Programming Microsoft Visual Basic .NET/Programming Microsoft Visual Basic .NET (Microsoft Press)(X08-78517)(2002).bin/setup/vbnet/17 controls/customcontroldemo/textboxex.vb

Text File | 2002-03-16 | 8.6 KB | 257 lines

Imports System.Text.RegularExpressions
Imports System.ComponentModel
Imports System.Reflection

' an improved TextBox control

<DefaultEvent("InvalidKey")> _
Public Class TextBoxEx
    Inherits System.Windows.Forms.TextBox

    Event InvalidKey(ByVal sender As Object, ByVal e As EventArgs)

    Sub New()
        MyBase.New()
    End Sub

    '-------------------------------------------------------------------
    ' True if the field is required
    '-------------------------------------------------------------------

    <Description("True if the field is required and must contain a value"), _
             Category("Validation")> _
    Dim m_IsRequired As Boolean

    Property IsRequired() As Boolean
        Get
            Return m_IsRequired
        End Get
        Set(ByVal Value As Boolean)
            m_IsRequired = Value
        End Set
    End Property

    '-------------------------------------------------------------------
    ' The text of the message
    '-------------------------------------------------------------------

    Dim m_ErrorMessage As String

    <Description("The error message displayed in case of error"), _
         Category("Validation")> _
   Property ErrorMessage() As String
        Get
            Return m_ErrorMessage
        End Get
        Set(ByVal Value As String)
            m_ErrorMessage = Value
        End Set
    End Property

    '-------------------------------------------------------------------
    ' The BeepOnError property (defaults to True)
    '-------------------------------------------------------------------

    Dim m_BeepOnError As Boolean = True

    <Description("If True, a beep will be emitted if validation fails"), _
     DefaultValue(True)> _
    Property BeepOnError() As Boolean
        Get
            Return m_BeepOnError
        End Get
        Set(ByVal Value As Boolean)
            m_BeepOnError = Value
        End Set
    End Property

    '-------------------------------------------------------------------
    ' The ForeColor of the message
    '-------------------------------------------------------------------

    Dim m_ErrroForeColor As Color = SystemColors.ControlText

    <Description("The ForeColor of the DisplayControl in case of error"), _
     Category("Validation")> _
    Property ErrorForeColor() As Color
        Get
            Return m_ErrroForeColor
        End Get
        Set(ByVal Value As Color)
            m_ErrroForeColor = Value
        End Set
    End Property

    Sub ResetErrorForeColor()
        ErrorForeColor = SystemColors.ControlText
    End Sub

    Function ShouldSerializeErrorForeColor() As Boolean
        Debug.WriteLine("ShouldSerializeErrorForeColor for " & Me.Name)
        Return Not Me.ErrorForeColor.Equals(SystemColors.ControlText)
    End Function

    '-------------------------------------------------------------------
    ' The ValidateRegex property
    '-------------------------------------------------------------------

    <Description("The regular expression used to validate the control on exit"), _
             Category("Validation")> _
    Property ValidateRegex() As String
        Get
            Return m_ValidateRegex
        End Get
        Set(ByVal Value As String)
            ' Before setting this mask, which check that its a valid regular expression
            Try
                ' We attempt to use this mask as a regular expression
                If Value <> "" Then
                    Dim dummy As Boolean = Regex.IsMatch("abcde", Value)
                End If
                ' if no error assignment is ok
                m_ValidateRegex = Value
            Catch ex As Exception
                MessageBox.Show(ex.Message, "Invalid Property", MessageBoxButtons.OK, MessageBoxIcon.Error)
            End Try
        End Set
    End Property

    Dim m_ValidateRegex As String

    '-------------------------------------------------------------------
    ' The optional control that displays the error message
    '-------------------------------------------------------------------

    Dim m_DisplayControl As Control

    <Description("The control that will display the error message"), _
         Category("Validation")> _
    Property DisplayControl() As Control
        Get
            Return m_DisplayControl
        End Get
        Set(ByVal Value As Control)
            m_DisplayControl = Value
        End Set
    End Property

    '-------------------------------------------------------------------
    ' The type of value the control must contain
    '-------------------------------------------------------------------

    Enum ValidTypes
        Any = 0
        [Byte]
        [Short]
        [Integer]
        [Long]
        [Single]
        [Double]
        [Decimal]
        [DateTime]
    End Enum

    Dim m_ValidType As ValidTypes

    <Description("The type of value that is valid for this field"), _
     Category("Validation"), DefaultValue(ValidTypes.Any)> _
    Property ValidType() As ValidTypes
        Get
            Return m_ValidType
        End Get
        Set(ByVal Value As ValidTypes)
            m_ValidType = Value
        End Set
    End Property

    '-------------------------------------------------------------------
    ' The IsValid property
    '-------------------------------------------------------------------

    ' This property has the same semantics as the Validate method.
    ' (Just an example to show how you can hide a property.)

    <Browsable(False)> _
    ReadOnly Property IsValid() As Boolean
        Get
            Return Validate()
        End Get
    End Property

    '-------------------------------------------------------------------
    ' The Validate method
    '-------------------------------------------------------------------

    <Description("Returns True if the current value passes the validation test")> _
    Function Validate(Optional ByVal DisplayMessage As Boolean = True) As Boolean
        ' Assume control passed the validation.
        Validate = True

        ' Apply the IsRequired property.
        If Me.IsRequired And Me.Text = "" Then
            Validate = False
        End If

        ' Apply the ValidType property.
        If Validate = True And Me.Text <> "" Then
            Validate = CheckValueType(Me.Text)
        End If

        ' Apply the ValidateRegex property.
        If Validate = True And Me.ValidateRegex <> "" Then
            Validate = Regex.IsMatch(Me.Text, Me.ValidateRegex)
        End If

        ' If the validation failed, the called asked to see a message box,
        ' the client defined a display control and an error message, then show the message on the control.
        If DisplayMessage And Not (DisplayControl Is Nothing) And Me.ErrorMessage <> "" Then
            If Validate Then
                ' Delete and previous error message.
                DisplayControl.Text = ""
            Else
                ' Display error message, and enforce colors.
                DisplayControl.Text = Me.ErrorMessage
                DisplayControl.ForeColor = m_ErrroForeColor
            End If
        End If

        ' emit a beep in case of error, if so requested
        If Not Validate And Me.BeepOnError Then Beep()
    End Function

    ' Check that a value can be assigned to the value type
    Function CheckValueType(ByVal o As Object) As Boolean
        Dim res As Object
        Try
            Select Case m_ValidType
                Case ValidTypes.Byte : res = CByte(o)
                Case ValidTypes.Short : res = CShort(o)
                Case ValidTypes.Integer : res = CInt(o)
                Case ValidTypes.Long : res = CLng(o)
                Case ValidTypes.Single : res = CSng(o)
                Case ValidTypes.Double : res = CDbl(o)
                Case ValidTypes.Integer : res = CDec(o)
                Case ValidTypes.DateTime : res = CDate(o)
            End Select
            ' if we get here, the assignment was ok
            Return True
        Catch
            ' else there is an error
            Return False
        End Try
    End Function

    ' this method is called when the control is about to raise the Validating event.

    Protected Overrides Sub OnValidating(ByVal e As System.ComponentModel.CancelEventArgs)
        If Me.Validate() Then
            ' If validation is ok, let the base class fire the Validating event.
            MyBase.OnValidating(e)
        Else
            ' else, cancel the focus shift.
            e.Cancel = True
        End If
    End Sub

End Class