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("擴展屬性"), Description("顯示的提示信息")] 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:(待改進)改進點:提示文本是顏色,進入時自動消失,失去焦點後如果沒有值又顯示提示文本。如果哪位改進好了,可以回給我看看嗎?
public partial class WaterTextBox1 : TextBox { private String strEmptyValue = String.Empty; public WaterTextBox1() { InitializeComponent(); processDefaultValue(); } public String EmptyValue //記錄空值的表現 { get { return strEmptyValue; } set { if (base.Text == strEmptyValue) base.Text = value.Trim(); strEmptyValue = value.Trim(); processDefaultValue(); } } public override string Text //覆蓋Text屬性 { 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) //覆蓋TextBox驗證處理 { processDefaultValue(); base.OnValidating(e); } private void processDefaultValue() //處理表現空值的方法 { base.Text = base.Text.Trim().Length <= 0 ? strEmptyValue : base.Text.Trim(); } }