C# - launch Microsoft foundation solver THROUGH Reflection

below you can find a trivial optimisation code I have written to check how Foundation Solver works. I am then trying to re-write this code using reflection, starting from the end of the code (step 6 in the code below).

I get a NullReferenceException when it comes to getting the type of the "Solution class": it seems that the fully-qualified name ("Microsoft.SolverFoundation.Services.Solution") of the "Solution" Class is wrong.

Can someone help me with that?

Thanks

class Program
{
    static void Main(string[] args)
    {
        // Get two input values
        Console.WriteLine("Input values of X and Y");
        Console.WriteLine("X value: ");
        double Xinput = Convert.ToDouble(Console.ReadLine());
        Console.WriteLine("Y value: ");
        double Yinput = Convert.ToDouble(Console.ReadLine());
        Console.WriteLine("");

        /* Create the optimisation problem */
        // 1) Creat the solver and model objects
        var solver = SolverContext.GetContext();
        var model = solver.CreateModel();

        // 2) Create variables
        var X = new Decision(Domain.RealNonnegative, "X");
        var Y = new Decision(Domain.RealNonnegative, "Y");

        // 3) Add them to the model
        model.AddDecision(X);
        model.AddDecision(Y);

        // 4) Add goals
        model.AddGoal("Goal", GoalKind.Minimize, X + Y);

        // 5) Add constraints
        model.AddConstraint("X_constraint", 0 <= X <= 500);
        model.AddConstraint("Y_constraint", 120 <= Y <= 3120);

        // 6) Solve optimisation
        // Solution solution = solver.Solve(); // This is what should be without reflection

        // rewritten with reflection
        Assembly executingAssembly = Assembly.GetExecutingAssembly();
        Type solutionType = executingAssembly.GetType("Microsoft.SolverFoundation.Services.Solution"); // <-- something wrong here??
        object solution = Activator.CreateInstance(solutionType); // HERE I GET THE ARGUMENT NULL EXCEPTION!
        MethodInfo solveMethod = solutionType.GetMethod("Solve");
        solveMethod.Invoke(solution,null);

        // 7) Print the outputs
        Console.WriteLine("Results:");
        Console.WriteLine("X: " + Math.Round(X.GetDouble(), 2));
        Console.WriteLine("Y: " + Math.Round(Y.GetDouble(), 2));
        Console.WriteLine("");

    }
}