
Side-by-Side Execution in Earlier Versions
The relationship of the .NET Framework versions 2.0, 3.0, and 3.5 differs from the relationship of versions 1.0, 1.1, and 2.0. The .NET Framework versions 1.0, 1.1, and 2.0 are completely separate from each other, and one version can be present on a computer regardless of whether the other versions are present. When versions 1.0, 1.1, and 2.0 are on the same computer, each version has its own common language runtime, class libraries, compiler, and so forth. Application developers can choose which version to target. For more information, see Side-by-Side Execution, Targeting a Specific .NET Framework, and Targeting Specific .NET Frameworks with MSBuild.
The .NET Framework 3.5 and later versions do not support side-by-side execution.