C# Clipboard.GetText返回null（空字符串）

我的剪贴板中填充了文本，但当我运行

string clipboardData = Clipboard.GetText(System.Windows.Forms.TextDataFormat.Text);

我得到一个空字符串。我曾尝试过各种形式的通话，包括：

string clipboardData = Clipboard.GetText();
string clipboardData = Clipboard.GetText(System.Windows.Forms.TextDataFormat.UnicodeText);

但结果是一样的

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我是否遗漏了一些明显的内容？

您只能从STA线程访问剪贴板。Rick Brewster在Paint.NET中对常规的Edit->Paste命令进行重构后遇到了这种情况

代码：

代码来自瑞克

---

更新：在

委托

之后添加

（）

，以修复不明确的方法错误。

由于某些原因，BoltBait的代码不能正常工作（即使在staThread.Join（）之后，idat仍然为null）。我只是在staThread委托内部执行了Clipboard.GetText（），而不是Clipboard.GetDataObject（），这很好

---

尽管如此，还是要感谢您——您的代码片段让我获得了99%的成功：）

我已经编写了这个类，它可以工作，并且做同样的事情，只需添加您需要的方法即可轻松改进

    Private Class ClipboardAsync

    Private _GetText As String
    Private Sub _thGetText(ByVal format As Object)
        Try
            If format Is Nothing Then
                _GetText = Clipboard.GetText()
            Else
                _GetText = Clipboard.GetText(DirectCast(format, TextDataFormat))
            End If

        Catch ex As Exception
            _GetText = String.Empty
        End Try
    End Sub
    Public Function GetText() As String
        Dim instance As New ClipboardAsync
        Dim staThread As New Thread(AddressOf instance._thGetText)
        staThread.SetApartmentState(ApartmentState.STA)
        staThread.Start()
        staThread.Join()
        Return instance._GetText
    End Function
    Public Function GetText(ByVal format As TextDataFormat) As String
        Dim instance As New ClipboardAsync
        Dim staThread As New Thread(AddressOf instance._thGetText)
        staThread.SetApartmentState(ApartmentState.STA)
        staThread.Start(format)
        staThread.Join()
        Return instance._GetText
    End Function

    Private _ContainsText As Boolean
    Private Sub _thContainsText(ByVal format As Object)
        Try
            If format Is Nothing Then
                _ContainsText = Clipboard.ContainsText()
            Else
                _ContainsText = Clipboard.ContainsText(DirectCast(format, TextDataFormat))
            End If
        Catch ex As Exception
            _ContainsText = False
        End Try
    End Sub
    Public Function ContainsText() As Boolean
        Dim instance As New ClipboardAsync
        Dim staThread As New Thread(AddressOf instance._thContainsFileDropList)
        staThread.SetApartmentState(ApartmentState.STA)
        staThread.Start()
        staThread.Join()
        Return instance._ContainsText
    End Function
    Public Function ContainsText(ByVal format As Object) As Boolean
        Dim instance As New ClipboardAsync
        Dim staThread As New Thread(AddressOf instance._thContainsFileDropList)
        staThread.SetApartmentState(ApartmentState.STA)
        staThread.Start(format)
        staThread.Join()
        Return instance._ContainsText
    End Function

    Private _ContainsFileDropList As Boolean
    Private Sub _thContainsFileDropList(ByVal format As Object)
        Try
            _ContainsFileDropList = Clipboard.ContainsFileDropList
        Catch ex As Exception
            _ContainsFileDropList = False
        End Try
    End Sub
    Public Function ContainsFileDropList() As Boolean
        Dim instance As New ClipboardAsync
        Dim staThread As New Thread(AddressOf instance._thContainsFileDropList)
        staThread.SetApartmentState(ApartmentState.STA)
        staThread.Start()
        staThread.Join()
        Return instance._ContainsFileDropList
    End Function

