来自文本框的 Web 控件 - 不保存 Postaback 上的新属性

Question

我觉得自己是个白痴，它应该这么简单，但似乎不起作用。下面是我的控制代码。

Imports System.Web.UI.WebControls
Public Class PasswordTextBox
            Inherits TextBox
Public Sub New()
    TextMode = TextBoxMode.Password
End Sub
Public Property Password As String
    Get
        Dim s As String = CType(ViewState("Password"), String)
        If s Is Nothing Then Return ""
        Return s
    End Get
    Set(value As String)
        ViewState("Password") = value
    End Set
End Property
Private Const DEFAULT_PASSWORD As String = "********************"
Public Overrides Property Text() As String
    Get
        If Password = "" Then Return ""
        Return DEFAULT_PASSWORD
    End Get
    Set
        MyBase.Text = DEFAULT_PASSWORD
        Attributes("value") = DEFAULT_PASSWORD
    End Set
End Property
Protected Overrides Sub OnPreRender(e As EventArgs)
    MyBase.OnPreRender(e)
    Attributes("value") = Text
End Sub
Protected Overrides Sub Render(ByVal output As System.Web.UI.HtmlTextWriter)
    MyBase.Render(output)
End Sub

结束类

目的很简单，覆盖属性以始终将 ***** 显示为值，而是使用新属性 Password 来获取/设置数据。因此，当用户从浏览器中使用"检查元素"功能时，他无法获得实际密码。

但是，在页面回发时，当我获得 txtPassword.Password 属性时，它会返回一个空字符串。

我错过了什么吗？谢谢

Answer 1

好的，我能够找到问题。我必须从 IPostBackDataHandler 继承，然后覆盖 LoadPostData 方法。

新类如下所示。

Imports System.Web.UI
Imports System.Web.UI.WebControls

Public Class PasswordTextBox
      Inherits TextBox
      Implements IPostBackDataHandler
Public Sub New()
    TextMode = TextBoxMode.Password
End Sub
Public Property Password As String
    Get
        Dim s As String = CType(ViewState("Password"), String)
        If s Is Nothing Then Return ""
        Return s
    End Get
    Set(value As String)
        ViewState("Password") = value
    End Set
End Property
Private Const DEFAULT_PASSWORD As String = "********************"
Public Overrides Property Text() As String
    Get
        If Password = "" Then Return ""
        Return DEFAULT_PASSWORD
    End Get
    Set
        MyBase.Text = DEFAULT_PASSWORD
        Attributes("value") = DEFAULT_PASSWORD
    End Set
End Property
Protected Overrides Sub OnPreRender(e As EventArgs)
    MyBase.OnPreRender(e)
    Attributes("value") = Text
End Sub
Protected Overrides Sub Render(ByVal output As System.Web.UI.HtmlTextWriter)
    MyBase.Render(output)
End Sub
Public Overridable Shadows Function LoadPostData(postDataKey As String, postCollection As System.Collections.Specialized.NameValueCollection) As Boolean Implements IPostBackDataHandler.LoadPostData
    Dim presentValue As String = Password
    Dim postedValue As String = postCollection(postDataKey)
    If presentValue Is Nothing OrElse Not presentValue.Equals(postedValue) Then
        If postedValue <> DEFAULT_PASSWORD Then Password = postedValue
        Return True
    End If
    Return False
End Function
End Class