构造函数中的C＃set属性未按预期顺序

Question

I try use textbox with watermark

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);
    }
}

As you can see watermark not appear, in constructor WaterMark and Tip value are NULL .

But it works fine after click

.

What do I need to do to fix this?

VS 2010

Answer 1

You are mixing the constructor with initializer . The line

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

is equivalent to something like this

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;

As you can see, the Watermark property is assigned after the constructor call (the first line). If you need it inside the constructor, then make a constructor with parameters

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

or handle the Watermark property setter.

EDIT: From your comment I see you still don't understand. Ok, so your original code is actually a constructor call + property assignments

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

Note the () before the { - this is the actual constructor call, just C# allows to omit that (but still it's there). If you change the constructor like suggested, that line becomes

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

But note the last part of my answer before the edit

or handle the Watermark property setter.

Property setters are not just for setting the backing fields. The problem you are experiencing is caused by the incorrect implementation of your Watermark property setter. So, ether make it read only (remove the setter) and pass the value to the constructor, or, if it really needs to be read write, then keep the parameterless constructor and implement the setter correctly. Something like this

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);
    }
}