如何：用BindingSource将Windows Forms控件绑定到工厂对象

Posted 2021-05-22 清语堂

在构建与数据交互的控件时，有时会发现有必要将控件绑定到生成其他对象的对象或方法。这样的对象或方法称为工厂。例如，您的数据源可能是方法调用的返回值，而不是内存或类型中的对象。您可以将控件绑定到这种数据源，只要该源返回一个集合即可。

您可以使用BindingSource控件轻松地将控件绑定到工厂对象。

例子

下面的示例演示如何通过使用BindingSource控件将DataGridView控件绑定到工厂方法。工厂方法名为 GetOrdersByCustomerId，它将在Northwind数据库中返回给定客户的所有订单。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}

 

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        // This is the TextBox for entering CustomerID values.
        private TextBox customerIdTextBox = new TextBox();

        // This is the DataGridView that displays orders for the
        // specified customer.
        private DataGridView customersDataGridView = new DataGridView();

        // This is the BindingSource for binding the database query
        // result set to the DataGridView.
        private BindingSource ordersBindingSource = new BindingSource();

        public Form1()
        {
            // Set up the CustomerID TextBox.
            this.customerIdTextBox.Location = new Point(100, 200);
            this.customerIdTextBox.Size = new Size(500, 30);
            this.customerIdTextBox.Text =
                "Enter a valid Northwind CustomerID, for example: ALFKI," +
                " then RETURN or click outside the TextBox";
            this.customerIdTextBox.Leave +=
                new EventHandler(customerIdTextBox_Leave);
            this.customerIdTextBox.KeyDown +=
                new KeyEventHandler(customerIdTextBox_KeyDown);
            this.Controls.Add(this.customerIdTextBox);

            // Set up the DataGridView.
            customersDataGridView.Dock = DockStyle.Top;
            this.Controls.Add(customersDataGridView);

            // Set up the form.
            this.Size = new Size(800, 500);
            this.Load += new EventHandler(Form1_Load);
        }

        // This event handler binds the BindingSource to the DataGridView
        // control\'s DataSource property.
        private void Form1_Load(
            System.Object sender,
            System.EventArgs e)
        {
            // Attach the BindingSource to the DataGridView.
            this.customersDataGridView.DataSource =
                this.ordersBindingSource;
        }

        // This is a static factory method. It queries the Northwind
        // database for the orders belonging to the specified
        // customer and returns an IEnumerable.
        public static IEnumerable GetOrdersByCustomerId(string id)
        {
            // Open a connection to the database.
            string connectString = "Integrated Security=SSPI;" +
                "Persist Security Info=False;Initial Catalog=Northwind;" +
                "Data Source= localhost";
            SqlConnection connection = new SqlConnection();

            connection.ConnectionString = connectString;
            connection.Open();

            // Execute the query.
            string queryString =
                String.Format("Select * From Orders where CustomerID = \'{0}\'",
                id);
            SqlCommand command = new SqlCommand(queryString, connection);
            SqlDataReader reader =
                command.ExecuteReader(CommandBehavior.CloseConnection);
            return reader;
        }

        // These event handlers are called when the user tabs or clicks
        // out of the customerIdTextBox or hits the return key.
        // The database is then queried with the CustomerID
        //  in the customerIdTextBox.Text property.
        void customerIdTextBox_Leave(object sender, EventArgs e)
        {
            // Attach the data source to the BindingSource control.
            this.ordersBindingSource.DataSource =
                GetOrdersByCustomerId(this.customerIdTextBox.Text);
        }

        void customerIdTextBox_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Return)
            {
                // Attach the data source to the BindingSource control.
                this.ordersBindingSource.DataSource =
                    GetOrdersByCustomerId(this.customerIdTextBox.Text);
            }
        }
    }
}