Question

I have a Linq query which I am selecting into a string, of course a string can contain null!

So is there a way I can throw an exception within my Linq query, if I detect a null?

Can I decorate my class with an attribute that won’t let it allow null?

I would like to wrap my Linq query in a try catch, and as soon as a null is detected then it would enter the catch, and I can handle it.

Edit

Here’s my Linq query, it’s quite simple currently. I am going to extend it, but this shows the basic shape:

var localText = from t in items select new Items { item = t.name }

Basically item is set to t.name, t.name is a string so it could be empty / null is this perfectly legal as its a string and strings can hold NULL.

So if it returns NULL then I need to throw an exception. Actually it would be handy to be able to throw an exception is NULL or empty.

I seemed to remember some kind of Attributes that can be set on top of properties that says "Don’t accept null" etc.?

Edit

I think I found it: http://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.requiredattribute.aspx

This doesn’t allow null or strings so I presume it throws an exception, I have used this with MVC but I am not sure if I can use it with a standard class.

Answer 1

As a string being null isn’t particularly exceptional, you could do something like:

var items = myStrings.Where(s => !string.IsNullOrEmpty(s)).Select(s => new Item(s));

UPDATE

If you are reading this data from an XML file, then you should look into LINQ to XML, and also use XSD to validate the XML file rather than throwing exceptions on elements or attributes that don’t contain strings.