Create DataRelation ship between two tables

 There is a simple demo for DataRelation class of DataSet.

while u can use DataTable.Select(conditions) or DataView.Filter to filete the data what you want .however,maybe the method is more complex with this one.

        datatalbe performance test#region datatalbe performance test

        /**//// <summary>
        /// Test table relation.
        /// </summary>
        public void Relation()
        ...{
            DataTable dtParent = this.CreateDataTable();
            dtParent.TableName = "Parent";

            .net framework 2.0#region .net framework 2.0
            DataSet ds = new DataSet();
            ds.Tables.Add(dtParent);
            DataRelation relations = ds.Relations.Add("Relation", ds.Tables["Parent"].Columns["index"], ds.Tables["Parent"].Columns["parent_index"], false);

            foreach (DataRow row in ds.Tables["Parent"].Rows)
            #endregion

            .net framework 1.1#region .net framework 1.1
            //DataRelation relations = new DataRelation("Relation", dtParent.Columns["index"], dtParent.Columns["parent_index"], false);
            //foreach (DataRow row in dtParent.Rows)
            #endregion
            ...{
                if (0 != string.Compare(row["parent_index"].ToString(), "0", true,System.Globalization.CultureInfo.CurrentCulture))
                ...{
                    continue;
                }

                this.DebugPrint(string.Format("{0}", row["description"].ToString()));

                this.PrintChilds(row, relations);

                this.DebugPrint("--------------------------------------------------");

                
            }
        }

        /**//// <summary>
        /// print the child 
        /// </summary>
        private void PrintChilds(DataRow rowParent, DataRelation relations)
        ...{
            DataRow[] rowChilds = rowParent.GetChildRows(relations);

            if (null == rowChilds || 0 == rowChilds.Length)
            ...{
                return;
            }

            string spaces = string.Empty;
            foreach (DataRow row in rowChilds)
            ...{
                spaces = spaces.PadLeft(int.Parse(row["layer"].ToString()), ' ');
                this.DebugPrint(string.Format("{0}|-- {1}", spaces, row["description"].ToString()));

                this.PrintChilds(row, relations);                
            }
        }

        /**//// <summary>
        /// Create the datatable for test.
        /// </summary>
        /// <returns></returns>
        private DataTable CreateDataTable()
        ...{
            DataTable dt = new DataTable("Test");

            // add columns
            dt.Columns.Add(new DataColumn("index", typeof(Int32)));
            dt.Columns.Add(new DataColumn("parent_index", typeof(Int32)));
            dt.Columns.Add(new DataColumn("description", typeof(string)));
            dt.Columns.Add(new DataColumn("layer", typeof(string)));

            // add rows
            dt.Rows.Add(new object[] ...{ 1000, 0,     "first 1" , 0});
            dt.Rows.Add(new object[] ...{ 1001, 1000, "secord 2", 1 });
            dt.Rows.Add(new object[] ...{ 2000, 0, "third 3", 0 });
            dt.Rows.Add(new object[] ...{ 2001, 1000, "forth 4", 2 });
            dt.Rows.Add(new object[] ...{ 3000, 2000, "fifth 5", 1 });
            dt.Rows.Add(new object[] ...{ 3001, 3000, "six 6", 2 });
            dt.Rows.Add(new object[] ...{ 2222, 0, "seven 7", 0 });


            dt.Rows.Add(new object[] ...{ 100, 2222, "first 11", 1 });
            dt.Rows.Add(new object[] ...{ 101, 1000, "secord 21", 1 });
            dt.Rows.Add(new object[] ...{ 200, 222, "third 31", 3 });
            dt.Rows.Add(new object[] ...{ 201, 1001, "forth 41", 2 });
            dt.Rows.Add(new object[] ...{ 300, 2000, "fifth 51", 1 });
            dt.Rows.Add(new object[] ...{ 301, 3000, "six 61", 2 });
            dt.Rows.Add(new object[] ...{ 222, 1000, "seven 71", 3 });

            // accept changes
            dt.AcceptChanges();

            //DataSet ds = new DataSet("Test");
            //ds.Tables.Add(dt);

            return dt;
        }

        private void DebugPrint(string msg)
        ...{
            //System.Diagnostics.Debug.WriteLine(msg);
            Console.WriteLine(msg);
        }
        #endregion