I'm trying to implement a method:
public Referee GetRefereeById(int refereeId)
{
var result = from b in Referees
where b.PersonId.Equals(refereeId)
select b;
return (Referee)result;
}
This method is supposed to return a referee object. Any idea what I'm doing wrong?
Try
return result.FirstOrDefault();
SingleOrDefault. This will throw an exception if multiple elements are returned by your query, and will return null if no elements are returned.Your select can return more than 1 referee. Try
public Referee GetRefereeById(int refereeId)
{
var result = (from b in Referees
where b.PersonId.Equals(refereeId)
select b).FirstOrDefault();
return (Referee)result;
}
You could use .Single(), but FirstOrDefault is a safer option. I am assuming PersonId should be unique, so that shouldn't matter, but if no matching data is found, Single will throw an exception.
You need to return a single referee, not many of them.
Use FirstOrDefault - Returns the first element of a sequence, or a default value if the sequence contains no elements. (MSDN: http://msdn.microsoft.com/en-us/library/bb340482%28v=vs.110%29.aspx)
public Referee GetRefereeById(int refereeId)
{
return Referees.FirstOrDefault(r => r.PersonId.Equals(refereeId));
}
This will return null if one isn't found.
In case you expect to find a result you should do
Return result.Single();
If not sure it exists do and check for null:
Return result.SingleOrDefault();
I would implement the Single() methods instead of the First(). Your method return a single referee to the caller. You want to make sure you actually get one unique referee in every case. When there is more then 1 matching your criteria you are introducing some very subtile bugs in your application. Assuming you are working against the correct record but instead you could be retrieving a complete different one.
Better use the First() methods if you have a list that you order on some sort of record and really intend to get the first row based on the ordering.
try this:
public Referee GetRefereeById(int refereeId)
{
var result = from b in Referees
where b.PersonId == refereeId
select b;
return result.FirstOrDefault();
}
there is also no need to do the cast for returning the result.
when you say it is supposed to return the object, what does it do?
var result = (from b in Referees
where b.PersonId.Equals(refereeId)
select b).SingleOrDefault();
return result;
This returns a Referee object.
Your query (more specifically the Where function) can return zero results. Use Single, SingleOrDefault, First or FirstOrDefault depending on your needs.
e.g. return (Referee)result.SingleOrDefault();
