Multi Mapping in Dapper

Question

Using dapper. when I evaluate this:

var trains = conn.Query<Train, TrainDriver, Train>( "Select T.TrainId,T.OperatorId,T.TrainDescriptor,T.DriverId,TD.TrainDriverId,TD.Name,TD.Salary from trains as T" + "Inner Join TrainDrivers as TD on (T.DriverId = TD.TrainDriverId)" + "Where T.TrainId = @id", (t, td) => { t.Driver = td; return t; }, new {id = id}, null, true, "TrainDriverId");

It seems I am getting a SQLException : {"The multi-part identifier \"T.DriverId\" could not be bound.\r\nThe multi-part identifier \"T.TrainId\" could not be bound.\r\nThe multi-part identifier \"T.TrainId\" could not be bound.\r\nThe multi-part identifier \"T.OperatorId\" could not be bound.\r\nThe multi-part identifier \"T.TrainDescriptor\" could not be bound.\r\nThe multi-part identifier \"T.DriverId\" could not be bound."}

These fields all exist, and if I strip out the SQL and run the query seperately in SQL Manager, it works...

Any thoughts?

If I profile the server, it seems it tries to use the sp_executesql stored procedure, and it seems to be THAT that is having the issues... — Martin Milan
– Martin Milan, Commented May 3, 2016 at 15:23

Void Ray · Accepted Answer · 2016-05-03 16:51:02Z

You are just missing some spaces in the SQL query. Try:

 var trains = conn.Query<Train, Driver, Train>( "Select T.TrainId,T.OperatorId,T.TrainDescriptor,T.DriverId,TD.TrainDriverId,TD.Name,TD.Salary from trains as T" + " Inner Join TrainDrivers as TD on (T.DriverId = TD.TrainDriverId)" + " Where T.TrainId = @id", (t, td) => { t.Driver = td; return t; }, new { id = id }, null, true, "TrainDriverId");

Thanks... That, together with changing some of the fields in the projection, seems to have done the trick...

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