Get class by string value

Question

I have an abstract class with a few derived class

public abstract class MyObject {     public string name { get; set; }     public bool IsObject(string pattern);     ... }  public class MyObjectA : MyObject {     public string name { get { return "MyObjectA"; } set; }     public bool IsObject(string pattern) { ... }     ... }  public class MyObjectB: MyObject {   public string name { get { return "MyObjectB"; } set; }   public bool IsObject(string pattern) { ... }   ... } 

Now I want to have a function, which returns my the specific class (MyObjectA / MyObectB) based on a string. The problem is, that I have a lot of if/else-clauses to get that:

public MyObject Create(string pattern) {     MyObjectA obj = new MyObjectA();     if(obj.IsObject(pattern)     {         return obj;     }     else     {         MyObjectB objb = new MyObjectB();         if(objb.IsObject(pattern);             return objb;         else             ...     } } 

That looks just awful. What would be a better way to do this?

Answer 1

Yes, use Reflection.

You can use Type.GetType to get an instance of the Type for the class by string, then instantiate it using Activator.CreateInstance, something like this:

public MyObject Create(string pattern) {     Type t = Type.GetType(pattern);     if (t == null) {         throw new Exception("Type " + pattern + " not found.");     }     return Activator.CreateInstance(t); } 

You could use Activator.CreateInstance(string, string) overload also, but this would not directly return a new instance of the Type required.

Answer 2

You can use Reflection or System.Activator.CreateInstance to create an instance based on the Type or TypeName as string.