返回布尔值和字符串值的最佳做法是什么

Question

I've created a method that performs some validations against an XML Hierarchy that is dynamically generated by another Class in Javascript text during run time.

My method currently returns either True or False, which is helpful for anyone using my Class but I'd like to also return more informative information since there may be several reasons that can throw a False message.

At first I thought to change the return type from bool to some Generic Collection type having a String key and Boolean value I don't know if this is the best approach.

What is the Best Practice in this case?

Answer 1

Make a class like

public class ValidationResponse
{
    public bool Successful { get; set; }
    public string Information { get; set; }
}

and return object of ValidationResponse

Answer 2

One pattern, which is used in the TryParse methods of .NET datatypes (eg Int32.TryParse ), and is very common in the C world, is to return a boolean to signify success or failure. The user also has to pass in a value by reference to the method to receive the parsed value back.

For your circumstance, your method signature might look like:

bool DoSomething (out string anInformativeMessage)

HOWEVER I personally think the best approach is to return a Result class Dhinesh has described in his answer, as it's more flexible, and OO in nature. I'm adding this approach for completeness ;)

Answer 3

1. Create your own results class, which your method returns and which contains all the information you need. With this, you can more easily extend it in the future (as in dhinesh's answer.)

2. Another option is to use a Tuple object to store both the string and bool : Tuple<string, bool> would be your return type. (Only available in .NET 4.0 onwards)

Answer 4

The Rust std::result type should also work similarly for C#:

enum Result<T, E> {
   Ok(T),
   Err(E),
}

You either:

1. return an Ok type with the value
2. or an Err type with the error message

---

Old answer:

I don't know about best practice but if you only have the two following cases:

1. Return true, with no extra information
2. Return false, with extra information

Then you can simplify it down to just returning a string. If there is no error then you return an empty string which is the equivalent of an error code of zero.

string errorMsg = myObject.MyMethod();
if (errorMsg != String.Empty) {
    Console.Error.WriteLine(errorMsg);
}

Answer 5

Creating a Result class as a new return type as suggested in other answers has the problem of breaking existing code.

If you want/need to avoid that, you could introduce a new string LastError property containing error messages of the last call to your method, and keep the method signature intact. You'd use it like

bool success = myObject.MyMethod();
if(!success)
    Console.Error.WriteLine(myObject.LastError);

This approach is not well suited for multi-threading environments.

Answer 6

If it is expected that the XML Hierarchy will validate - Then I would say this is a typical example of where you should use an exception. The method then just returns void and throws on failure, like so:

void validateXMLHierarchy();

and to use

try
{
  validateXMLHierarchy();
}
catch (XmlValidationException ex)
{
  Console.Error.WriteLine(ex.Message);
}