Static type determination in c#-CodePudding

I'm sure I just don't know what to call this, but I'm trying to have a switch in my code to make my objects one of two subtypes, call them X_A and X_B, both subtypes of X. The code switch is a constant / static variable (basically I want to be able to choose between two types of internal database quickly at compile time).

I see 2 options:

Use if statements:

    X theObj;
    if (theType=="A") theObj = new X_A();
    else theObj = new X_B();

use reflection (as here)

    Type type = typeof(X_A);
    X theObj = (X)Activator.CreateInstance(type);

Is there a cleaner way? One like (2) but with static type checking? Maybe compiler directive or something?

(Also, the reason I just don't change the one line of code creating the object is that there are actually several of these made throughout my code, so I don't to change each one.. hence preference for a better version of (2).)

CodePudding user response：

If it is at compile time then use a #if compile-time directive.

#define USE_A

class Foo
{

    X NewX()
    {
#if USE_A
       return new X_A();
#elif USE_B
       return new X_B();
#else
       throw new NotSupportedException();
#endif
    }

}

You can define USE_A or USE_B on top of the code in order for the compiler to pick up the correct branch.