How do I execute RAW SQL query and dump it to JSON in ASP.NET MVC 5 (EF 6)? - sql

Question

I want to execute a raw SQL query as shown below:
select material, method, count(*)
from treatment
group by material, method
and return it as a JSON object.
Because EF 6 allows the execution of raw query (i.e., Database.SQLQuery()), I use it to create a JSON Object.
My code looks like this.
// GET: Dummy
public string Dummy()
{
string query = "select material, method, count(*) as cnt from Treatment "
+ " group by material, method";
var result = db.Database.SqlQuery<List<String>>(query);
var jsonResult = JsonConvert.SerializeObject(result);
return jsonResult;
}
However, instead of getting a JSON object with the material and methods, I get an empty json object instead.
[[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[]]
Is it possible to return the correct JSON object without having the model for the the raw query? If so, how to update my code to return the correct result?
Thanks in advance

Answer 1

You can't resolve that query to a list of strings, you need to resolve it to a (list of) class(es), like this :
public static string Dummy()
{
using (var db = new TestDbEntities())
{
string query = "select 'material' as material , 'method' as method, 1 as cnt ";
var result = db.Database.SqlQuery<MyClass>(query);
var res = result.ToList();
var jsonResult = JsonConvert.SerializeObject(res);
return jsonResult;
}
}
where your class will be something like this :
public class MyClass
{
public string Material { get; set; }
public string Method { get; set; }
public int Cnt { get; set; }
}

Answer 2

You need to capture query result sets with multiple columns using a class with matching property names (make sure they have exactly same name and proper casing) and parameterless constructor:
public string Dummy()
{
string query = "select material as Material, method as Method, count(*) as Cnt from Treatment group by material, method";
var result = db.Database.SqlQuery<ResultSet>(query).ToList();
var jsonResult = JsonConvert.SerializeObject(result);
return jsonResult;
}
public class ResultSet
{
public string Material { get; set; }
public string Method { get; set; }
public int Cnt { get; set; }
}
Note that Database.SqlQuery<T> will return an IEnumerable<T> with type System.Data.Entity.Internal.InternalSqlQuery<T>, so that a List<string> is not fit in this context. If you just return single result set, Database.SqlQuery<string>(...).ToList() should be used instead of Database.SqlQuery<List<string>>.
Similar issue:
Entity framework raw SQL Query

Answer 3

Use FOR JSON AUTO:
string query = "select material, method, count(*) as cnt from Treatment "
+ " group by material, method FOR JSON AUTO";