Question

Here’s my query:

from f in DataAccess.Data.FList
join fA in DataAccess.Data.FAppsList on f.ID equals fA.fID into fApps
from fA in fApps.Where(fA => fA.Year == reportYear).DefaultIfEmpty() 
join fSrc in DataAccess.Data.FSourcesList on new { ID = fA.sourceID, CropYear = reportYear } 
equals new { ID = fSrc.ID, CropYear = fSrc.CropYear }

I get Object reference null exception if fA == null. I am doing a left join on fA so it could be either null or not null value. How do I rewrite this section of query so that the query does not throw exception if fA is null.

Thanks much!

Answer 1

The common construct in the ternary conditional operator (?:) which can be used to safeguard invoking a member on a null-valued expression is:

foo != null ? foo.bar : anExpressionThatDoesNotUseFoo

In context:

new {
  ID = fA != null ? fA.sourceID : 0, // or as appropriate
  ..
}