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Hello friends i need an explanation regarding .NET framework pre-requisite while installing the published application in the target machine.

As java is downward compatible, by which i mean that if i have installed java v1.6 and if the application is developed using java v1.5 (i also mean that only classes and packages available in 1.5 are used to build the appln.)

I am sure that the application developed will definitely run by installing the latest or higher versions of jre or j2se.

Similarly in the case of .NET platform suppose if i develop my application using .NET framework 3.5 and in the target machine i have installed .NET framework 4.0 (the latest) even then it prompts to install the .NET framework 3.5 why is this so?

The real time example is i have downloaded and tried installing MySQL workbench and also installed .NET framework 4.0 But it still asks to install the .NET framework 3.5 before running the MySQL installation.

My question is does .NET framework is downward compatible as java or .NET?

Vadim Kotov
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kunaguvarun
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2 Answers2

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Version Compatibility in the .NET Framework:

The .NET Framework 4 is backward-compatible with applications that were built with the .NET Framework versions 1.1, 2.0, 3.0, and 3.5. In other words, applications and components built with previous versions of the .NET Framework will work on the .NET Framework 4.

However, in practice, this compatibility can be broken by seemingly inconsequential changes in the .NET Framework and changes in programming techniques. For example, performance improvements in the .NET Framework 4 can expose a race condition that did not occur on earlier versions. Similarly, using a hard-coded path to .NET Framework assemblies, performing an equality comparison with a particular version of the .NET Framework, and getting the value of a private field by using reflection are not backward-compatible practices. In addition, each version of the .NET Framework includes bug fixes and security-related changes that can affect the compatibility of some applications and components.

If your application or component does not work as expected on the .NET Framework 4, use the following checklists.

For .NET Framework 2.0, 3.0, and 3.5 applications:

Check .NET Framework 4 Migration Issues for any changes that might affect your application and apply the workaround described.

If you are recompiling existing source code to run on the .NET Framework 4, or if you are developing a new version of an application or component that targets .NET Framework 4 from an existing source code base, check What's Obsolete in the .NET Framework for obsolete types and members, and apply the workaround described. (Previously compiled code will continue to run against types and members that have been marked as obsolete.)

If you determine that a change in the .NET Framework 4 has broken your application, check the Runtime Settings Schema to determine whether you can use a runtime setting in your application configuration file to restore the previous behavior.

If you encounter an issue that is not documented, file a Microsoft Connect bug and contact netfxcf@microsoft.com with the bug number.

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Mitch Wheat
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Yes, .Net 4 framework is backwards compatible with applications built on previous versions of .Net. You can see this link on MSDN for more info.

If you have .Net 3.5 or .Net 4 installed and a third party still requires either (or and older version) then the installer is not checking the correct prerequisite install conditions.

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