WinForm程序中的类TextBox的自定义控件, 添加失去焦点的功能

原理:

一、在控件的后台代码中, 添加布尔类型的属性CanFocus

二、在控件的构造函数中, 注册Enter事件的处理方法. 并在处理方法中,根据CanFocus属性的值来决定是否可以丢失焦点, 如果可以则调用Windows消息的发送类.

三、在处理方法中,调用User32.dll类库, 发送window消息.

示例代码:

//Windows消息的发送方法

//WMMessageHepler.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace YXT.Common
{
    public class WMMessageHepler
    {
        private const int WM_KILLFOCUS = 0x0008;

        //发送失去焦点的Window消息
        public static void SendBlurMsg(IntPtr hWnd)
        {
            PostMessage(hWnd, WM_KILLFOCUS, 0, 0);
        }

        [DllImport("user32.dll")]
        private static extern void PostMessage(IntPtr hWnd, int msg, int wParam, int lParam);

        [DllImport("User32.dll", EntryPoint = "SendMessage")]
        private static extern int SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, string lParam);
    }
}

//自定义控件的关键代码

//WatermarkTextBox.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using YXT.Common;

namespace YXT.Client.Controls
{
    [ToolboxBitmap(typeof(TextBox))]
    public class WatermarkTextBox : TextBox
    {

        public WatermarkTextBox()
        {
            this.BorderStyle = BorderStyle.FixedSingle;
            this.Enter += new EventHandler(WatermarkTextBox_Enter);
        }

        void WatermarkTextBox_Enter(object sender, EventArgs e)
        {
            if (this.SetBlur)
            {
                this.OnBlur();
            }
        }

        private Color _borderColor = Color.Red;
        private string _watermarkTitle;
        private Color _watermarkColor = Color.DarkGray;
        private bool _setBlur = false;

        /// <summary>
        /// 控件是否失去焦点
        /// </summary>
        public bool SetBlur
        {
            get { return this._setBlur; }
            set
            {
                this._setBlur = value;
                Invalidate();
            }
        }

        /// <summary>
        /// 水印字体提示
        /// </summary>
        public string WatermarkTitle
        {
            get { return _watermarkTitle; }
            set
            {
                _watermarkTitle = value;
                Invalidate();
            }
        }

        /// <summary>
        /// 边框颜色
        /// </summary>
        public Color BorderColor
        {
            get { return _borderColor; }
            set
            {
                _borderColor = value;
                Invalidate();
            }
        }

        /// <summary>
        /// 水印颜色
        /// </summary>
        public Color WatermarkColor
        {
            get { return _watermarkColor; }
            set
            {
                _watermarkColor = value;
                Invalidate();
            }
        }

        private void OnBlur()
        {
            WMMessageHepler.SendBlurMsg(this.Handle);
        }

        protected override void WndProc(ref Message m)
        {

            base.WndProc(ref m);
            if (m.Msg == 0xf || m.Msg == 0x14 || m.Msg == 0x85)
            {
                if (this.BorderStyle == BorderStyle.FixedSingle)
                {
                    using (Graphics g = Graphics.FromHwnd(this.Handle))
                    {
                        using (var pen = new Pen(_borderColor))
                        {
                            g.DrawRectangle(pen, 0, 0, this.Width - 1, this.Height - 1);
                            WmPaint(ref m);
                        }
                    }
                }
            }
        }

        private void WmPaint(ref Message m)
        {
            using (Graphics graphics = Graphics.FromHwnd(base.Handle))
            {
                if (Text.Length == 0
                    && !string.IsNullOrEmpty(_watermarkTitle)
                    && !Focused)
                {
                    TextFormatFlags format =
                        TextFormatFlags.EndEllipsis |
                        TextFormatFlags.VerticalCenter;

                    if (RightToLeft == RightToLeft.Yes)
                    {
                        format |= TextFormatFlags.RightToLeft | TextFormatFlags.Right;
                    }

                    TextRenderer.DrawText(
                        graphics,
                        _watermarkTitle,
                        Font,
                        base.ClientRectangle,
                        _watermarkColor,
                        format);
                }
            }
        }
    }
}

//使用示例

//方法使用示例

ControlsEdintor(string controlsName)
        {
            //控件编辑时 修改样式
            foreach (var value in this.Controls)
            {
                var textBox = value as WatermarkTextBox;
                if (controlsName == "编辑")
                {
                    if (textBox != null)
                    {
                        textBox.BorderStyle = BorderStyle.FixedSingle;
                        textBox.ReadOnly = false;
                        textBox.SetBlur = false;
                    }
                }
                else
                {
                    if (textBox != null)
                    {
                        textBox.BorderStyle = BorderStyle.None;
                        textBox.ReadOnly = true;
                        textBox.SetBlur = true;
                    }
                }
            }
        }