使用VB.Net的GhostText

Question

Hello guys, I tried to create a ghost text using Labels over the Textboxes. I am using VB.Net2005. I accomplished this with this code:

Public Class frmDataEntry

    Private Sub PhantomTextLastName()
        If txtLastName.Text = "" Then
            lblLastName.Visible = True
        Else
            lblLastName.Visible = False
        End If
    End Sub

    Private Sub PhantomTextFirstName()
        If txtFirstName.Text = "" Then
            lblFirstName.Visible = True
        Else
            lblFirstName.Visible = False
        End If
    End Sub

    Private Sub PhantomTextMiddleInitial()
        If txtMiddleInitial.Text = "" Then
            lblMiddleInitial.Visible = True
        Else
            lblMiddleInitial.Visible = False
        End If
    End Sub

    Private Sub txtLastName_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtLastName.Click
        lblLastName.Text = "Last Name"
    End Sub

    Private Sub txtLastName_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles txtLastName.KeyDown
        PhantomTextLastName()
    End Sub

    Private Sub txtLastName_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtLastName.TextChanged
        PhantomTextLastName()
    End Sub

    Private Sub lblLastName_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblLastName.Click
        txtLastName.Focus()
    End Sub

    Private Sub txtFirstName_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtFirstName.Click
        lblFirstName.Text = "First Name"
    End Sub

    Private Sub txtFirstName_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles txtFirstName.KeyDown
        PhantomTextFirstName()
    End Sub

    Private Sub txtFirstName_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtFirstName.TextChanged
        PhantomTextFirstName()
    End Sub

    Private Sub lblFirstName_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblFirstName.Click
        txtFirstName.Focus()
    End Sub

    Private Sub lblMiddleInitial_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblMiddleInitial.Click
        txtMiddleInitial.Focus()
    End Sub

    Private Sub txtMiddleInitial_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtMiddleInitial.Click
        lblMiddleInitial.Text = "Middle I."
    End Sub

    Private Sub txtMiddleInitial_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles txtMiddleInitial.KeyDown
        PhantomTextMiddleInitial()
    End Sub

    Private Sub txtMiddleInitial_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtMiddleInitial.TextChanged
        PhantomTextMiddleInitial()
    End Sub
End Class

Is there any way to reduce this code, so that when I try to add another Textboxes I'll never have to retype a bunch of codes. I have basic knowledge n using Module and Class but I really don't have any idea on how to apply this with this project. I am a newbie, and if you have any tutorial that could help me solve this problem, kindly give me d link. Thanks in advance & God bless.

Answer 1

Create a usercontrol . The code behind your usercontrol might be something like:

 Public Class GhostTextbox

    Private _ghostText As String
    Public Property GhostText As String
        Get
            Return _ghostText
        End Get
        Set(ByVal Value As String)
            _ghostText = Value
        End Set
    End Property

    Public Property ActualText As String
        Get
            Return Me.TextBox1.Text
        End Get
        Set(ByVal Value As String)
            Me.TextBox1.Text = Value
        End Set
    End Property

    Private Sub PhantomText()
        If TextBox1.Text = "" Then
            Label1.Visible = True
        Else
            Label1.Visible = False
        End If
    End Sub

    Private Sub TextBox1_Click(sender As Object, e As System.EventArgs) Handles TextBox1.Click
        Label1.Text = GhostText
    End Sub

    Private Sub TextBox1_KeyDown(sender As Object, e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
        PhantomText()
    End Sub

    Private Sub TextBox1_TextChanged(sender As System.Object, e As System.EventArgs) Handles TextBox1.TextChanged
        PhantomText()
    End Sub

    Private Sub GhostTextbox_Load(sender As Object, e As System.EventArgs) Handles Me.Load
        Label1.Text = GhostText
    End Sub
End Class

Then, use this custom control instead of just a TextBox . All you need to do is set the GhostText property for each new control you add instead of redoing the same logic over again.

Answer 2

You can put more than 1 Handler in 1 Sub, just separate them by a ,

For example:

Private Sub txtMiddleInitial_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtMiddleInitial.TextChanged
    PhantomTextMiddleInitial()
End Sub

Private Sub txtFirstName_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtFirstName.TextChanged
    PhantomTextFirstName()
End Sub

Private Sub txtLastName_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtLastName.TextChanged
    PhantomTextLastName()
End Sub

To:

Private Sub txtControl_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtLastName.TextChanged, txtFirstName.TextChanged, txtMiddleInitial.TextChanged
    PhantomTextLastName()
End Sub

and so on

MSDN: Connect Multiple Events to a Single Event Handler in Windows Forms

Answer 3

I've used a NativeWindow class to do this:

Public Class WaterMark
  Inherits NativeWindow

  <DllImport("User32.dll")> _
  Public Shared Function GetWindowDC(ByVal hWnd As IntPtr) As IntPtr
  End Function

  <DllImport("user32.dll")> _
  Private Shared Function ReleaseDC(ByVal hWnd As IntPtr, ByVal hDC As IntPtr) As Boolean
  End Function

  Private _TextBox As TextBox
  Private _EmptyMessage As String

  Private Const WM_PAINT As Integer = &HF

  Public Sub New(ByVal textBox As TextBox, ByVal emptyMessage As String)
    _TextBox = TextBox
    AddHandler _TextBox.TextChanged, AddressOf OnTextChanged
    _EmptyMessage = emptyMessage
    MyBase.AssignHandle(textBox.Handle)
  End Sub

  Private Sub OnTextChanged(ByVal sender As Object, ByVal e As EventArgs)
    If _TextBox.Text = String.Empty Then
      _TextBox.Invalidate()
    End If
  End Sub

  Public Overrides Sub ReleaseHandle()
    RemoveHandler _TextBox.TextChanged, AddressOf OnTextChanged
    MyBase.ReleaseHandle()
  End Sub

  Protected Overrides Sub WndProc(ByRef m As Message)
    MyBase.WndProc(m)
    If m.Msg = WM_PAINT AndAlso _TextBox.Text = String.Empty Then
      Dim dc As IntPtr = GetWindowDC(m.HWnd)
      Using g As Graphics = Graphics.FromHdc(dc)
        TextRenderer.DrawText(g, _EmptyMessage, _TextBox.Font, _TextBox.ClientRectangle, Color.Gray, Color.Empty, TextFormatFlags.Left Or TextFormatFlags.VerticalCenter)
      End Using
      ReleaseDC(m.HWnd, dc)
    End If
  End Sub
End Class

Then I just need to attach the TextBox to it:

Private _WaterMark As WaterMark

Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
  _WaterMark = New WaterMark(TextBox1, "Enter Something:")
End Sub