How Do Assembly Binding Redirects Resolve Version Conflicts in .NET Applications?

Assembly Binding Redirects: An In-Depth Explanation

Introduction

Assembly binding redirects play a crucial role in resolving version conflicts between assemblies. This article delves into the mechanisms behind binding redirects, addressing common queries and providing a comprehensive understanding of their functionality.

Binding Redirect Mechanism

A binding redirect in the Assembly Binding section of the app.config file specifies a mapping between an old version and a new version of an assembly. When the runtime encounters the old version, it automatically redirects the loading to the new version.

Major Version Specificity

Binding redirects typically specify only the major version number in the oldVersion and newVersion attributes. This is because the remaining version numbers (minor, build, revision) are assumed to be compatible. If not explicitly specified, the runtime will attempt to load the new version with the same minor, build, and revision numbers as the old version.

Version Changes

Version changes are not restricted to major versions. Binding redirects can be used to redirect any version range to a specific new version. However, if the major version is changed, all subsequent versions are also redirected, while changes to minor, build, or revision numbers within the same major version do not trigger a redirect.

Example

Consider the following binding redirect:

In this example, assemblies with a name of "FooBar" and a public key token of "32ab4ba45e0a69a1" will be redirected from version 7.0.0.0 to version 8.0.0.0 at runtime. All minor, build, and revision numbers within version 7.0.0.0 will be automatically redirected to their corresponding counterparts in version 8.0.0.0.

Additional Notes

• Binding redirects can be applied to any assemblies, not just those loaded explicitly by the application.
• Multiple binding redirects can be specified for the same assembly, but the runtime will only apply the most specific redirect (e.g., for a specific version range).
• Redirections are not transitive. If an assembly is redirected and it references another assembly that is also redirected, the second redirect will not be applied.

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