Dapper.NET and stored proc with multiple result sets

Question

Is there any way to use Dapper.NET with stored procs that return multiple result sets?

In my case, the first result set is a single row with a single column; if it's 0 then the call was successful, and the second result set will contain that actual rows/columns of data. (and if it was non-zero, an error occured and no second result set will be provided)

Any chance to handle this with Dapper.NET? So far, I'm only ever getting back that single 0 - but nothing more.

Update: OK, it works fine - as long as the result set no. 2 is a single entity:

Dapper.SqlMapper.GridReader reader = 
    _conn.QueryMultiple("sprocname", dynParams, 
    commandType: CommandType.StoredProcedure);

int status = reader.Read<int>().FirstOrDefault();
MyEntityType resultObj = reader.Read<MyEntityType>().FirstOrDefault();

Now, I have yet another requirement.

Dapper's multi-mapping (splitting up a single row returned from SQL Server into two separate entities) for that second result set doesn't seem to be supported as of yet (at least there doesn't seem to be an overload of .Read<T> that can handle multi-mapping).

How can I get split that row into two entities?

Answer 1

QueryMultiple supports the ability to deal with multiple result sets. The only design restriction we added was totally disabling buffering for the grid reader. This means the whole API is streaming.

In the simplest case you can use:

var grid = connection.QueryMultiple("select 1 select 2");
grid.Read<int>().First().IsEqualTo(1);
grid.Read<int>().First().IsEqualTo(2);

In the slightly more sophisticated case you can do crazy stuff like this:

var p = new DynamicParameters();
p.Add("a", 11);
p.Add("r", dbType: DbType.Int32, direction: ParameterDirection.ReturnValue);

connection.Execute(@"create proc #spEcho
@a int
as 
begin

select @a Id, 'ping' Name, 1 Id, 'pong1' Name
select @a Id, 'ping' Name, 2 Id, 'pong2' Name
return @a
end");

var grid = connection.QueryMultiple("#spEcho", p, 
                                     commandType: CommandType.StoredProcedure);

var result1 = grid.Read<dynamic, dynamic, Tuple<dynamic, dynamic>>(
                  (a, b) => Tuple.Create((object)a, (object)b)).ToList();
var result2 = grid.Read<dynamic, dynamic, Tuple<dynamic, dynamic>>(
                  (a, b) => Tuple.Create((object)a, (object)b)).ToList();

((int)(result1[0].Item1.Id)).IsEqualTo(11);
((int)(result1[0].Item2.Id)).IsEqualTo(1);

((int)(result2[0].Item1.Id)).IsEqualTo(11);
((int)(result2[0].Item2.Id)).IsEqualTo(2);

p.Get<int>("r").IsEqualTo(11);

You'll need to add this using statement to enable QueryMultiple .

using Dapper; /* to add extended method QueryMultiple public static GridReader QueryMultiple(this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null); */