C#/Winform 自定义控件-可以调节尺寸的TextBox

效果

1.创建控件

在当前项目右击 -> 添加 -> 用户控件，命名为SizableTextBox

2.添加TextBox和Lable控件

3.功能实现

F7进入代码

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

namespace WinFormsApp1
{
    public partial class SizableTextBox : UserControl
    {
        private bool handleClick;

        public SizableTextBox()
        {
            InitializeComponent();

            InitTextBox();
            InitHandle();
            InitComp();
        }

        #region 初始化
        // 初始化控件
        private void InitComp()
        {
            this.Size = new Size(
                lableHandle.Location.X + lableHandle.Width, textBox.Height);
        }

        // 初始化TextBox
        private void InitTextBox()
        {
            textBox.Location = new Point(0, 0);
        }

        // 初始化手柄
        private void InitHandle()
        {
            // 尺寸位置
            lableHandle.Text = "";
            lableHandle.AutoSize = false;
            lableHandle.Size = new Size(8, 8);
            lableHandle.Location = new Point(
                textBox.Width - 4, (textBox.Height / 2) - 4);

            // 显示
            lableHandle.Visible = false;
            lableHandle.FlatStyle = FlatStyle.Flat;
            lableHandle.BorderStyle = BorderStyle.FixedSingle;
            lableHandle.Cursor = Cursors.SizeWE;

            // 事件
            textBox.Enter += new EventHandler(TextBox_Enter);
            textBox.Leave += new EventHandler(TextBox_Leave);
            lableHandle.MouseDown += new MouseEventHandler(Handle_MouseDown);
            lableHandle.MouseMove += new MouseEventHandler(Handle_MouseMove);
            lableHandle.MouseUp += new MouseEventHandler(Handle_MouseUp);
        }

        #endregion

        #region 事件
        // 点击TextBox时显示
        private void TextBox_Enter(object sender, EventArgs e)
        {
            lableHandle.Visible = true;
        }

        // 点击其他控件时隐藏
        private void TextBox_Leave(object sender, EventArgs e)
        {
            lableHandle.Visible = false;
        }

        // 手柄点击
        private void Handle_MouseDown(object sender, MouseEventArgs e)
        {
            handleClick = true;
        }

        // 手柄移动
        private void Handle_MouseMove(object sender, MouseEventArgs e)
        {
            if (handleClick)
            {
                textBox.Size = new Size(
                    textBox.Size.Width + e.X, textBox.Size.Height);

                this.Size = new Size(
                    textBox.Size.Width + 4, this.Size.Height);

                lableHandle.Location = new Point(
                    textBox.Location.X + textBox.Size.Width - 4, lableHandle.Location.Y);
            }
        }

        // 手柄松开
        private void Handle_MouseUp(object sender, MouseEventArgs e)
        {
            handleClick = false;
        }
        #endregion
    }
}

4.使用控件

生成 → 重新生成解决方案

拖动SizableTextBox到窗口或用户控件即可使用