父子表关联在窗体中的绑定显示和浏览

     private BindingManagerBase bm1 = null;
        private BindingManagerBase bm2 = null;

        private void DataScanInForm2_Load(object sender, EventArgs e)
        {
            string sqlString1 = "select * from 客户";
            string sqlString2 = "select * from 订单";
            string[] sqlStrings = new string[] { sqlString1, sqlString2 };
            string[] tableNames = new string[] { "客户", "订单" };

            DataSet ds = new DataSet();
            ds = Rabbit.DBUtility.DBHelperOLEDB.Query(sqlStrings, tableNames);

            DataColumn parentColumn = new DataColumn();
            DataColumn childColumn = new DataColumn();
            parentColumn = ds.Tables["客户"].Columns["ID"];
            childColumn = ds.Tables["订单"].Columns["客户 ID"];

            DataRelation relation = new DataRelation("每一位客户的订单", parentColumn, childColumn);
            ds.Relations.Add(relation);

            //绑定
            txtCID.DataBindings.Add("text", ds, "客户.ID");
            txtCCompany.DataBindings.Add("text", ds, "客户.公司");
            txtCFamliyName.DataBindings.Add("text", ds, "客户.姓氏");
            txtCHomepage.DataBindings.Add("text", ds, "客户.主页");

            txtOID.DataBindings.Add("text", ds, "客户.每一位客户的订单.订单 ID");
            dtpODate.DataBindings.Add("value", ds, "客户.每一位客户的订单.订单日期");
            txtOName.DataBindings.Add("text", ds, "客户.每一位客户的订单.发货名称");
            txtOCity.DataBindings.Add("text", ds, "客户.每一位客户的订单.发货城市");
            nudOCost.DataBindings.Add("value", ds, "客户.每一位客户的订单.运费");

            Binding bTax = new Binding("text", ds, "客户.每一位客户的订单.税款");
            bTax.Format += new ConvertEventHandler(bTax_Format);
            txtOTax.DataBindings.Add(bTax);
           

            bm1 = this.BindingContext[ds, "客户"];
            bm2 = this.BindingContext[ds, "客户.每一位客户的订单"];
            bm1.PositionChanged += new EventHandler(bm1_PositionChanged);
            bm2.PositionChanged += new EventHandler(bm2_PositionChanged);
            this.bm1_PositionChanged(null, new EventArgs());
            this.bm2_PositionChanged(null, new EventArgs());
        }

        private void bTax_Format(object sender, ConvertEventArgs e)
        {
            e.Value = string.Format("{0:c3}", (decimal)e.Value);
        }

        private void bm1_PositionChanged(object sender, EventArgs e)
        {
            textBox1.Text = string.Format("当前位置：{0}，共计：{1}", bm1.Position + 1, bm1.Count);
            this.bm2_PositionChanged(null, new EventArgs());
        }

        private void bm2_PositionChanged(object sender, EventArgs e)
        {
            //当bm1.Position改变时，先执行bm2.Position的PositionChanged事件，
            //再执行bm1.Position的PositionChanged事件。而在执行bm2.Position的
            //PositionChanged事件之前，bm2.Position已经指向了bm1.Position所指向
            //记录的第一个子记录，即bm2.Position=0；如果没有子记录，则bm2.Position=-1
            textBox2.Text = string.Format("当前位置：{0}，共计：{1}", bm2.Position + 1, bm2.Count);
        }

        private void btnCBack_Click(object sender, EventArgs e)
        {
            if (bm1.Position > 0)
            {
                bm1.Position -= 1;
            }
        }

        private void btnCNext_Click(object sender, EventArgs e)
        {
            if (bm1.Position < bm1.Count - 1)
            {
                bm1.Position += 1;
            }
        }

        private void btnCFirst_Click(object sender, EventArgs e)
        {
            bm1.Position = 0;
        }

        private void btnCLast_Click(object sender, EventArgs e)
        {
            bm1.Position = bm1.Count - 1;
        }

        private void btnOBack_Click(object sender, EventArgs e)
        {
            if (bm2.Position > 0)
            {
                bm2.Position -= 1;
            }
        }

        private void btnONext_Click(object sender, EventArgs e)
        {
            if (bm2.Position < bm2.Count - 1)
　　　　　　　{

　　　　　　　　　　//当下一记录的数据无法通过与之绑定的控件的有效性检验时，
　　　　　　　　 //将会导致指向下一记录失败，即下式计算失败，bm2.Position保持不变
               //例如，图中有一个显示运费的NumericUpDown控件，如果下一记录的运费
               //为300，而该控件的MaxValue属性值为200，则将会导致指向失败

                bm2.Position += 1;
            }
        }

        private void btnOFirst_Click(object sender, EventArgs e)
        {
            bm2.Position = 0;
        }

        private void btnOLast_Click(object sender, EventArgs e)
        {
            bm2.Position = bm2.Count - 1;
        }