Question

是否可以在Visual Studio中创建一个文本框，如下所示：

Answer 1

实际上。更好的解决方案是使用文本框的Paint事件来绘制字符串。

以下是代码：

class CueTextBox : TextBox
{
    public event EventHandler CueTextChanged;
    private string _cueText;

    public string CueText
    {
        get { return _cueText; }
        set
        {
            value = value ?? string.Empty;
            if (value != _cueText)
            {
                _cueText = value;
                OnCueTextChanged(EventArgs.Empty);
            }
        }
    }

    public CueTextBox()
        : base()
    {
        _cueText = string.Empty;
    }

    protected virtual void OnCueTextChanged(EventArgs e)
    {
        this.Invalidate(true);
        if (this.CueTextChanged != null)
            this.CueTextChanged(this, e);
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);

        if (string.IsNullOrEmpty(this.Text.Trim()) && !string.IsNullOrEmpty(this.CueText) && !this.Focused)
        {
            Point startingPoint = new Point(0, 0);
            StringFormat format = new StringFormat();
            Font font = new Font(this.Font.FontFamily.Name, this.Font.Size, FontStyle.Italic);
            if (this.RightToLeft == RightToLeft.Yes)
            {
                format.LineAlignment = StringAlignment.Far;
                format.FormatFlags = StringFormatFlags.DirectionRightToLeft;
            }
            e.Graphics.DrawString(CueText, font, Brushes.Gray, this.ClientRectangle, format);
        }
    }

    const int WM_PAINT = 0x000F;
    protected override void WndProc(ref Message m)
    {
        base.WndProc(ref m);
        if (m.Msg == WM_PAINT)
        {
            this.OnPaint(new PaintEventArgs(Graphics.FromHwnd(m.HWnd), this.ClientRectangle));
        }
    }
}

现在，您只需要将'CueText'属性设置为您想要的初始值，然后就完成了！

Answer 2

您只需处理三个TextBox事件，在Designer中将TextBox的文本设置为“username”并将其设置为Font Italics，然后将TextBox BackColor设置为LightYellow，其余部分由Event处理程序处理...

     private void textBox1_TextChanged(object sender, EventArgs e)
    {
        if (textBox1.Text == "")
            ChangeTextBoxtoWatermark();
    }

    private void textBox1_MouseEnter(object sender, EventArgs e)
    {
        if (textBox1.Text == "username")
        {
            textBox1.Text = "";
            textBox1.Font = new Font(this.Font, FontStyle.Regular);
            textBox1.BackColor = Color.White;
        }
    }

    private void textBox1_MouseLeave(object sender, EventArgs e)
    {
        if (textBox1.Text == "")
            ChangeTextBoxtoWatermark();
    }

    private void ChangeTextBoxtoWatermark()
    {
        textBox1.Font = new Font(this.Font, FontStyle.Italic);
        textBox1.BackColor = Color.LightYellow;
        textBox1.Text = "username";
    }

我检查过它并且运行正常:)）

Answer 3

这通常被称为“提示”。

There is a good answer on SO。
此外，如果您使用的是DevExpress WinForms，我写了a small class to enhance their TextEdit control。

自定义文本框控件

3 个答案: