Question

I want to execute a single Query (or Stored Proc with multiple resultsets). I know how to do Multi-mapping using Dapper, but I can’t sort how to map the two collections onto the same parent. Basically, given this Object definition…

class ParentObject
{
    string Name { get; set; }
    ICollection<ChildObjectOne> ChildSetOne {get;set;}
    ICollection<ChildObjectTwo> ChildSetTwo { get; set; }
}

class ChildObjectOne
{
    string Name { get; set; }
}

class ChildObjectTwo
{
    int id { get; set; }
    string LocationName { get; set; }
}

I want to be able to run a Dapper query that somehow yields:

IQueryable<ParentObject> result = cnn.Query(
          // Some really awesome dapper syntax goes here
);

Answer 1

Not sure if you DON’T want to use MultiMapping but here’s how it would work for your case. As far as I know and read on SO, is not not possible to map a deep nested object graph with a simple Query.

 static void Main(string[] args)
        {
            var sqlParent = "SELECT parentId as Id FROM ParentTable WHERE parentId=1;";
            var sqlChildOneSet = "SELECT Name FROM ChildOneTable;"; // Add an appropriate WHERE
            var sqlChildTwoSet = "SELECT Id, LocationName FROM ChildTwoTable;"; // Add an appropriate WHERE

            var conn = GetConnection() // whatever you're getting connections with
            using (conn)
            {
                conn.Open();
                using (var multi = conn.QueryMultiple(sqlParent + sqlChildOneSet + sqlChildTwoSet))
                {
                    var parent = multi.Read<ParentObject>().First();
                    parent.ChildSetOne = multi.Read<ChildOne>().ToList();
                    parent.ChildSetTwo = multi.Read<ChildTwo>().ToList();
                }
            }
        }

Similar questions for nested objects and dapper :

https://stackoverflow.com/search?q=nested+objects+%2B+dapper