Question

I have recently come across a very simple Typed DataTable (without using a .XSD)(I’ve lost author’s URL so I can’t credit him) but it looks like there’s a lot of duplicated code (Such as the Add/Remove/GetNewRow methods).

I’ve tried to push the repetitive methods into a super class, but I have issues due to the Employee needing to be generic. I was hoping to get StackOverflow’s collective hive mind to suggest some ideas to clean this up? (If it’s even possible at all?)

using System;
using System.Data;
using System.Collections;
using System.Data.SqlClient;

namespace TypedDataSet {

  public class Employees : DataTable {
    protected SqlDataAdapter _adapter;

    public Employees() {
      string connectionString = TypedDataSet.Properties.Settings.Default.ConnectionString;
      _adapter = new System.Data.SqlClient.SqlDataAdapter("SELECT Id, Firstname, Surname FROM Employee", connectionString);
      _adapter.Fill(this);
    }

    public Employee this[int index] {
      get { return (Employee)Rows[index]; }
    }

    public void Add(Employee row) {
      Rows.Add(row);
    }

    public void Remove(Employee row) {
      Rows.Remove(row);
    }

    public Employee GetNewRow() {
      Employee row = (Employee)NewRow();
      return row;
    }

    protected override DataRow NewRowFromBuilder(DataRowBuilder builder) {
      return new Employee(builder);
    }

    public IEnumerator GetEnumerator() {
        return Rows.GetEnumerator();
    }

    protected override Type GetRowType() {
        return typeof(Employee);
    }
  }

  public class Employee : DataRow {
    internal Employee(DataRowBuilder builder)
      : base(builder) {
    }

    public Int64 Id {
      get { return (Int64)base["Id"]; }
      set { base["Id"] = value; }
    }

    public string FirstName {
      get { return (string)base["Firstname"]; }
      set { base["Firstname"] = value; }
    }

    public string Surname {
      get { return (string)base["Surname"]; }
      set { base["Surname"] = value; }
    }
  }
}

Answer 1

I believe that I’ve answered my question, kind of. I’ve had to use .net 4.0 to get the results that I was hoping for specificially the dynamic type.

So changing the existing class in the question:

Employee.cs

using System;
using System.Data;
using System.Collections;
using System.Data.Common;

namespace TypedDataSet {

  public class Employees : BaseModel<Employee> {

    public Employees(bool loadAll) {
        DbDataAdapter adapter = base.Adapter("SELECT * FROM Employees");
        adapter.Fill(this);
    }

    protected override DataRow NewRowFromBuilder(DataRowBuilder builder) {
        return new Employee(builder);
    }
  }

  public class Employee : DataRow {
    internal Employee(DataRowBuilder builder)
      : base(builder) {
    }

    public Int64 Id {
      get { return (Int64)base["Id"]; }
      set { base["Id"] = value; }
    }

    public string FirstName {
      get { return (string)base["Firstname"]; }
      set { base["Firstname"] = value; }
    }

    public string Surname {
      get { return (string)base["Surname"]; }
      set { base["Surname"] = value; }
    }
  }
}

---

And now introducing BaseModel that the above class inherits

---

BaseModel.cs

using System;
using System.Data;
using System.Collections;
using System.Data.Common;
using System.Data.SqlClient;

namespace TypedDataSet {

    public class BaseModel<T> : DataTable {
        protected DbDataAdapter _adapter;
        protected string _connectionString = TypedDataSet.Properties.Settings.Default.ConnectionString;

        public BaseModel() {
        }

        protected DbDataAdapter Adapter(string sql) {
            _adapter = new System.Data.SqlClient.SqlDataAdapter(sql, _connectionString);
            SqlCommandBuilder cb = new SqlCommandBuilder((SqlDataAdapter)_adapter);
            return _adapter; 
        }

        public dynamic this[int index] {
            get { return Rows[index]; }
        }

        public void Add(dynamic row) {
            Rows.Add(row);
        }

        public void Remove(dynamic row) {
            Rows.Remove(row);
        }

        public void Save() {
            _adapter.Update(this);
            this.AcceptChanges();
        }

        public dynamic GetNewRow() {
            dynamic row = (dynamic)NewRow();
            return row;
        }

        public IEnumerator GetEnumerator() {
            return Rows.GetEnumerator();
        }

        protected override Type GetRowType() {
            return typeof(T);
        }
    }
}

---

Which allows me to consume the class using the following code:

---

Employees employees = new Employees(true);

Employee employee = employees.GetNewRow();
employee.FirstName = "Greg";
employee.Surname = "Focker";
employees.Add(employee);

employees.Save();

foreach (Employee e in employees) {
  Console.WriteLine(e.FirstName + ' ' + e.Surname);
}

I hope to evolve this further overtime so future StackOverflow users if you’re interested in this little project take a look at http://bitbucket.org/Mozketo/typeddataset/ where I hope to host the code.