Question

Possible Duplicate:
C# Implicit/Explicit Type Conversion

I have an int that I am attempting to box, so as to use it in a constructor which takes as a parameter object of CustomType.

An example of what I mean.

 int x = 5;
 object a = x;

 CustomType test = new CustomType(a)

 //constructor in question
 public CustomType(CustomType a)
 {
   //set some variables etc
 }

Howver I get the following error

 The best overloaded method match for X has some invalid arguments.

So obviously I’m way off the mark. Where am I going wrong? Is boxing the right solution or should i be looking at type casting?

Answer 1

That constructor takes a CustomType type as a parameter; you’re passing it an int. An int is not a CustomType, and the C# language knows of no implicit conversions from int to CustomType. That’s why you’re getting an error.

Casting the int to an object doesn’t change the fact that it’s still not a CustomType.

Looking at that particular constructor, it’s a copy constructor. It takes a type of itself as a parameter. There is (one would hope) another constructor that takes another parameter, whether that’s an int, or some other type that you haven’t mentioned, or possibly no parameters and you need to just set a property after creating a default object.

As for actual solutions, there are many. Here are a few:

1. Add an additional constructor to CustomType that accepts an int.
2. Define a function that takes an int as a parameter and returns a CustomObject; this would be a “conversion” function that you could use.
3. Use a default constructor of CustomType and set a property with your integer (may or may not be applicable, depending on what CustomType does.

Boxing doesn’t seem to be related to the issue at hand. It’s not something that you should use to pass an integer to a custom type. If you would like to know more about what boxing is, how it works, or when it’s useful then consider asking a question that addresses those points because this particular problem would be harmed by using boxing as a solution, not helped.