Question

I want to use a SQL query in Entity Framework.

Here is my code:

 string sql = (@"SELECT G.GainId,
                (SELECT Name FROM Carrier WHERE CarrierId = G.CarrierId) AS Carrier,
                (SELECT Name + ' ' + Surname FROM [User] WHERE UserId = G.GainerId) AS Gainer,
                (SELECT Name + ' ' + Surname FROM [User] WHERE UserId = G.GiverId) AS Giver,
                (SELECT Name + ' ' + Surname FROM [User] WHERE UserId = G.CustomerId) AS Customer,
                    P.Name,
                    G.Gained,
                    G.Paid
                    FROM Gain AS G 
                    INNER JOIN Product AS P ON P.ProductId = G.ProductId");

            DataTable tbl = _context.Database.SqlQuery<DataTable>(sql) as DataTable;

But tbl is null. Do you have any suggestions? I am new with Entity Framework.

Answer 1

That’s because SqlQuery is not meant to return a DataTable. It’s built to return your entity types as an IEnumerable<T> where T is your entity type. Use the below statement and remember that it’s an enumerable type that’s being returned. Now perform with it what you need.

var tbl = _context.Database.SqlQuery<{your entity type}>(sql)

Edited

Yes, in fact you can very easily build this type. In fact, because the query seems so isolated you could probably build a private class inside of the class it’s executed in so that how I’ll build the example. However, that’s something you need to decide. Below I’ll give you a template for the class. The two properties with ?? I don’t know exactly what type they correlate to so you’ll need to plug those in.

private class QueryResult
{
    public int GainId { get; set; }
    public string Carrier { get; set; }
    public string Gainer { get; set; }
    public string Giver { get; set; }
    public string Customer { get; set; }
    public string Name { get; set; }
    public ?? Gained { get; set; }
    public ?? Paid { get; set; }
}

And then issue the statement like this…

var tbl = _context.Database.SqlQuery<QueryResult>(sql)