C＃运营商？ 抛出异常

Question

I have following code:

public int Number(int x)
{
    return x > 0 ? x : throw new Exception();
}

The goal is very simple, with operator '?' I want to check some value, if it satisfies condition return that value, if not - throw some error. but VS Intellisense says: Invalid expression term throw; Am I forced to use other operators?

PS I guess that it's same as return throw new Exception(); But still want to be sure.

Answer 1

Write this instead:

public int Number(int x)
{
    if(x <= 0) throw new Exception();
    return x;
}

The conditional operator needs a common base-type to be returned, but there is none for int and Exception . In particular throwing something isn´t ment to be the same as returning something so even if your method would return an Exception (which was quite weird) this wouldn´t be possible.

From MSDN :

Either the type of first_expression and second_expression must be the same, or an implicit conversion must exist from one type to the other.

Answer 2

您可以在C＃7中执行此操作。您的方法可以进一步签约：

public int Number(int x) => x > 0 ? x : throw new Exception();

Answer 3

Prior to C# 7.0, if you wanted to throw an exception from an expression body you would have to:

return x > 0 ? x : new Func<int>(() => { throw new Exception(); })();

In C# 7.0 the above is now simplified to:

return x > 0 ? x : throw new Exception();

Answer 4

With ? expression both sides must return same type, which is not true in your case. Replace with if(x > 0) return x throw new Exception();