IEnumerables in Mighty

All methods in Mighty which return an IEnumerable (or an IAsyncEnumerable for async) of data do no database access at all until you start to enumerate the enumerable:

var depts = new MightyOrm(connectionString, "Department", "DepartmentID");

// No database access happens here, instead a contract to perform the database access is returned to you
depts.All(new { Location = "London" });

// The actual database access starts here, i.e. when you start to use the contract you have been given
foreach (var dept in depts)
{
    Console.WriteLine(dept.Name);
}

This only applies to methods which return IEnumerable (the variants of Query, QueryMultiple and All). All the other database access methods in Mighty (Insert, Update, Save, all the variants of Execute, etc.) do all their database access before returning.

If your own method needs to return results directly rather than a contract to provide results (or more generally if you need to force database access to happen by a certain point in your code) then call .ToList() on the results. But be aware that this will allocate memory for a new list object containing all the results, before doing anything else with them, and so is probably not what you want for large result sets.

Here is a more complete example showing this. (This example also uses strong types, but strong types are not required for the .ToList() trick to work.)

public class Department
{
    public string Name { get; set; }
    public string Location { get; set; }
}

// There is no database access left to do once this has finished - what is returned is just a list!
public IEnumerable<Department> GetDepartmentsByLocation(string Location)
{
    // No database access happens here
    MightyOrm<Department> db = new MightyOrm<Department>();

    // Select all database rows where Location = @Location
    // All of the database access has finished once .ToList() has completed
    return db.All(new { Location }).ToList();
}

You can apply this to return an IEnumerable from Mighty from a .NET API call. The API framework won’t accept the IEnumerable directly from Mighty, but will accept the different IEnumerable produced after applying .ToList().