Many Class Library and need only one to load in a project -C# -

i'm working on program having 3 class library file in project.

after loading class library, return project , use selected library rest of project.

it's configuration project. - c#

    using myref; //class1     using newref; //class2     using revisionref; //class3     public static string mchoose { get; set; }     public string myconfiguration(string pactivity)     {         string _retval = "";         if (pactivity== "class1")         {              class1 _class1 = new class1();             _retval = _class1;         }         else if (pactivity== "class2")         {              class2 _class2 = new class2();             _retval = _class2;         }         else if(pactivity== "class3")         {              class3 _class3 = new class3();             _retval = _class3;         }         return _retval;     } 

i suspect class names wrong eg class1 should of type myref can't assign object string eg _retval = _class1; if want return class whole method have rewritten return object of whatever class decide create. want this:

switch (pactivity) {     case "class1":         myref _class1 = new myref();                 break;     case "class2":         newref _class2 = new newref();         break;     case "class3":         revisionref _class3 = new revisionref();         break;     default:         break; } 

then whichever class created have methods of class type.