C＃設置屬性

Question

我嘗試用水印

public partial class ModernBox : Form 
{ 
    public const int WM_NCLBUTTONDOWN = 0xA1; 
    public const int HT_CAPTION = 0x2; 

    [DllImportAttribute("user32.dll")] 
    public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam); 
    [DllImportAttribute("user32.dll")] 
    public static extern bool ReleaseCapture(); 

    private const int WM_NCHITTEST = 0x84; 
    private const int HTCLIENT = 0x1; 
    private const int HTCAPTION = 0x2; 

    static Color ColorMain = Color.FromArgb(42, 42, 44); 
    static Color ColorTransparent = Color.Transparent; 

    Panel p_bro = new Panel{Visible = false}; 
    Panel p_auth = new Panel{Visible = false}; 
    WaterMarkTextBox textBox1;// = new WaterMarkTextBox{Location = new Point(10,40),Visible = true,Width = 200}; 
    WaterMarkTextBox textBox2 = new WaterMarkTextBox{ 

    Location = new Point(10,70),Visible = true,Width = 200,WaterMark = "123"}; 

    protected override void WndProc(ref Message message) 
    { 
     base.WndProc(ref message); 

     if (message.Msg == WM_NCHITTEST && (int)message.Result == HTCLIENT) 
      message.Result = (IntPtr)HTCAPTION; 
    } 

    public ModernBox() 
    { 
     InitializeComponent(); 

     panel1.MouseMove += (o, e) => { 
       if (e.Button == MouseButtons.Left) { 
        ReleaseCapture(); 
        SendMessage(Handle, WM_NCLBUTTONDOWN, HT_CAPTION, 0); 
       } 
      }; 

     panel1.BackColor = ColorMain; 

     this.StartPosition = FormStartPosition.CenterScreen; 
     this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle; 
     this.Width = 600; 
     this.Height = 400; 

     p_bro.Controls.Add(Program.presentation.webBrowser1); 
     Program.presentation.webBrowser1.Location = new Point(10,-70); 
     Program.presentation.webBrowser1.Height = 560; 
     p_bro.Location = new Point(0,30); 

     //this.Focus(); 
     this.textBox1 = new WaterMarkTextBox{Location = new Point(10,40),Visible = true,Width = 400,WaterMark = "mark",Tip = "tip"}; 
     this.textBox1.PerformLayout(); 
     //textBox1.WaterMark = "wm1"; 
     //textBox1.Tip = "tip1"; 

     this.Controls.Add(p_bro); 
     this.Controls.Add(p_auth); 
     this.Controls.Add(this.textBox1); 
     this.Controls.Add(textBox2); 

     //ModeAuth(); 
     //ModeBro(); 
    } 

    public void ModeBro() 
    { 
     p_auth.Hide(); 
     p_bro.Show(); 

     Program.presentation.webBrowser1.BringToFront(); 

     p_bro.MouseHover += (o, e) => { Program.presentation.webBrowser1.Focus(); }; 
     p_bro.AutoScroll = false; 
     p_bro.HorizontalScroll.Enabled = false; 
     p_bro.HorizontalScroll.Visible = false; 
     p_bro.Width = Program.presentation.webBrowser1.Width; 
     p_bro.Height = Program.presentation.webBrowser1.Height-50; 

     this.Width = p_bro.Width;//Program.presentation.webBrowser1.Width; 
     this.Height = p_bro.Height-5;//Program.presentation.webBrowser1.Height-20; 
    } 

    public void ModeAuth() 
    { 
     p_bro.Hide(); 
     p_auth.Show(); 

     this.Width = 600; 
     this.Height = 400; 
    } 

    private void BtnClose_Click(object sender, EventArgs e) 
    { 
     this.Close(); 
    } 

    private void BtnMaximize_Click(object sender, EventArgs e) 
    { 
     if(this.WindowState != FormWindowState.Minimized) 
     this.WindowState = FormWindowState.Maximized; 
     else 
     this.WindowState = FormWindowState.Normal; 
    } 

    private void BtnMinimaze_Click(object sender, EventArgs e) 
    { 
     this.WindowState = FormWindowState.Minimized; 
    } 
} 

public class WaterMarkTextBox : TextBox 
{ 
    ToolTip TTip = new ToolTip(); 

    private string _WaterMark; 
    public string WaterMark 
    { 
     get { return _WaterMark; } 
     set { _WaterMark = value; } 
    } 

    private string _Tip; 
    public string Tip 
    { 
     get { return _Tip; } 
     set { _Tip = value; } 
    } 