    Private _GetFileDropList As Specialized.StringCollection
    Private Sub _thGetFileDropList()
        Try
            _GetFileDropList = Clipboard.GetFileDropList
        Catch ex As Exception
            _GetFileDropList = Nothing
        End Try
    End Sub
    Public Function GetFileDropList() As Specialized.StringCollection
        Dim instance As New ClipboardAsync
        Dim staThread As New Thread(AddressOf instance._thGetFileDropList)
        staThread.SetApartmentState(ApartmentState.STA)
        staThread.Start()
        staThread.Join()
        Return instance._GetFileDropList
    End Function
End Class

以下是CSharp版本：

private class ClipboardAsync
{

private string _GetText;
private void _thGetText(object format)
{
    try {
        if (format == null) {
            _GetText = Clipboard.GetText();
        }
        else {
            _GetText = Clipboard.GetText((TextDataFormat)format);
            
        }
    }
    catch (Exception ex) {
        //Throw ex 
        _GetText = string.Empty;
    }
}
public string GetText()
{
    ClipboardAsync instance = new ClipboardAsync();
    Thread staThread = new Thread(instance._thGetText);
    staThread.SetApartmentState(ApartmentState.STA);
    staThread.Start();
    staThread.Join();
    return instance._GetText;
}
public string GetText(TextDataFormat format)
{
    ClipboardAsync instance = new ClipboardAsync();
    Thread staThread = new Thread(instance._thGetText);
    staThread.SetApartmentState(ApartmentState.STA);
    staThread.Start(format);
    staThread.Join();
    return instance._GetText;
}

private bool _ContainsText;
private void _thContainsText(object format)
{
    try {
        if (format == null) {
            _ContainsText = Clipboard.ContainsText();
        }
        else {
            _ContainsText = Clipboard.ContainsText((TextDataFormat)format);
        }
    }
    catch (Exception ex) {
        //Throw ex 
        _ContainsText = false;
    }
}
public bool ContainsText()
{
    ClipboardAsync instance = new ClipboardAsync();
    Thread staThread = new Thread(instance._thContainsFileDropList);
    staThread.SetApartmentState(ApartmentState.STA);
    staThread.Start();
    staThread.Join();
    return instance._ContainsText;
}
public bool ContainsText(object format)
{
    ClipboardAsync instance = new ClipboardAsync();
    Thread staThread = new Thread(instance._thContainsFileDropList);
    staThread.SetApartmentState(ApartmentState.STA);
    staThread.Start(format);
    staThread.Join();
    return instance._ContainsText;
}

private bool _ContainsFileDropList;
private void _thContainsFileDropList(object format)
{
    try {
        _ContainsFileDropList = Clipboard.ContainsFileDropList();
    }
    catch (Exception ex) {
        //Throw ex 
        _ContainsFileDropList = false;
    }
}
public bool ContainsFileDropList()
{
    ClipboardAsync instance = new ClipboardAsync();
    Thread staThread = new Thread(instance._thContainsFileDropList);
    staThread.SetApartmentState(ApartmentState.STA);
    staThread.Start();
    staThread.Join();
    return instance._ContainsFileDropList;
}

private Specialized.StringCollection _GetFileDropList;
private void _thGetFileDropList()
{
    try {
        _GetFileDropList = Clipboard.GetFileDropList();
    }
    catch (Exception ex) {
        //Throw ex 
        _GetFileDropList = null;
    }
}
public Specialized.StringCollection GetFileDropList()
{
    ClipboardAsync instance = new ClipboardAsync();
    Thread staThread = new Thread(instance._thGetFileDropList);
    staThread.SetApartmentState(ApartmentState.STA);
    staThread.Start();
    staThread.Join();
    return instance._GetFileDropList;
}
}

您可以简单地将其用于： Vb.net：

Csharp：

ClipboardAsync Clipboard2 = new ClipboardAsync();
MessageBox.Show (Clipboard2.ContainsText());

---

老实说，我不知道STA线程是什么，但在简单的项目中，在

Main

方法之前添加

[STAThread]

可能会解决问题：

[STAThread]
static void Main(string[] args)
{ (...)

