.NET Tutorials, Forums, Interview Questions And Answers
Welcome :Guest
Sign In
Win Surprise Gifts!!!

Top 5 Contributors of the Month
david stephan
Gaurav Pal
Post New Web Links

Is it possible to cast COM object to the custom interface?

Posted By:      Posted Date: September 24, 2010    Points: 0   Category :.NET Framework

I have following code which succesfully works using some COM wrapper library with all needed managed types for COM objects

mshtml.HTMLDocumentClass doc = (mshtml.HTMLDocumentClass)_webBrowser.Document;

mshtml.HTMLIFrameClass iframe = (doc).getElementById("SomeFrameName") as mshtml.HTMLIFrameClass;

if (string.Equals(iframe.readyState.ToString(), "complete", StringComparison.OrdinalIgnoreCase))


 // Do something


But I need to avoid this COM wrapper Micrososft.mshtml.dll and use custom interfaces for this reason, so please explain me how way can I work with COM objects with custom interfaces? How do I write them and avoid classes mshtml.HTMLDocumentClass and mshtml.HTMLIFrameClass?

View Complete Post

More Related Resource Links

Unable to cast COM object of type 'System.__ComObject' to interface type 'IRowset'


Unable to cast COM object of type 'System.__ComObject' to interface type 'IRowset' in BIDS

I'm using BIDS for working with SSAS. I have bug with New Named Query feature.
Steps to reproduce:
1. Set up any data source.
2. Set up new data source view with any tables.
3. Right click on DSV body. Select 'New Named Query'
4. Switch to Generic Query Builder.
5. Type any query. For instance 'select name from sys.sysobjects'
6. Press Run button

After this message:
TITLE: Microsoft Visual Studio

An error occurred while reading data from the query result set.
Unable to cast COM object of type 'System.__ComObject' to interface type 'IRowset'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{0C733A7C-2A1C-11CE-ADE5-00AA0044773D}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).


Unable to cast COM object of type 'System.__ComObject' to interface type 'IRowset'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{0C733A7C-2A1C-11CE-ADE5-00AA0044773D}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)). (System.Data)


Fuzz Testing: Create a Custom Test Interface Provider for Team System


Dan Griffin shows the extensibility of Visual Studio 2005 Team Edition for Software Testers by discussing the modification of the existing Test Interface Provider sample in the latest Visual Studio SDK and implements Fuzz Testing.

Dan Griffin

MSDN Magazine November 2007

Contexts in .NET: Decouple Components by Injecting Custom Services into Your Object's Interception


The .NET Framework can use contexts as an object's execution scope and intercept calls going to and from the object, similar to the way COM+ provides component services. What is new with this mechanism is that the runtime allows developers to take part in the interception chain and add powerful services, thus extending existing component services. This in turn decouples the business logic from the system plumbing and simplifies long-term maintenance. Presently, .NET contexts and interception are undocumented aspects of .NET. This article presents the underlying interception architecture and message processing, explains custom context attributes, and walks through a custom interception-based component service.

Juval Lowy

MSDN Magazine March 2003

Building a Custom Data Grid: Performing Ad Hoc Web Reporting with a VBScript 5.0 Class Object


A flexible, customizable grid for displaying data is a useful tool for ASP developers. It allows Web visitors to customize their view of your data. This article takes the data grid presented in "Ad Hoc Web Reporting with ADO 2.0" by John Papa and Charles Caison (MIND, December 1998) and adds handy features such as a finds feature that supports multiple finds and a mode for adding and editing records. This version also improves response time by allowing asynchronous record download and it componentizes the code so it can be used as a standalone VBScript class object that can be reused in other pages.

Randall Kindig

MSDN Magazine July 2000

Unable to cast object of type 'System.Web.Mvc.ValueProviderResult' to type 'System.IConvertible'


 Why am I getting this error on line:

               sp.Price = Convert.ToDecimal(collection.GetValue("Price"));

sp is :
  SPecials_Templates sp = new SPecials_Templates();

SPecials_Templates Defined:

    public partial class SPecials_Templates
        public class SPecials_TemplatesMetaData

            public object Key { get; set; }
            public object Template_Name { get; set; }
            public object Headline { get; set; }

Large document libraries with a custom user interface


We recently migrated our document management system to SharePoint (WSS 3.0) and I adapted my VB6 client application to search for and retrieve a list of documents from this new SharePoint library using the Lists web service. Although the total number of documents in this library is 90,000 at one site and over 145,000 at another, my VB6 application never retrieves more than 600-700 documents at a time. From reading white papers such as "Working with Large Lists in Office SharePoint Server 2007" (http://go.microsoft.com/fwlink/?LinkId=95450&clcid=0x409), it appears that if my custom user interface limits the number of items returned in a search of these large lists, that it may not be necessary to put these documents into folders. However, our current scanning software, KnowledgeLake Capture, by default places newly scanned documents into folders based on the year, month, day and hour, which means that these documents are placed in nested folders 4 levels deep.

There are also some 20 metadata fields on these document libraries that allow us to filter these document libraries so that search results will in most cases be limited to a few hundred items.

