Where did CUDA get installed in the computer

As Jared mentions in a comment, from the command line:

nvcc --version

(or /usr/local/cuda/bin/nvcc --version) gives the CUDA compiler version (which matches the toolkit version).

From application code, you can query the runtime API version with

cudaRuntimeGetVersion()

or the driver API version with

cudaDriverGetVersion()

As Daniel points out, deviceQuery is an SDK sample app that queries the above, along with device capabilities.

As others note, you can also check the contents of the version.txt using (e.g., on Mac or Linux)

cat /usr/local/cuda/version.txt

However, if there is another version of the CUDA toolkit installed other than the one symlinked from /usr/local/cuda, this may report an inaccurate version if another version is earlier in your PATH than the above, so use with caution.

Since EF needs to translate your LINQ statements to SQL statements, you can't do this. If you have complex comparison logic in your overridden Equals() method you will have to duplicate that in the LINQ statement.

Since LINQ uses deferred execution you could probably encapsulate that logic in a method that returns an IQueryable<T> you can incorporate elsewhere.

Here's an example:

public IQueryable<Foo> FoosEqualTo(IQueryable<Foo> allFoos, Foo target) {
    return from foo in allFoos
           where foo.Id == target.Id // or other comparison logic...
           select foo;
}

public Foo getFoo(Foo target) {
    return FoosEqualTo(DC.foos, target).FirstOrDefault();
}