Why is wrong this inline if?

Question

If have the following statement:

return this.revision.HasValue ? this.revision : throw new InvalidOperationException();

I thought it would compile as the throw is breaking the normal flow and it shouldn't be a problem to not return a value but it does not build.

Is there a way to put right this statement or why is this not allowed?

Thanks.

EDIT: this.revision is int? and the method returns int.

EDIT 2: if I have this method

public int Test()
{
    throw new Exception();
}

The compiler does not complain about not returning a value, I expected the same thing from an inline if ... at least we know that can be done as it's already done in methods.

Answer 1

Converting comment to an answer:

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.

?: Operator

As int? cannot be converted to an exception, and throw is not an expression, hence the error within your code.

Answer 2

I suppose the problem is in the fact that this.revision is a nullable type and InvalidOperationException() is a SystemException. You cannot have two different types in an if statement like:

return (a>b)? DateTime.Now : 2;

Please look here: http://msdn.microsoft.com/en-us/library/vstudio/ty67wk28.aspx

condition ? first_expression : second_expression;

The condition must evaluate to true or false. If condition is true, first_expression is evaluated and becomes the result. If condition is false, second_expression is evaluated and becomes the result. Only one of the two expressions is evaluated.

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 3

It's because in a ternary expression, the latter two expressions act as a substitute to each other and their return value needs to be of same type or implicitly convertible to type of the variable being assigned.
Clearly, an Exception has different type than an int.

MSDN:

If condition is false, second_expression is evaluated and becomes the result.