Question

I have a 2 classes:

• Employee
• EmployeeDetails

I have methods like this for Employee class:

public static Employee LoadEmployee(int id)
{
    StringBuilder selectQuery = new StringBuilder();

    string selectQuery = " my query with the parameter 'Id' ";
    dbGenerator _db = dbGenerator.Instance.Database;

    DbCommand selectCommand = _db.GetSqlStringCommand(selectQuery.ToString());
    _db.AddInParameter(selectCommand, "@id", System.Data.DbType.String, Id);

    //EXECUTE THE COMMAND
    using (IDataReader dr = _db.ExecuteReader(selectCommand))
    {
        if (dr.Read())
        {
            result = new Employee();
            Employee.LoadDataReader(result, dr);
        }

        dr.Close();
    }

    return result;
}

And I have a method doing the same thing with the EmployeeDetails class … no change at all except the return type.

I am sure there are ways to minimize the lines of code and also using the C# generics it will more readable and generics provide type safety without the overhead of multiple implementations.

I need a method in which I can pass the class object, selectQuery, ParameterId like this

public static <T> LoadData<T>(Object object, string selectQuery, int paramId)
{
    // do stuff 

    // return <T>results;
}

Any suggestion would be appreciated.

Answer 1

The others’ suggestions of just using an ORM are great, but if you have a good reason for doing this layer from scratch, you could amend your design to look something like this:

public class Employee 
{
    public virtual void InitFromDataReader(DataReader dr) { }
}

public class EmployeeDetails : Employee
{
    public override void InitFromDataReader(DataReader dr) { }
}

public static TEmployee LoadEmployee<TEmployee>(int id) where TEmployee : Employee, new()
{
    using (DataReader dr = new DataReader()) 
    {
        var result = new TEmployee();
        result.InitFromDataReader(dr);
        return result;
    }
}

The main constraint is that you need to have a no-args constructor on your entity objects, otherwise the LoadEmployee methods can’t create them correctly. That is, unless you explicitly pass a factory object as a parameter to the method.