Question

I am trying to use Linq to get a Guid from an XAttribute value …

XDocument __xld = XDocument.Parse(
"<Form sGuid='f6b34eeb-935f-4832-9ddc-029fdcf2240e'
 sCurrentName='MyForm' />");

string sFormName = "MyForm";

Guid guidForm = new Guid(

    __xld.Descendants("Form")
    .FirstOrDefault(xle => xle.Attribute("sCurrentName").Value == sFormName)
    .Attribute("sGuid").Value

);

the thing is, i would like to return Guid.Empty if the XAttribute is missing, or if the XElement is not found, (or something goes wrong!) …

Can i one-liner this concept, or do i need to execute the query first to see if an XElement has been found with a matching sCurrentName and return Guid.Empty if the query returns nothing …

---

UPDATE

Thanks to Miroprocessor, i have ended up with the following …

Guid guidForm = new Guid(

    (from xle in __xld.Descendants("Form")
    where xle.Attribute("sCurrentName") != null && xle.Attribute("sCurrentName").Value == sFormName
    select xle.Attribute("sGuid").Value).DefaultIfEmpty(Guid.Empty.ToString()).FirstOrDefault()

 );

BUT(!) i think the Guid.Empty.ToString() could be avoided if i could create the Guid inside the query (if that is possible).

Answer 1

try

 var guidForm =(from xle in __xld.Descendants("Form")
                 where xle.Attribute("sCurrentName").Value == sFormName
                 select new {Value = xle.Attribute("sGuid").Value==null?Guid.Empty:new Guid(xle.Attribute("sGuid").Value)}).Single();

so to access the result you will write guidForm.Value

or try that

 Guid guidForm =new Guid(from xle in __xld.Descendants("Form")
                 where xle.Attribute("sCurrentName").Value == sFormName
                 select xle.Attribute("sGuid").Value==null?Guid.Empty:xle.Attribute("sGuid").Value).Single());

but I am not sure that will work correctly