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Posted 29 Nov 2005

Call a .NET component from an ASP Page

, 7 Dec 2005
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How to call a .NET component from VB6.0/ASP developed in either Microsoft Visual Basic® .NET or Microsoft Visual C#® .NET


The following steps outline how to call a .NET component from VB6.0/ASP developed in either Microsoft Visual Basic® .NET or Microsoft Visual C#® .NET.


  1. Launch your Visual Studio .NET

  2. Open your .NET Class Project

  3. Add a reference to the System.EnterpriseServices namespace

  4. At the top of the code file, add the following statements to specify the namespaces needed:

    using System.EnterpriseServices;
    using System.Runtime.InteropServices;

    Imports System.EnterpriseServices
    Imports System.Runtime.InteropServices
  5. Add the following statements before the namespace declaration to set the assembly options:

    [assembly: ApplicationName("ClassLibrary1")]
    [assembly: ApplicationActivation(ActivationOption.Server)]
    [assembly: ApplicationAccessControl(false,

    <Assembly: ApplicationName("ClassLibrary1")>
    <Assembly: ApplicationActivation(ActivationOption.Server)>

ClassLibrary1 – Sample Project

These attributes help specify how the .NET assembly will operate with COM+ services. The ApplicationName attribute allows one to specify the name of the COM+ services application that will host the .NET assembly when it is imported into COM+. You can specify any name you would like here. The ApplicationActivation attribute specifies the type of COM+ application being created. This attribute uses an enumeration called ActivationOption which specifies that the application is a server application. This means that when the component is activated, it will be hosted in a process separate from the process that called it. The ApplicationAccessControl attribute specifies whether the component will perform any access level checks.


Generate a strong name for the assembly using the .NET Framework Strong Name Utility (sn.exe). This utility generates a public/private key file that will be incorporated into the assembly. To create this key file, go to a command prompt and change directories to the location where the solution is stored.

Type in the command:

>cd C:\Program Files\Microsoft Visual Studio .NET 2003\SDK\v1.1\Bin
>sn –k "D:\DotNet Testing\ClassLibrary1\ClassLibrary1\obj\Debug\mykey.snk"

This will create the key file.

Add the strong file name to the assembly by adding an attribute in the AssemblyInfo code file that is part of the project. Locate the AssemblyInfo file in Solution Explorer and click it. In the code file, add the following attribute:

[assembly: AssemblyKeyFile(@"mykey.snk)] 

<Assembly: AssemblyKeyFile("mykey.snk")>

This attribute looks for the strong name key file that was previously created in the folder that was created for the solution. If there is an AssemblyKeyFile attribute in the AssemblyInfo file, replace it with this one.

  1. Build the solution. This will create the DLL file.

  2. Create type library file using your DLL file - Register for COM Interop.

    1. Place the DLL file to your virtual directory /bin folder.

    2. Type in the command:

      >cd "C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322"
      >regasm "D:\DotNet Testing\asp\bin\ClassLibrary1.dll" /tlb /codebase

      This will create the TLB file in your bin folder.

    3. Finally, you can call .NET components from VB6 or ASP:

      Dim Obj
      Set Obj = Server.CreateObject("ClassLibrary1.Class1") 


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Manoj Kumar G (IND)
Web Developer
India India
It is an inherent passion for Analytical applications that inspired me to study Physics at the graduate level. During these 3 years I was trained in systematic analysis of physical data and application of Mathematics and in due course of time this passion got transformed into an abiding interest towards automation. This motivated me to go for a higher level application oriented program in Software Development. During the last 6+ years I have enriched myself considerably well by working on various projects which really fine tuned my technical skills. I look forward to put into productive use the knowledge gained / insights developed and at the same time continue to learn enhancing my caliber and pursue a career of excellence, rooted in professional ethics, in the field of Software Development.

I have strong background in C#, ASP.NET, ASP, VB6.0 and SQL server 2000.

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Comments and Discussions

QuestionGetting 800a01ad error after Dll registration step Pin
Member 1106805127-Nov-17 0:05
memberMember 1106805127-Nov-17 0:05 
Questionregarding .net componet call from asp Pin
Member 262867710-Sep-15 0:08
memberMember 262867710-Sep-15 0:08 
AnswerRegister the .Net Component from the Component Service Pin
narayananbabun29-Oct-13 3:56
membernarayananbabun29-Oct-13 3:56 
GeneralGood Article Pin
srinivas GN27-Oct-10 1:00
membersrinivas GN27-Oct-10 1:00 
QuestionOs Hardening Automation Pin
Suthari12-Feb-10 8:42
memberSuthari12-Feb-10 8:42 
GeneralObject Reference not set to an instance of an object Pin
narayananbabun23-Nov-08 21:28
membernarayananbabun23-Nov-08 21:28 
I created object as how it was described but now i am getting an error in the line where i use the object to call a function. Please tell me what i am missing
GeneralYOU ROCK!!! Pin
wdwcrazyva27-Jun-08 13:50
memberwdwcrazyva27-Jun-08 13:50 
QuestionIntellisense Pin
Brian Silvers10-Sep-07 6:17
memberBrian Silvers10-Sep-07 6:17 
GeneralError while attempting to create an instance Pin
Amidu)24-Dec-06 8:33
memberAmidu)24-Dec-06 8:33 
GeneralThis is just a copy of an msdn library page... Pin
jo0ls3-Oct-06 17:02
memberjo0ls3-Oct-06 17:02 
QuestionCall a .NET component from an VB6.0 [modified] Pin
brahmareddy8131-May-06 1:47
memberbrahmareddy8131-May-06 1:47 
AnswerRe: Call a .NET component from an VB6.0 Pin
Alexander Turlov16-Jan-07 7:32
memberAlexander Turlov16-Jan-07 7:32 
GeneralI am getting Error Pin
shyamaji_200013-Mar-06 2:09
membershyamaji_200013-Mar-06 2:09 
GeneralCOM object not valid or not registered Pin
lieperik20-Feb-06 6:26
memberlieperik20-Feb-06 6:26 
AnswerRe: COM object not valid or not registered Pin
Alexander Turlov16-Jan-07 7:30
memberAlexander Turlov16-Jan-07 7:30 
GeneralRe: COM object not valid or not registered Pin
ZarrinPour5-Jun-07 5:09
memberZarrinPour5-Jun-07 5:09 
QuestionHelp! Pin
jsanjosem6-Dec-05 22:12
memberjsanjosem6-Dec-05 22:12 
AnswerRe: Help! Pin
jsanjosem7-Dec-05 13:00
memberjsanjosem7-Dec-05 13:00 

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Article Copyright 2005 by Manoj Kumar G (IND)
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