OneStream, a corporate performance management (CPM) platform, is built on the Microsoft .NET framework, that supports both VB.NET and C# for business rule development. Both languages share the same runtime environment that is known as the .NET Framework. VB.NET has traditionally been favored, especially in finance-related functions. VB.NET does have similarities to Excel’s VBA—making it more accessible to finance professionals who are not full-time developers. However, in recent years, C# has gained significant traction, especially with more technically complex solutions and shared business rules.
In OneStream, shared business rules can be written in either VB.NET or C#, giving developers the freedom to choose based on preference or project requirements. However, item-specific business rules—those tied to a specific dimension, transformation, or form—must still be authored in VB.NET. That said, OneStream is steadily moving toward a C#-first model. Starting with version 7.1, support for C# business rules became more robust, and in the most recent platform updates—especially version 8.0 and beyond—C# has become the default in many marketplace solutions. Notably, several Financial Close extensions, such as Account Reconciliations and Transaction Matching, now require C# for any customization or rule development, reflecting this shift.
The platform’s migration from .NET Framework to .NET 6 in version 8.x is another development. This transition improves performance and scalability but also introduces some changes that can impact coding practices. Legacy VB.NET rules may experience compilation issues due to outdated syntax or incompatible references, prompting many teams to restructure their codebases in line with the updated .NET framework.
The developer community generally views VB.NET as a language with limiting features, while C# is considered the modern standard for .NET development. This sentiment is being adopted by OneStream. For current and future projects, developers and administrators are encouraged to adopt C# for better alignment with OneStream’s roadmap and Microsoft’s broader .NET ecosystem. Still, VB.NET remains relevant for certain rule types and legacy applications, so understanding both remains crucial.
In summary, while VB.NET maintains a presence within OneStream C# is increasingly the preferred and sometimes required language—especially in new marketplace solutions and in platform versions 8.0 and above. With the move to .NET 8, developers should prepare to refactor older rules and adopt C# where possible to ensure compatibility, performance, and long-term maintainability.
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