C#: throw invalid expression compilation

Question

I\'m using this code in order to check queryable value:

visitor.Queryable = queryable ?? throw new Exception(\"error message\");

Answer 1

This feature is only available post C# 7.0. See under Throw exception of What's New in C# 7.0.

If you are using an older VS and want to enable C# 7 features: Have a look at How to use c#7 with Visual Studio 2015? if not in VS 2017.

---

If you are working with a previous version of the C# compiler, as you must be due to the error then you cannot use the ?? operator this way as the throw does not return a right operand value. As the C# Docs say:

It returns the left-hand operand if the operand is not null; otherwise it returns the right operand.

The pattern is like this:

var result = someObject ?? valueToAssignIfWasNull;

To solve it write instead:

if(queryable == null)
{
    throw new Exception("error message");
}
visitor.Queryable = queryable;