Winform 水印TextBox

方法一：

public partial class WaterTextBox : TextBox

   {

       private readonly Label lblwaterText = new Label();



       public WaterTextBox()

       {

           InitializeComponent();

           lblwaterText.BorderStyle = BorderStyle.None;

           lblwaterText.Enabled = false;

           lblwaterText.BackColor = Color.White;

           lblwaterText.AutoSize = false;

           lblwaterText.Top = 1;

           lblwaterText.Left = 0;

           Controls.Add(lblwaterText);

       }



       [Category("扩展属性"), Description("显示的提示信息")]

       public string WaterText

       {

           get { return lblwaterText.Text; }

           set { lblwaterText.Text = value; }

       }



       public override string Text

       {

           set

           {

               if (value != string.Empty)

                   lblwaterText.Visible = false;

               else

                   lblwaterText.Visible = true;

               base.Text = value;

           }

           get { return base.Text; }

       }



       protected override void OnSizeChanged(EventArgs e)

       {

           if (Multiline && (ScrollBars == ScrollBars.Vertical || ScrollBars == ScrollBars.Both))

               lblwaterText.Width = Width - 20;

           else

               lblwaterText.Width = Width;

           lblwaterText.Height = Height - 2;

           base.OnSizeChanged(e);

       }



       protected override void OnEnter(EventArgs e)

       {

           lblwaterText.Visible = false;

           base.OnEnter(e);

       }



       protected override void OnLeave(EventArgs e)

       {

           if (base.Text == string.Empty)

               lblwaterText.Visible = true;

           base.OnLeave(e);

       }

   }

方法二：（待改进）改进点：提示文本是颜色，进入时自动消失，失去焦点后如果没有值又显示提示文本。如果哪位改进好了，可以回给我看看吗？

public partial class WaterTextBox1 : TextBox

    {

        private String strEmptyValue = String.Empty;



        public WaterTextBox1()

        {

            InitializeComponent();

            processDefaultValue();

        }



        public String EmptyValue //记录空值的表现

        {

            get { return strEmptyValue; }

            set

            {

                if (base.Text == strEmptyValue)

                    base.Text = value.Trim();

                strEmptyValue = value.Trim();

                processDefaultValue();

            }

        }



        public override string Text //覆盖Text属性

        {

            get { return base.Text.Trim() == strEmptyValue.Trim() ? String.Empty : base.Text.Trim(); }

            set

            {

                base.Text = value;

                processDefaultValue();

            }

        }



        protected override void OnVisibleChanged(EventArgs e)

        {

            base.OnVisibleChanged(e);

            processDefaultValue();

        }



        protected override void OnMouseClick(MouseEventArgs e)

        {

            base.OnMouseClick(e);

            if (base.Text == strEmptyValue)

            {

                SelectAll();

            }



        }



        protected override void OnValidating(CancelEventArgs e) //覆盖TextBox验证处理

        {

            processDefaultValue();

            base.OnValidating(e);

        }



        private void processDefaultValue() //处理表现空值的方法

        {

            base.Text = base.Text.Trim().Length <= 0 ? strEmptyValue : base.Text.Trim();

        }

    }