    public WaterMarkTextBox() 
    { 
     this.ForeColor = SystemColors.GrayText; 
     //if(WaterMark==null) MessageBox.Show("fail"); 

     this.Text = _WaterMark; 
     this.Leave += new System.EventHandler(this._Leave); 
     this.Enter += new System.EventHandler(this._Enter); 
     this.MouseHover += new EventHandler(WaterMarkTextBox_MouseHover); 
    } 

    private void _Leave(object sender, EventArgs e) 
    { 
     if (this.Text.Length == 0) 
     { 
      this.Text = _WaterMark; 
      this.ForeColor = SystemColors.GrayText; 
     } 
    } 

    private void _Enter(object sender, EventArgs e) 
    { 
     //MessageBox.Show(_WaterMark); 
     if (this.Text == _WaterMark) 
     { 
      this.Text = ""; 
      this.ForeColor = SystemColors.WindowText; 
     } 
    } 

    private void WaterMarkTextBox_MouseHover(object sender, EventArgs e) 
    { 
     if (Tip != null) 
      TTip.Show(Tip, this, 0, (int)(this.Height * 1.2), 2000); 
    } 
} 

使用文本框，正如你所看到的水印不會出現，在構造WaterMark和Tip價值NULL。

但它的工作原理點擊

後罰款。

我需要做些什麼來解決這個問題？

VS 2010

Answer 1

你是混合構造與初始化。該生產線

this.textBox1 = new WaterMarkTextBox{Location = new Point(10,40),Visible = true,Width = 400,WaterMark = "mark",Tip = "tip"}; 

相當於這樣的

var temp = new WaterMarkTextBox(); 
temp.Location = new Point(10,40); 
temp.Visible = true; 
temp.Width = 400; 
temp.WaterMark = "mark"; 
temp.Tip = "tip"; 
this.textBox1 = temp; 

正如你所看到的，Watermark屬性構造函數調用（第一行）之後分配。 如果你需要它的構造函數中，然後做一個構造函數參數

public WaterMarkTextBox(string watermark) 
{ 
    Watermark = watermark; 
    // ... 
} 

或處理Watermark屬性setter。

編輯：從你的評論我看你還是不明白。好了，你原來的代碼實際上是一個構造函數調用+屬性分配

this.textBox1 = new WaterMarkTextBox() {Location = new Point(10,40),Visible = true,Width = 400,WaterMark = "mark",Tip = "tip"}; 

注意()的{前 - 這是實際的構造函數調用，只是C＃允許省略（但仍然是那裏）。如果你改變了構造類似的建議，該行成爲編輯

前

this.textBox1 = new WaterMarkTextBox("mark") {Location = new Point(10,40),Visible = true,Width = 400,Tip = "tip"}; 

但要注意我的回答的最後部分或處理Watermark屬性setter。

屬性設定器不僅用於設置後臺字段。您遇到的問題是由於您的Watermark屬性設置器的錯誤實施引起的。因此，以太使它只讀（移除setter）並將值傳遞給構造函數，或者，如果它確實需要讀寫，則保留無參數構造函數並正確實現setter。像這樣的東西

public class WaterMarkTextBox : TextBox 
{ 
    ToolTip TTip = new ToolTip(); 

    private string _WaterMark = string.Empty; 
    public string WaterMark 
    { 
     get { return _WaterMark; } 
     set 
     { 
      if (value == null) value = string.Empty; 
      if (_WaterMark == value) return; 
      _WaterMark = value; 
      if (this.DesignMode || this.ContainsFocus) return; 
      this.Text = _WaterMark; 
      this.ForeColor = SystemColors.GrayText; 
     } 
    } 

    private string _Tip; 
    public string Tip 
    { 
     get { return _Tip; } 
     set { _Tip = value; } 
    } 

    public WaterMarkTextBox() 
    { 
     this.Leave += new System.EventHandler(this._Leave); 
     this.Enter += new System.EventHandler(this._Enter); 
     this.MouseHover += new EventHandler(WaterMarkTextBox_MouseHover); 
    } 

    private void _Leave(object sender, EventArgs e) 
    { 
     if (this.Text.Length == 0) 
     { 
      this.Text = _WaterMark; 
      this.ForeColor = SystemColors.GrayText; 
     } 
    } 

    private void _Enter(object sender, EventArgs e) 
    { 
     if (this.Text == _WaterMark) 
     { 
      this.Text = ""; 
      this.ForeColor = SystemColors.WindowText; 
     } 
    } 

    private void WaterMarkTextBox_MouseHover(object sender, EventArgs e) 
    { 
     if (Tip != null) 
      TTip.Show(Tip, this, 0, (int)(this.Height * 1.2), 2000); 
    } 
}