如何强制编译器检查是否设置了特定属性

Question

In the below class I want to force the compiler to check the PropC whether its set, and if not, show the error in compile mode.

public class ClassA 
{
    public object PropA { get; set; }
    public object PropB { get; set; }
    public object PropC { get; set; }        
}

I know that I can use the PostShart to create custom attribute, but I want to use .NET built in class.

Answer 1

This is not a default feature of the .NET framework.

However, you can use the Code Contracts package to ensure Object Invariants .

You can configure the settings to run Static Code Analysis on your classes to ensure that verifiable invariants are met. As a fall back, you will get runtime safety of these contracts, because accession of the property with an invalid return value will result in a runtime error or debug assertion. This is accomplished by the Code Contract package performing rewriting of your code during compilation and inserting additional code to validate your contracts.

Note, that these behaviors are all dependent upon the settings that you configure. The package is too complex to explain in a stackoverflow answer, but you can get read the manual/documentation at http://research.microsoft.com/en-us/projects/contracts/userdoc.pdf .

Answer 2

I though it would be similar to check if your program will finish , but I think you want much more scoped version: "if my object created make sure the property is set before object leaves the function it was created in". It is possible in theory but C# compiler does not provide a way to do it. I believe broader check "if property assigned before usage" would not be possible at compile time at all.

Refactoring maybe better approach - if you simply not allow creating invalid objects it is much easier to prove that such objects are not present in the program. Ie factory method pattern maybe one option:

public class ClassA 
{
   public object PropC { get; private set; }        
   private ClassA (){};
   public Create (object propC)
   {
      return new ClassA{ PropC = propC };
   }
 }

Answer 3

What you are asking for is only available at run-time, not compile time. You should use unit tests to check if the property is being set.