Can my .Net app reference two different versions of a .net framework library?

Question

Say I have two projects, P4 and P3, targetting .net 4.0 and 3.5 respectively.

Each project also has a reference to System.Data. In the case of P4, it will be to System.Data v4.0.0.0 In the case of P3, it will be to System.Data v2.0.0.0

Project P4 also references P3.

If P4 is loaded and executed, it uses the .net 4.0 CLR. At runtime, references to System.Data seem to resolve to v4.0 inside both P4 and P3. I can override this by using assemblyBinding redirects, but then both P4 and P3 resolve to v2.0.

Is there any way I can configure my application so that P4 uses v4.0 and P3 uses v2.0?

Answer 1

If you have control over P3, yes. Go to the references section of the project, find the System.Data reference, and view it's properties window (right-click -> Properties).

Select "True" for the "Specific Version" property. Recompile, redeploy, etc.

Note that this will cause all sorts of runtime failures if .NET 2, 3, or 3.5 are not installed on the machine when the assembly attempts to load.

Edit

I've tried this, but with no luck. P3 still runs v4.0. Do you know if this setting would have any visible effect in the assembly generated for P3? E.g. The manifest says ".ver 2:0:0:0" whether "Specific Version" is set to true or not.

Try adding this to your app.config:

<configuration>
  <startup>
    <supportedRuntime version="v2.0.50727" />
    <supportedRuntime version="v4.0" />
  </startup>
</configuration>

Answer 2

Have a look at this : In-Process Side-by-Side It might be of some help.