Imagine you are developing a .NET application that runs perfectly at first. Suddenly, unexpected runtime errors occur – even though your main project does not explicitly include additional packages. How can this phenomenon be explained?
Often, the cause is a transitive dependency: a library such as Entity Framework Core is silently included in your project via another NuGet package. This issue can lead to version conflicts or even hard-to-diagnose runtime errors like the `MissingMethodException` in complex application scenarios. Without targeted management of these dependencies, the effort required for error resolution can become significant.
Understanding the Problem:
Transitive References vs. Transitive Dependencies
Transitive References
In a multi-layered solution structure, for example, Project A directly references Project B, which in turn uses Project C. In this way, Project A has an indirect (transitive) reference to Project C – even if it is not explicitly listed in the `.csproj` file.
Transitive Dependencies
With external NuGet packages, the problem arises when a dependency is introduced through a referenced package but does not appear in the main project’s `.csproj` file.
Example:
- If Project A references (e.g., `PackageX`) that internally depend on EF Core (specific version), EF Core is included transitively – even though Project A never explicitly added it.
Isn’t it remarkable how quickly such subtle dependency chains can emerge in large projects without being noticed?
A Typical Scenario in .NET
In many .NET applications, Entity Framework Core (EF Core) is used as the data access library. Even if the main project does not directly reference EF Core, it can be silently included as a transitive dependency via another utility or data access package.
At first, everything seems to work fine—EF Core provides a stable API. However, when upgrading the .NET framework or integrating new features, version conflicts may arise, leading to hard-to-diagnose runtime errors.
Solution Approaches
To prevent the unwanted propagation of packages, two main approaches are available:
- Restricting specific packages using `PrivateAssets=“all“`
- Disabling transitive project references with `<DisableTransitiveProjectReferences>true</DisableTransitiveProjectReferences>`.
Both approaches are examined below.
Approach 1: Using`PrivateAssets=“all“`
By adding the attribute `PrivateAssets=“all“` in the PackageReference, you prevent the respective library from being passed on to other projects in the dependency hierarchy. This ensures that the package – and its transitive dependencies – remain available only within the current project.
Advantages:
- Granularity: Decide on a package-by-package basis whether a dependency should be inherited.
- Avoidance of Side Effects: Prevents problematic libraries from being automatically transferred to subordinate projects.
Disadvantages:
- Increased Configuration Effort: If another project needs the same library, it must be explicitly referenced again.
Approach 2: Using <DisableTransitiveProjectReferences>
With <DisableTransitiveProjectReferences>true</DisableTransitiveProjectReferences> set in the .csproj file, all transitive project references are disabled. Every project must then explicitly list all the required packages.
Advantages:
- Increased Transparency: All dependencies are explicitly visible and controllable.
- Prevention of Unintended Inclusions: No “hidden” libraries are automatically added to the project.
Disadvantages:
- Higher Maintenance Effort: Explicitly listing all dependencies can create a significant administrative overhead, especially in larger projects.
- Risk of Omissions: Essential dependencies might be overlooked, leading to compile-time or runtime errors.
Comparison of Both Approaches
In summary, both approaches have their pros and cons. The decision largely depends on the requirements for granularity, maintenance effort, clarity, and flexibility in the specific project.
Practical Example: Abstraction and Interface Encapsulation
Consider a specific application: a .NET Standard library named Common encapsulates various helper methods and tools and internally includes a data access package that brings EF Core as a transitive dependency. In this case, it is advisable not to expose EF Core-specific classes in the public API; instead, these should be abstracted through interfaces.
Example Implementation:
Configuration in Common.csproj:
This approach ensures that EF Core remains exclusively available internally – the main application only interacts with the interface without needing to know the underlying implementation.
Advanced Strategies and Alternative Approaches
In addition to the configuration options discussed above, other strategies can help minimize version conflicts and the issues of transitive dependencies:
- Binding Redirects:
Especially in older .NET Framework applications, binding redirects can help resolve conflicts between different versions of the same library.
- Modular Architectures:
Separating the application into clearly defined modules allows for targeted isolation of dependencies. This makes it easier to control unwanted side effects
Tips and tricks
Should we not always question whether a focus solely on .csproj configurations in highly complex systems is truly the optimal solution?
Summary
Transitive dependencies represent a serious issue in complex .NET projects. Seemingly insignificant libraries like EF Core can – when included via other NuGet packages – lead to significant version conflicts and runtime errors. Consistent separation of dependencies and the targeted use of measures such as PrivateAssets=“all“ or <DisableTransitiveProjectReferences> offer practical solutions. It is essential to weigh whether the administrative effort is justified by the benefits and how long-term maintainability can be ensured.
Abstractions, explicit references, and tools like dotnet list package –include-transitive or NDepend help create a more stable codebase and reduce maintenance efforts.
Regularly reviewing dependency hierarchies using tools like dotnet list package – include-transitive or NDepend is indispensable.
Is it not ultimately the task of every developer to continually question whether the current architecture still meets the growing demands of modern applications?
I think so…!