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Case Study: Migration from VB6 to .NET


The client is a US-based consulting company, holding a group of experienced developers who have worked for decades of years.

The client asked us to bring enhancements and modifications to the former VB 6 application using .NET for their Securities client.


  • The client possessed a legacy application developed with VB6. But it was hard for them to find resources within their organization specializing in VB6, thus it would not be cost-effective if the maintenance was carried out through the former architecture.
  • As the former specification was missing, it is not very easy to understand the requirements just by analyzing the code.
  • We were required to not only upgrade the code, but also transfer the database from Access being used to Microsoft SQL Server 2005. The legatary database was poorly designed without essential constraints, leading to many tables containing similar but inconsistent data in the database.


Technology required

  • .NET Framework 2.0
  • Smart Client Software Factory
  • NHibernate 1.2
  • DevExpress 7.2
  • Crystal Report
  • Because the client would like to rewrite the application with .NET solution, considering the scalability and a more reasonable architecture of the system, we adopted Smart Client Software Factory to create the framework of the whole system.

    Meanwhile, NHibernate was adopted as Data Access Layer, which not only speeded up the development progress, but also made the code clearer and more legible. In addition, DevExpress was utilized as the main controls of presentation tier which gave the application a modern, professional and easy-to-use look.

  • Sufficient and effective communication was essential for this project as the specification was missing. In order to ensure our work right, periodical products were submitted to the client for confirmation, such as Model Design, Prototype and etc. We also discussed the specific and complex issues with the clients via Skype meeting frequently.
  • We redesigned the database in SQL Server 2005 based on the business requirement. We merged all the similar but inconsistent data into one to ensure the data unique before importing data to our new database.

Benefits to the Client

  • The new version of application can now meet all the requirements of the client, including the new features.
  • The new system is established with excellent extensibility and maintainability. The client is now able to add new functions by himself with ease in future .
  • The new application is easier to use, and has fantastic face.
  • The client updated the system in scheduled time.