Question

I’ve written an app that I use as an agent to query data from a database and automatically load it into my distributed web cache.

I do this by specifying an sql query and a type in a configuration. The code that actually does the querying looks like this:

List<Object> result = null; try { result = dc.ExecuteQuery(elementType, entry.Command).OfType<Object>().ToList(); } catch (Exception ex) { HandleException(ex, WebCacheAgentLogEvent.DatabaseExecutionError); continue; } 

elementType is a System.Type created from the type specified in the configuration (using Type.GetType()), and entry.Command is the SQL query.

The specific entity type I’m having an issue with looks like this:

public class FooCount {     [Column(Name = 'foo_id')]     public Int32 FooId { get; set; }      [Column(Name = 'count')]     public Int32 Count { get; set; } } 

The SQL query looks like this:

select foo_id as foo_id, sum(count) as [count] from foo_aggregates group by foo_id order by foo_id 

For some reason, when the query is executed, the ‘Count’ property ends up populated, but not the ‘FooId’ property. I tried running the query myself, and the correct column names are returned, and the column names match up with what I’ve specified in my mapping attributes. Help!

Answer 1

This is insane…

What fixed my problem was decorating my entity class with TableAttribute:

[Table(Name = 'foo_aggregates')] public class FooCount {     [Column(Name = 'foo_id')]     public Int32 FooId { get; set; }      [Column(Name = 'count')]     public Int32 Count { get; set; } } 

I had assumed (wrongly, apparently) that since I wasn’t using the GetTable<T>() method, I didn’t need the corresponding mapping attribute.

Update: A year and a half later, it finally dawned on me it seems like the ColumnAttribute decorations on the properties are ignored unless there’s a corresponding TableAttribute decoration on the class. This explains why the ‘Count’ property was getting populated, since its naming would match the column in the SQL statement, whereas FooId/foo_id of course do not match.