We acquired new servers (Windows Server 2008 with SQL Server 2008) to host our SharePoint libraries and we are running WSS 3.0 S

Problem passing custom object returned by the same webservice among two separate projects

I am running into casting issue with this scenario: 1. I made a custom object lets call it EmployeeObject.  2. The Employee object is wrapped in the EmployeeWebservice.  3. I have a client application project lets call it EmployeeClientApplication and a class library called DoSomeWorkClassLibrary.  Both EmployeeClientApplication and DoSomeWorkClassLibrary reference the EmployeeWebService and need to be able to pass the EmployeeObject back and forth.  4. The EmployeeClientApplication also references the DoSomeWorkClassLibrary. 5. The employeeObject in the EmployeeClientApplication becomes EmployeeClientApplication.EmployeeWebService.EmployeeObject. 6. The employeeObject in the DoSomeWorkClassLibrary becomes DoSomeWorkClassLibrary.EmployeeWebService.EmployeeObject. 7. The DoSomeWorkClassLibrary has a method called DoSomeWork that takes an EmployeeObject. When I try to pass employeeObject from EmployeeClientApplication to DoSomeWorkClassLibrary by doing something like this: DoSomeWorkClassLibrary.DoSomeWork(EmployeeClientApplication.EmployeeWebService.EmployeeObject), I am getting Unable to convert EmployeeClientApplication.EmployeeWebService.EmployeeObject to DoSomeWorkClassLibrary.EmployeeWebService.EmployeeObject.  I have searched high and low to fix this issue, I have tried changing the namespace of the reference.cs file of the webservice in

Unable to Cast COM object

All, I receive this error when I tried to create SSIS project and add or create new SSIS package inside. Link to image as unable to insert here as directed in this link. Error:  Mircrosoft Visual Studio is unable to load this document: Unable to cast COM object of type 'Microsoft.SqlServer.Dts.Runtime.Wrapper.PackageNeutralClass' to interface type 'Microsoft.SqlServer.Dts.Runtime.Wrapper.IDTSPackageSigning100'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{A896D87C-D1B2-4FAE-9339-CFAFEFE617BE}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)) Possible Reason: 1. I was running on SQL Server 2008 R2 Evaluation Edition but I uninstall it and installed SQL Server 2008 Developer Edition with SP2 (CTP) first but when I see this problem so I uninstalled SP2 and now running on SQL Server 2008 with SP1. 2. I was also running on Visual Studio 2010 Professional Edition along with SQL 2008 R2 but I uninstall both same time when I installed SQL Server 2008 Dev edition. My OS is Windows XP SP3 and SQL Server 2008 SP1 as I mentioned.   I tried below steps but no luck  1. Registering DLL in this link. http://social.msdn.microsoft.com/forums/en-US/sqlintegrationservices/thread/7f5c9ae1-ecd3-4ead-98fd-2d074720e31d/ 2. Follow article

SP2010 Client Object Model: How to cast Field to FieldCalculated

Hello, I need to modify formula for existing field and can't do it because this code raise exception - (Cannot cast 'fld' (which has an actual type of 'Microsoft.SharePoint.Client.Field') to 'Microsoft.SharePoint.Client.FieldCalculated').   using (var clientContext = new ClientContext(@"http://Server")) { var web = clientContext.Web; var lst = web.Lists.GetByTitle("MyList"); <strong>var fld = (FieldCalculated)lst.Fields.GetByInternalNameOrTitle("Formula1");</strong> clientContext.Load(fld); clientContext.ExecuteQuery(); }   I can't use fld.SchemaXml modification by some reason. May be you can help me? Thank you.

Object cannot be cast from DBNull to other types

hello,i am using a web servicewrtitten in .net and i access the webservice from my wepApplication i get this error System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> Object cannot be cast from DBNull to other types.my code is access webservice: protected void btnSave_Click(object sender, EventArgs e)        {            int intStatusCode;            dtProjectStatus = (DataTable)ViewState["dtProjectStatus"];            try            {                objService.Credentials = System.Net.CredentialCache.DefaultCredentials;                if(dtProjectStatus.Rows.Count>0)                {                  intStatusCode = objService.InsertTest(dtProjectStatus);                }   

Object cannot be cast from DBNull to other types.

Object cannot be cast from DBNull to other types. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidCastException: Object cannot be cast from DBNull to other types.Source Error: Line 292: Line 293: If DataBinder.Eval(e.Row.DataItem, "Casette") IsNot Nothing Then Line 294: stcassette += Convert.ToDecimal(DataBinder.Eval(e.Row.DataItem, "Casette")) Line 295: End If Line 296:

Custom Object as the TreeViewItem

Hi, My work demands that I need to have an object stored in a treeviewitem. I tried doing it, but with no avail. It would be brilliant if somebody could throw some light on how to achieve this with minimum fuss. Cheery Krish  

Details View Biding Custom Object with Enum properties fields

Hello, I'm trying to bind custom object to details view. The problem is that enum property fields are not show.Is there any way to show enum property fields in details view ?I put some example code below (I do not specify any rows mappings, they are generated dynamically because different kind of objects are bound to details view):// My object public class OrderItem { public ItemKindEnum unitemizedItemKind { get { return (ItemKindEnum)this.unitemizedItemKindID; } } ... } // Details view configuration <asp:DetailsView ID="dvOperationDetails" runat="server" DefaultMode="ReadOnly" ... />

Multilingual Interface (Hindi) custom, webpart issue disappearance in share point 2007

Hi This is regarding the disappearance of custom  web parts in the multilingual site developed using MOSS 2007. The multilingual feature has been implemented using variations. All the custom web parts disappear when viewed after some time.  When the custom web parts are deployed to the site, it appears and they disappear when viewed after some time.  I have done local deployment as well as GAC deployment of the web parts dll. Both have the same effect. I have added the respective resource files for the web parts in the user control folder.    Thanks In Advance uttam  

Object cannot be cast from DBNull to other types

Case "System.Int32"                Return Convert.ToInt32(a) + Convert.ToInt32(b)Object cannot be cast from DBNull to other types
ASP.NetWindows Application  .NET Framework  C#  VB.Net  ADO.Net  
Sql Server  SharePoint  Silverlight  Others  All   

Hall of Fame    Twitter   Terms of Service    Privacy Policy    Contact Us    Archives   Tell A Friend