closed and finalized correctly
Unfortunately, the .NET garbage collector can't do it automatically while your application is running
there is the need for finalizing all COM objects on dispose
After you created your COM instance e.g. with CreateObject("Excel.Application"), .NET isn't able to call many methods/properties/fields on COM objects using LateBinding, e.g. MsExcelAppViaCom.Quit()
This nice assembly provides these features
Access to public fields/properties/methods/function using System.Reflection (which allows calling of MsExcelAppViaCom.Quit() again)
Provide a base class for your custom implementations to access all required fields/properties/methods/function from your application as simple as possible
The base class comes with
an implementation for the IDisposable interface to dispose/finalize all COM objects incl. their children COM objects correctly
a design pattern which forces the developer to wrap all COM objects into classes inheriting from this base class
BUT: this assembly does NOT provide
features to run COM remoting on non-Windows platforms
<details>
<summary>First code impressions from https://www.github.com/CompuMasterGmbH/CompuMaster.Excel/</summary>
</details>
ExcelApplication
Public Class ExcelApplication
Inherits ComObjectBase
Public Sub New()
MyBase.New(Nothing, CreateObject("Excel.Application"))
Me.Workbooks = New ExcelWorkbooksCollection(Me, Me)
End Sub
Public ReadOnly Property Workbooks As ExcelWorkbooksCollection
Public Property UserControl As Boolean
Get
Return InvokePropertyGet(Of Boolean)("UserControl")
End Get
Set(value As Boolean)
InvokePropertySet("UserControl", value)
End Set
End Property
Public Property DisplayAlerts As Boolean
Get
Return InvokePropertyGet(Of Boolean)("DisplayAlerts")
End Get
Set(value As Boolean)
InvokePropertySet("DisplayAlerts", value)
End Set
End Property
Public Property Visible As Boolean
Get
Return InvokePropertyGet(Of Boolean)("Visible")
End Get
Set(value As Boolean)
InvokePropertySet("Visible", value)
End Set
End Property
Public Function Dialogs(type As Enumerations.XlBuiltInDialog) As ExcelDialog
Return New ExcelDialog(Me, InvokePropertyGet("Dialogs", CType(type, Integer)))
End Function
Public Function Run(vbaMethodNameInclWorkbookName As String) As Object
Return InvokeFunction("Run", New Object() {vbaMethodNameInclWorkbookName})
End Function
Public Function Run(workbookName As String, vbaMethod As String) As Object
Return InvokeFunction("Run", New Object() {"'" & workbookName & "'!" & vbaMethod})
End Function
Public ReadOnly Property IsClosed As Boolean
Get
Return MyBase.IsDisposedComObject
End Get
End Property
Public Sub Close()
Me.Quit()
End Sub
Public Sub Quit()
If Not IsDisposedComObject Then
UserControl = True
MyBase.CloseAndDisposeChildrenAndComObject()
End If
End Sub
Private AdditionalDisposeChildrenList As New List(Of ComObjectBase)
Protected Overrides Sub OnDisposeChildren()
If Me.Workbooks IsNot Nothing Then Me.Workbooks.Dispose()
End Sub
Protected Overrides Sub OnClosing()
InvokeMethod("Quit")
End Sub
Protected Overrides Sub OnClosed()
GC.Collect(2, GCCollectionMode.Forced, True)
End Sub
End Class
Excel WorkboksCollection
Public Class ExcelWorkbooksCollection
Inherits ComObjectBase
Friend Sub New(parentItemResponsibleForDisposal As ComObjectBase, app As ExcelApplication)
MyBase.New(parentItemResponsibleForDisposal, app.InvokePropertyGet("Workbooks"))
Me.Parent = app
End Sub
Friend ReadOnly Parent As ExcelApplication
Public Workbooks As New List(Of ExcelWorkbook)
Public Function Open(path As String) As ExcelWorkbook
Dim wb As New ExcelWorkbook(Me, Me, path)
Me.Workbooks.Add(wb)
Return wb
End Function
Protected Overrides Sub OnDisposeChildren()
For MyCounter As Integer = Workbooks.Count - 1 To 0 Step -1
Workbooks(MyCounter).Dispose()
Next
End Sub
Protected Overrides Sub OnClosing()
End Sub
Protected Overrides Sub OnClosed()
End Sub
End Class
Your custom COM class
Usualy provides for your custom implementation
Quit/Close application/document and dispose/finalize related COM objects
base.CloseAndDisposeChildrenAndComObject()
Invoke members of COM object by Reflection (instead of late binding) with several overloads of
base.Invoke...
Direct access to the COM object
base.ComObject
Status information on Com object if in-use vs. closed/disposed
base.IsDisposedComObject
Usualy requires you to implement
constructor method (Sub New in VisualBasic)
OnDisposeChildren()
Close and dispose commands for children objects
OnClosing()
Required close commands for the COM object like App.Quit() or Document.Close()
OnClosed()
Required actions after the COM object has been closed, e.g. removing from a list of open documents
Examples
COM application wrapper for Microsoft Excel Interop
//An application wrapper class for safe COM object handling and release for COM servers,
//properly releasing the COM object
//forcefully killing the application process on end if required
var ExcelEngine = new CompuMaster.ComInterop.ComApplication<Microsoft.Office.Interop.Excel.Application>(
new Microsoft.Office.Interop.Excel.Application,
(x) => x.ComObjectStronglyTyped.Hwnd,
(x) => x.ComObjectStronglyTyped.Quit(),
"EXCEL");
//do some nice things...
//quit (if you don't run Dispose method manually here, the garbage collector will do the job automatically to the given time)
ExcelEngine.Dispose();
COM application wrapper for Microsoft Excel completely without Interop assemblies/classes
//An application wrapper class for safe COM object handling and release for COM servers,
//forcefully killing the application process on end if required
var ExcelEngine = new CompuMaster.ComInterop.ComApplication<Object>(
"Excel.Application",
(x) => x.InvokePropertyGet<Int32>("Hwnd"),
(x) => x.InvokeMethod("Quit"),
"EXCEL");
//do some nice things...
//quit (if you don't run Dispose method manually here, the garbage collector will do the job automatically to the given time)
ExcelEngine.Dispose();