The Sage CRM .NET API has been part of the product's development and customisation architecture for many years. It allows developers to create compiled application extensions that work within the context of Sage CRM, use CRM metadata, respect the CRM security model, and generate interfaces that look and behave like standard Sage CRM pages.
It is important to recognise that the .NET API is not simply an optional SDK used by partners for custom development. It is also used by Sage itself to deliver functionality within the product.
For example, the standard Relationships feature is implemented using the .NET API. The API communicates with the main Sage CRM eWare.dll through a COM interoperability layer and allows the resulting pages to make use of Sage CRM metadata and context.
The Company Narrative, introduced in Sage CRM 2023 R1, was also developed using the .NET API. This feature analyses the information associated with a company and generates a near-natural-language summary of the relationship with that customer.
The .NET API is also an important dependency within the Sage 300 and Sage CRM integration. The Sage 300 integration installs components within Sage CRM, including Custom .NET components used as part of the integrated experience.
Why are we looking at the .NET API now?
The Sage CRM .NET API currently depends upon Microsoft .NET Framework 2.0 technology.
.NET Framework 2.0 and 3.0 components remain supported when installed as part of .NET Framework 3.5 SP1. Microsoft has confirmed that support for .NET Framework 3.5 SP1 ends on 9 January 2029.
This does not mean that Sage CRM .NET components will suddenly stop working on 10 January 2029. It does mean, however, that continuing to depend upon an unsupported Microsoft runtime would create increasing security, compatibility and supportability concerns.
We therefore need to address this dependency well before that date.
What is Sage investigating?
There are several possible approaches, and we do not want to prescribe the solution before the engineering investigation has been completed.
One important area being investigated is whether the existing Sage CRM .NET API can be moved to a later, supported version of the .NET Framework while retaining the existing architecture and COM interoperability with eWare.dll.
This could potentially provide the least disruptive route for customers and partners. The investigation needs to establish whether existing Sage CRM .NET components can continue to run unchanged, whether they would simply need to be recompiled against updated Sage CRM libraries, and whether any source-code changes would be required.
We also need to test Sage's own use of the API, including the Relationships feature, Company Narrative and the Sage 300 integration.
Binary compatibility is particularly important. Many customers and partners have invested in .NET application extensions over a long period, and a good customer experience means avoiding unnecessary redevelopment wherever possible.
At the same time, we are looking beyond simply updating the underlying .NET Framework.
Sage CRM already provides extensive REST API capabilities, including CRUD operations and discovery of CRM metadata. Our investment in the Enriched Semantic Schema (coming in Sage CRM 2026 R2) extends this API-first approach by providing richer information about CRM entities, fields, relationships and their business meaning.
We are also considering how low-code and no-code mechanisms could increasingly be used to create Sage CRM interfaces directly from metadata. These approaches may, over time, reduce the number of scenarios in which developers need to create compiled .NET components at all.
The aim is therefore not simply to replace one technology dependency with another. We want to protect existing investments while continuing to develop a more open, metadata-driven and maintainable extension model.
What is the timescale?
This work is currently scheduled for Sage CRM 2027 R1, which is planned for release at the end of March 2027.
Depending on the outcome and scope of the engineering work, delivery may move to Sage CRM 2027 R2, planned for the end of September 2027.
The latest viable release would be Sage CRM 2028 R2, planned for the end of September 2028. This would still provide a transition point before Microsoft's support for .NET Framework 3.5 SP1 ends on 9 January 2029, although our intention is to provide customers and partners with considerably more time than this wherever possible.
What does this mean for developers today?
There is no immediate need to stop using existing supported Sage CRM .NET functionality or to redevelop working applications.
Partners developing new solutions should, however, continue to consider the most appropriate extension mechanism for each requirement. Where functionality can be implemented through the REST API, metadata and other supported interfaces, these provide useful ways of reducing dependencies on the older runtime architecture.
Where the .NET API remains the appropriate mechanism, developers should continue to use the supported SDK and development practices.
As our investigation progresses, we will provide further guidance to partners about compatibility, migration and the recommended approach for future development.
The important point is that Sage is aware of the January 2029 Microsoft lifecycle deadline and is actively planning for it. The .NET API remains important both to Sage CRM itself and to many customer and partner solutions, so providing a supported transition with the minimum possible disruption is central to this work.