关于VS2005 DataGridView的一个问题

Question

private void btnGetData_Click(object sender, EventArgs e)
        {
            SqlConnection conn = new SqlConnection("Server=(local);Integrated Security=SSPI;Initial Catalog=Northwind");
            conn.Open();
            DataSet da = new DataSet();
            SqlDataAdapter custDa = new SqlDataAdapter("select * from Customers", conn);
            SqlDataAdapter ordersdAa = new SqlDataAdapter("select * from Orders", conn);
            custDa.Fill(da, "Customers");
            ordersdAa.Fill(da, "Orders");
            DataRelation dr = new DataRelation("CustOrders", da.Tables["Customers"].Columns["CustomerID"], da.Tables["Orders"].Columns["CustomerID"]);
            da.Relations.Add(dr);
            dgCustomers.DataSource = da;
            dgCustomers.DataMember = "Customers";
            dgOrders.DataSource = da;
            dgOrders.DataMember = "Customers.CustOrders";
            BindingContext [dgCustomers .DataSource ,"Customers"].CurrentChanged+=new EventHandler(frmAdvGridBinding_CurrentChanged);
        }        private void frmAdvGridBinding_CurrentChanged(object sender, EventArgs e)
        {
            CurrencyManager cm = (CurrencyManager)BindingContext[dgCustomers.DataSource, "Customers"];
            DataRowView drv = (DataRowView)cm.Current;
            //dgOrders.CaptionText = string.Format("{0}is order history", drv["ContactName"]);
    
        }
问题1:CurrencyManager cm = (CurrencyManager)BindingContext[dgCustomers.DataSource, "Customers"];系统提示值不能为空？？使用new创建新的实例？？
问题2：在vs2005ZO中DataGridView的CaptionText在窗体属性中怎么找不到？？或者还是如何设置？

Answer 1

to 问题1:CurrencyManager cm = (CurrencyManager)BindingContext[dgCustomers.DataSource, "Customers"];系统提示值不能为空？？使用new创建新的实例？？看看这句话是否在绑定之前触发的