Dapper handling returned empty result set

Question

We are using Dapper to map our sql data and so far it has worked very well. I have a case though where we are doing something similar to:

someObject = con.Query<T>("GetInfoSproc", p, commandType: CommandType.StoredProcedure).Single();

This works great as long as the stored procedure I'm calling returns data. There are times where the stored procedure might not return a result and return an error in a out parameter. This seems to cause a problem in Dapper because dapper throws the error:

"When using the multi-mapping APIs ensure you set the splitOn param if you have keys other than Id"

Is there a way to write the query so it can properly handle the case when an empty result is returned or is this a limitation of Dapper?

I've opened an issue on google code on this for further discussion: code.google.com/p/dapper-dot-net/issues/detail?id=57 — TodK
For those who may come across this question, I found this answer helpful. — Dan Hogan

Brett Veenstra Brett Veenstra · Accepted Answer · 2017-05-26T15:49:43

SingleOrDefault() is your friend here

Try this:

someObject = con.Query<T>("GetInfoSproc", p, commandType: CommandType.StoredProcedure).SingleOrDefault();
if (someObject != null)
{
  // operate on your results here
}
return someObject;

also you'll need to make sure T is Nullable

Dapper handling returned empty result set

1 Answers