Originally posted by: a.teuffel

Hi everybody,

I am creating a Visual Basic application to import and solve a previously created .lp model.

This works fine so far.

Dim cplex As New Cplex()
dim dual1 as double

cplex.ImportModel("model.lp")
If cplex.Solve() Then
   'do some stuff with the solution
   dual1 = cplex.GetDual(???)
End If

Now I want to get dual values of specific constraints.

I've heard of the .GetDual() method but I have not figured out how to use it. GetDual needs an IRange object as input defining the contraint(s). Since I only import the model I have not so much experience with creating models and using cplex language in visual studio.

The constraints have names c1, c2, ... from the lp-file.

What do I have to do now?

If you import  a model from a file then all the variables and constraints are stored in an instance of ILPMatrix. You can get a reference to this instance via cplex.GetLPMatrixEnumerator(). See for example the AdMIPex1.vb example that is shipped with CPLEX.  This example queries all the variables created from an imported file.