Which is better between a readonly modifier and a private setter?

Question

I\'ve been working on creating a class and suddenly a thought came to my mind of what is the difference between the two codes:

public readonly string Product         


        

Answer 1

Generally, it is not encouraged in .NET to expose member fields publicly, those should be wrapped by a property. So let's assume you might have

private readonly string productLocation; 
public string ProductLocation { get { return productLocation; } } 

vs

public string ProductLocation { get; private set; }

In this setup, and ignoring what one might be able to accomplish via reflection, the semantics are that in the first case, the productLocation variable can only be initialized in place and in the class constructor. Other members of the class cannot alter the value. External consumers have no ability to set the value.

In the second version, external consumers continue to have no access towards setting the value. However, the class itself can change the value at any time. If all you have is a DTO (that is, a class that only transports data, it has no logic expressed via methods), then this is essentially not all that different from the readonly version. However, for classes with methods, those methods could alter the value behind ProductLocation.

If you want to enforce the concept of an immutable field post-construction, use readonly. But for a DTO, I might go for the private set; option, mainly because it is less boilerplate code.