当内容超出范围时在文本框中显示滚动条C#答案

【问题标题】：Display scroll bar in textbox when contents are beyond the bounds C#当内容超出范围时在文本框中显示滚动条C#
【发布时间】：2010-11-27 07:50:59
【问题描述】：

是否只有当文本框中的行数大于显示的行数时才能显示/隐藏文本框中的滚动条？

【问题讨论】：

很遗憾没有。您可以将滚动条设置为水平、垂直或两者，但在必要时不显示/隐藏。
只在基本文本框中 - 试试 RichTextBox

标签： c# textbox scrollbar

【解决方案1】：

考虑使用RichTextBox——它内置了这种行为。

【讨论】：

啊，谢谢奥斯汀。有时最明显的解决方案是最好的:)
不要忘记将属性 ScrollViewer.VerticalScrollBarVisibility="Auto" 添加到 RichTextBox

【解决方案2】：

Public Class TextBoxScrollbarPlugin
    Private WithEvents mTarget As TextBox

    ''' <summary>
    ''' After the Handle is created, mTarget.IsHandleCreated always returns
    ''' TRUE, even after HandleDestroyed is fired.
    ''' </summary>
    ''' <remarks></remarks>
    Private mIsHandleCreated As Boolean = False

    Public Sub New(item As TextBox)
        mTarget = item
        mIsHandleCreated = mTarget.IsHandleCreated
    End Sub

    Private Sub Update()
        If Not mTarget.IsHandleCreated Then
            Return
        ElseIf Not mIsHandleCreated Then
            Return
        End If
        Dim textBoxRect = TextRenderer.MeasureText(mTarget.Text,
                                                   mTarget.Font,
                                                   New Size(mTarget.Width, Integer.MaxValue),
                                                   TextFormatFlags.WordBreak + TextFormatFlags.TextBoxControl)

        Try
            If textBoxRect.Height > mTarget.Height Then
                mTarget.ScrollBars = ScrollBars.Vertical
            Else
                mTarget.ScrollBars = ScrollBars.None
            End If
        Catch ex As System.ComponentModel.Win32Exception
            'this sometimes throws a "failure to create window handle"
            'error.
            'This might happen if the TextBox is unvisible and/or
            'to small to display a toolbar.
            If mLog.IsWarnEnabled Then mLog.Warn("Update()", ex)
        End Try
    End Sub

    Private Sub mTarget_HandleCreated(sender As Object, e As System.EventArgs) Handles mTarget.HandleCreated
        mIsHandleCreated = True
    End Sub

    Private Sub mTarget_HandleDestroyed(sender As Object, e As System.EventArgs) Handles mTarget.HandleDestroyed
        mIsHandleCreated = False
    End Sub

    Private Sub mTarget_SizeChanged(sender As Object, e As System.EventArgs) Handles mTarget.SizeChanged
        Update()
    End Sub

    Private Sub mTarget_TextChanged(sender As Object, e As System.EventArgs) Handles mTarget.TextChanged
        Update()
    End Sub

End Class


Private mPlugins As New List(Of Object)
Private Sub Form_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    mPlugins.Add(New TextBoxScrollbarPlugin(txtBoxOne))
    mPlugins.Add(New TextBoxScrollbarPlugin(txtBoxTwo))
    mPlugins.Add(New TextBoxScrollbarPlugin(txtBoxThree))
End Sub

【讨论】：

对于那些必须使用文本框（就像我不得不因为它是一个自定义控件）的人来说，上面的答案似乎工作正常。我假设我必须用 OR 替换 + 以使其按位，并且我以 textbox.wordwrap 值为条件设置了分词。希望有帮助。

【解决方案3】：

谢谢笨蛋，它有效！这是 c# 中虚拟答案的简短版本

在 SizeChanged 和 TextChanged 处理程序的末尾调用此代码：

Size textBoxRect = TextRenderer.MeasureText(
    this.YourTextBox.Text, 
    this.YourTextBox.Font, 
    new Size(this.YourTextBox.Width, int.MaxValue),
    TextFormatFlags.WordBreak | TextFormatFlags.TextBoxControl);
try
{
    this.YourTextBox.ScrollBars = textBoxRect.Height > this.YourTextBox.Height ? 
        ScrollBars.Vertical : 
        ScrollBars.None;
} catch (System.ComponentModel.Win32Exception)
{
     // this sometimes throws a "failure to create window handle" error.
     // This might happen if the TextBox is unvisible and/or
     // too small to display a toolbar.
}

【讨论】：

【解决方案4】：

我有 tnimas 解决方案在 vb 中工作。功能写得很好，我没有看到错误。

    Private Sub TextBoxSizeChanged(sender As Object, e As EventArgs) Handles Me.SizeChanged
    Dim textBoxRect As Size = TextRenderer.MeasureText(TextBox.Text, TextBox.Font, New Size(TextBox.Width, Integer.MaxValue), TextFormatFlags.WordBreak Or TextFormatFlags.TextBoxControl)
    Try
        TextBox.ScrollBar = If(textBoxRect.Height > TextBox.Height, ScrollBars.Vertical, ScrollBars.None)
    Catch ex As Exception
        'handle error
    End Try
End Sub

【讨论】：

【解决方案5】：

我自己尝试了 tnimas 的解决方案，但无法捕捉到异常，所以我使用 WinApi 来切换滚动条的可见状态，而不是像这样：

Size textBoxRect = TextRenderer.MeasureText(YourTextBox.Text, YourTextBox.Font, new Size(YourTextBox.Width, int.MaxValue), TextFormatFlags.WordBreak | TextFormatFlags.TextBoxControl);

WinApi.ShowScrollBar(YourTextBox.Handle, (int)WinApi.ScrollBar.SB_VERT, textBoxRect.Height > YourTextBox.Height ? true : false);

此方法不会导致异常，但应该注意，像这样隐藏滚动条会禁用滚动消息，但如果您只是在文本区域无法滚动时隐藏滚动条，这很好。

【讨论】：