在c＃中，是否可以将两个不同的类作为返回类型从一层传递到另一层？

Question

My application has n-tier architecture. I have different layers(Business Logic & Data Link & GUI). I am using some common classes to pass data from one layer to the other. I have a class(say RetrnValueCls ) which has just two variables Return value and Return Message . While I am passing data from one layer to the other, I need to return this Return Value Class along with the other class(say MasterItemsCls ) which has other variables.

Below are the methods

public MasterItemsCls GetMasterItemsMDL()
{
    /* Does some computations and assign them to
    attributes of MasterItemsCls and pass it other methods in other layers. */
}

public ReturnValueCls GetMasterItemsMDL()
{
    /* Does some computations and assign them to
    attributes of ReturnValueCls and pass it other methods in other layers. */
}

I want to return both the above classes( MasterItemsCls & ReturnValueCls ) as return type for the method GetMasterItemsMDL at once and also I don't want to combine both the classes. Please let me know if there is any way I can do that.

Answer 1

A function can only return a single value, so in that sense the answer is no.

Functions can have out parameters, so you could return one of the two values via an out parameter.

The cleanest way to handle this in my opinion is to use a third class to contain the other two. Tuple<T1,T2> can be used for that purpose:

public Tuple<MasterItemsCls, ReturnValueCls> MyFunction()
{
    // Do stuff
    return new 
    Tuple<MasterItemsCls, ReturnValueCls>(myMasterItemsCls, myReturnValueCls);
}

One disadvantage of Tuple<T1,T2> is that the values are accessed as the rather unintuitive Item1 and Item2 .

If you don't want to use Tuple<T1,T2> , it is easy to create your own class to contain MasterItemsCls and ReturnValueCls . That is my preferred approach.

Answer 2

You don't need to combine both classes but a possible and direct approach is to generate a class that contains one instance of each class you're trying to return.

public class YouClassName
{
     public MasterItemsCls MasterItemsCls {get; set;}
     public ReturnValueCls ReturnValueCls {get; set;}
}

Answer 3

A method can only return one object. You could possibly create some other class that has instances of each of these others.

Answer 4

Generics may be helpful as a wrapper for your return element.

You could do the following:

public ReturnValueCls<MasterItemsCls> GetMasterItemsMDL()
{

}

Your ReturnValueCls<T> expects a type parameter for its return type. So your retun type can would act as a wrapper for your desired return and be able to hold your return message.

---

Example of your class definition. May require some constraints:

public class ReturnValueCls<T>
{
    public T Value { et; set;}
    public string Message {get; set;}
}