C# join DataTable (support Left/Right/Full join)转贴

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

using System.Data;

namespace JoinDataTable

{

    public partial class frmMain : Form

    {

        DataTable table1 = null;

        DataTable table2 = null;

        public frmMain()

        {

            InitializeComponent();

            table1 = new DataTable();

            table1.Columns.Add("symbol", typeof(string));

            table1.Columns.Add("side", typeof(int));

            table1.Columns.Add("qty", typeof(int));

            table1.Rows.Add(new object[] { "HSI", -1, 9000});

            table1.Rows.Add(new object[] { "TOPIX", 1, 2000 });

            dataGridView1.DataSource = table1.DefaultView;

            table2 = new DataTable();

            table2.Columns.Add("symbol", typeof(string));

            table2.Columns.Add("side", typeof(int));

            table2.Columns.Add("qty", typeof(int));

            table2.Rows.Add(new object[] { "HSI", 1, 6000 });

            table2.Rows.Add(new object[] { "AEX", -1, 5000 });

            dataGridView2.DataSource = table2.DefaultView;

            DataTable t3 = Join(table1, table2,

                new DataColumn[] { table1.Columns[0]},

                new DataColumn[] { table2.Columns[0]},

                true, true);

            dataGridView3.DataSource = t3.DefaultView;

        }

        private DataTable Join(DataTable left, DataTable right,

            DataColumn[] leftCols, DataColumn[] rightCols,

            bool includeLeftJoin, bool includeRightJoin)

        {

            DataTable result = new DataTable("JoinResult");

            using (DataSet ds = new DataSet())

            {

                ds.Tables.AddRange(new DataTable[] { left.Copy(), right.Copy() });

                DataColumn[] leftRelationCols = new DataColumn[leftCols.Length];

                for (int i = 0; i < leftCols.Length; i++)

                    leftRelationCols[i] = ds.Tables[0].Columns[leftCols[i].ColumnName];

                DataColumn[] rightRelationCols = new DataColumn[rightCols.Length];

                for (int i = 0; i < rightCols.Length; i++)

                    rightRelationCols[i] = ds.Tables[1].Columns[rightCols[i].ColumnName];

                //create result columns

                for (int i = 0; i < left.Columns.Count; i++)

                    result.Columns.Add(left.Columns[i].ColumnName, left.Columns[i].DataType);

                for (int i = 0; i < right.Columns.Count; i++)

                {

                    string colName = right.Columns[i].ColumnName;

                    while (result.Columns.Contains(colName))

                        colName += "_2";

                    result.Columns.Add(colName, right.Columns[i].DataType);

                }

                //add left join relations

                DataRelation drLeftJoin = new DataRelation("rLeft", leftRelationCols, rightRelationCols, false);

                ds.Relations.Add(drLeftJoin);

                //join

                result.BeginLoadData();

                foreach (DataRow parentRow in ds.Tables[0].Rows)

                {

                    DataRow[] childrenRowList = parentRow.GetChildRows(drLeftJoin);

                    if (childrenRowList != null && childrenRowList.Length > 0)

                    {

                        object[] parentArray = parentRow.ItemArray;

                        foreach (DataRow childRow in childrenRowList)

                        {

                            object[] childArray = childRow.ItemArray;

                            object[] joinArray = new object[parentArray.Length + childArray.Length];

                            Array.Copy(parentArray, 0, joinArray, 0, parentArray.Length);

                            Array.Copy(childArray, 0, joinArray, parentArray.Length, childArray.Length);

                            result.LoadDataRow(joinArray, true);

                        }

                    }

                    else //left join

                    {

                        if (includeLeftJoin)

                        {

                            object[] parentArray = parentRow.ItemArray;

                            object[] joinArray = new object[parentArray.Length];

                            Array.Copy(parentArray, 0, joinArray, 0, parentArray.Length);

                            result.LoadDataRow(joinArray, true);

                        }

                    }

                }

                if (includeRightJoin)

                {

                    //add right join relations

                    DataRelation drRightJoin = new DataRelation("rRight", rightRelationCols, leftRelationCols, false);

                    ds.Relations.Add(drRightJoin);

                    foreach (DataRow parentRow in ds.Tables[1].Rows)

                    {

                        DataRow[] childrenRowList = parentRow.GetChildRows(drRightJoin);

                        if (childrenRowList == null || childrenRowList.Length == 0)

                        {

                            object[] parentArray = parentRow.ItemArray;

                            object[] joinArray = new object[result.Columns.Count];

                            Array.Copy(parentArray, 0, joinArray,

                                joinArray.Length - parentArray.Length, parentArray.Length);

                            result.LoadDataRow(joinArray, true);

                        }

                    }

                }

                result.EndLoadData();

            }

            return result;

        }

        private void button1_Click(object sender, EventArgs e)

        {

        }

    }

}