Inheriting from DataRow

Inheriting from DataRow

• AndyJ_PS

  Yep, check my example code below.  You must create a DataTable companion with an overloaded NewRowFromBuilder method.  As the DataRow must be created via NewRow:

   /// <summary>
   /// Pop3 message header
   /// </summary>
   public class Pop3MessageHeader : DataRow
   {
    Pop3MessageHeaderTable parent;

    /// <summary>
    /// CTor
    /// </summary>
    /// <param name="rowBuilder">Row builder object to use when building this row</param>
    internal Pop3MessageHeader(DataRowBuilder rowBuilder) : base(rowBuilder)
    {
     parent = (Pop3MessageHeaderTable)this.Table;
    }

    public long Number
    {
     get
     {
      return (long)this[parent.NumberColumn];
     }
     set
     {
      this[parent.NumberColumn] = value;
     }
    }

    public long Bytes
    {
     get
     {
      return (long)this[parent.BytesColumn];
     }
     set
     {
      this[parent.BytesColumn] = value;
     }
    }

    public string Subject
    {
     get
     {
      return (string)this[parent.SubjectColumn];
     }
     set
     {
      this[parent.SubjectColumn] = value;
     }
    }

    public string To
    {
     get
     {
      return (string)this[parent.ToColumn];
     }
     set
     {
      this[parent.ToColumn] = value;
     }
    }

    public string ID
    {
     get
     {
      return (string)this[parent.IDColumn];
     }
     set
     {
      this[parent.IDColumn] = value;
     }
    }

    public DateTime Date
    {
     get
     {
      return (DateTime)this[parent.DateColumn];
     }
     set
     {
      this[parent.DateColumn] = value;
     }
    }

    public string From
    {
     get
     {
      return (string)this[parent.FromColumn];
     }
     set
     {
      this[parent.FromColumn] = value;
     }
    }

    public bool Attachments
    {
     get
     {
      return (bool)this[parent.AttachmentsColumn];
     }
     set
     {
      this[parent.AttachmentsColumn] = value;
     }
    } 
   }

   /// <summary>
   /// Pop 3 message table
   /// </summary>
   public class Pop3MessageHeaderTable : DataTable
   {
    DataColumn numberColumn;
    DataColumn bytesColumn;
    DataColumn subjectColumn;
    DataColumn toColumn;
    DataColumn idColumn;
    DataColumn dateColumn;
    DataColumn fromColumn;
    DataColumn attachmentsColumn;

    public Pop3MessageHeaderTable()
    {
     subjectColumn = new DataColumn("Subject",typeof(System.String), null, MappingType.Element);
     Columns.Add(subjectColumn);

     toColumn = new DataColumn("To",typeof(System.String), null, MappingType.Element);
     Columns.Add(toColumn);

     idColumn = new DataColumn("ID",typeof(System.String), null, MappingType.Element);
     Columns.Add(idColumn);

     dateColumn = new DataColumn("Date",typeof(DateTime), null, MappingType.Element);
     Columns.Add(dateColumn);

     fromColumn = new DataColumn("From",typeof(System.String), null, MappingType.Element);
     Columns.Add(fromColumn);

     numberColumn = new DataColumn("Number",typeof(long), null, MappingType.Element);
     Columns.Add(numberColumn);

     bytesColumn = new DataColumn("Bytes",typeof(long), null, MappingType.Element);
     Columns.Add(bytesColumn);

     attachmentsColumn = new DataColumn("Attachments",typeof(bool), null, MappingType.Element);
     Columns.Add(attachmentsColumn);
    }

    public DataColumn AttachmentsColumn
    {
     get
     {
      return attachmentsColumn;
     }
    }

    public DataColumn NumberColumn
    {
     get
     {
      return numberColumn;
     }
    }

    public DataColumn BytesColumn
    {
     get
     {
      return bytesColumn;
     }
    }

    public DataColumn SubjectColumn
    {
     get
     {
      return subjectColumn;
     }
    }

    public DataColumn ToColumn
    {
     get
     {
      return toColumn;
     }
    }

    public DataColumn IDColumn
    {
     get
     {
      return idColumn;
     }
    }

    public DataColumn DateColumn
    {
     get
     {
      return dateColumn;
     }
    }

    public DataColumn FromColumn
    {
     get
     {
      return fromColumn;
     }
    }

    /// <summary>
    /// Indexer of this strong typed list
    /// </summary>
    public Pop3MessageHeader this[int index]
    {
     get
     {
      return ((Pop3MessageHeader)(this.Rows[index]));
     }
    }

    /// <summary>
    /// Creates a new typed row
    /// </summary>
    /// <param name="rowBuilder">supplied row builder to pass to the typed row</param>
    /// <returns>the new typed datarow</returns>
    protected override DataRow NewRowFromBuilder(DataRowBuilder rowBuilder)
    {
     return new Pop3MessageHeader(rowBuilder);
    }

    /// <summary>
    /// Return the type of the typed datarow
    /// </summary>
    /// <returns>returns the requested type</returns>
    protected override Type GetRowType()
    {
     return typeof(Pop3MessageHeader);
    } 
   }
  }
  

  
  

• Ibrahim Hamouda

  Thank you!
  

• _Gerry_

  I'm missing something. What is the purpose of a RowBuilder - to initialize the row's item values to some defaults, or to provide the typed and appropriately named accessors that go from name-to-ordinal of the item[]

  
  

• Nisa

  public class MyDataRow : DataRow
  {
      public MyDataRow(DataRowBuilder builder)
          : base(builder)
      {
      }

      // your code here

  }

  
  

• kangalert

  DataRowBuilder cannot be instantiated from code
  

• Lawrence 007

  No problem, glad to help! 
  
• Inheriting from DataRow