How do I cast Class FooObject to class BarObject which both implement interface IObject? [duplicate]

问题

This question already has answers here:

Casting between two types derived from the (same) interface (9 answers)

Casting between classes that share the same interface (7 answers)

Casting a interface derived class to another derived class (1 answer)

Closed 10 months ago.

I have 2 classes which implement the same interface. But somehow I cannot cast them from one to another.

Here's an example:

public interface IObject {
    // ...
}

public class FooObject : IObject {
    // ...
}

public class BarObject : IObject {
    // ...
}

-

If I do it like this, VS will mark it as Cannot convert type 'FooObject' to 'BarObject'

var foo = new FooObject();
var bar = (BarObject)foo; // Build error

-

If I do it like this, there is no build error, but when called, it throw System.InvalidCastException: Unable to cast object of type 'FooObject' to 'BarObject'.

var foo = new FooObject();
var bar = (BarObject)(IObject)foo; // No build error, but InvalidCastException gets thrown

-

So, how do I cast/parse/convert an implementation (FooObject) of an interface (IObject) to another implementation (BarObject) of that same interface?

Solution:

I fixed this by creating an explicit conversion operator:

public class FooObject {
    // ...
    public static explicit operator BarObject(FooObject fooObject)
    {
        // ...
    }
}

Thanks to CodeCaster.

来源：https://stackoverflow.com/questions/55047418/how-do-i-cast-class-fooobject-to-class-barobject-which-both-implement-interface