它对我有效，因此我不怀疑该方法；）

---

---

有关

[STAThread]

装饰器的更多信息，请参阅博客文章。

这是一个线程问题。我们必须获得正确的线程并通过委托执行

我正在通过每500毫秒一次的计时器更新我的属性。以下是代码：

    public delegate void ClipboarDelegate();

    ClipboarDelegate clipboardDelegate = null;

    void clipboardTimer_Elapsed(object sender, ElapsedEventArgs e)
    {
        if (clipboardDelegate == null)
            clipboardDelegate = ClipboarDelegateMethod;

        //Here we get the right thread, most probably the application thread
        Application.Current.Dispatcher.BeginInvoke(clipboardDelegate);
    }

    public void ClipboarDelegateMethod()
    {
        try
        {
            if (Clipboard.ContainsData(DataFormats.Text))
            {
                //It's important to lock this section
                lock (ClipboardString)
                {
                    ClipboardString = Clipboard.GetData(DataFormats.Text) as string;
                }
            }
        }
        catch
        { }
    }

此外，我还使用ClipboardString创建了一个适当的DependencyProperty：

    public static readonly DependencyProperty ClipboardStringDP =
        DependencyProperty.Register("ClipboardString",
                                    typeof(string),
                                    typeof(MainWindow),
                                    new UIPropertyMetadata(string.Empty));

    public string ClipboardString
    {
        get { return (string)this.GetValue(ClipboardStringDP); }
        set { this.SetValue(ClipboardStringDP, value); }
    }

通过这种方式，它可以绑定到XAML中的我的文本框，假设我的控件或窗口

x:Name=“\u This”

：

---

BoltBait的代码不适用于IDataObject，因为数据对象在线程外丢失信息。如果IDataObject仅在线程内部使用，则一切正常，如下所示：

IDataObject idat = null;
Exception threadEx = null;
String text = "";
Thread staThread = new Thread(
    delegate ()
    {
        try
        {
            idat = Clipboard.GetDataObject();
            text = idat.GetData(DataFormats.Text)
        }

        catch (Exception ex) 
        {
            threadEx = ex;            
        }
    });
staThread.SetApartmentState(ApartmentState.STA);
staThread.Start();
staThread.Join();
// here you can use text, which contains data from clipboard

---

如何将数据放入剪贴板？剪贴板上的数据是否为“文本”，而不是图形、音频或其他？空字符串与空字符串非常不同。我不知道为什么“空”是你问题的一部分。它只会增加混乱和错误信息。嗨，Jonathan-我看到了完全相同的事情，也做了同样的事情。我不确定其他框架，但在.net 4.0中，委托需要在它后面有（），否则你会得到一个不明确的方法错误。我们应该添加一些锁定吗？回答很好，虽然在我的例子中，我只是在WinForms中删除了Main上的[StatThread]属性，所以我不得不将其放回原处。您好，我发现有时候在StatThread.Join（）返回后剪贴板内容无法立即使用。e、 如果我尝试使用idat，我会得到一个旧值或null等；然而，如果我在尝试访问VARABLE之前加上1秒睡眠，它就会工作。为什么会出现这种情况，有什么建议吗？我可以提出一个新问题吗？如果答案是我们在访问变量之前需要一个睡眠来进行可靠的读取，我认为这在这里是相关的。哦，上帝，这帮了我很多！！非常感谢！完美的快速控制台应用程序。工作就像一个魅力！干杯这是否意味着对原始问题的另一个回答？如果是，那么它提供了什么新功能？

    public static readonly DependencyProperty ClipboardStringDP =
        DependencyProperty.Register("ClipboardString",
                                    typeof(string),
                                    typeof(MainWindow),
                                    new UIPropertyMetadata(string.Empty));

    public string ClipboardString
    {
        get { return (string)this.GetValue(ClipboardStringDP); }
        set { this.SetValue(ClipboardStringDP, value); }
    }

<TextBox Name="ClipBoardTextBox"
         DataContext="{Binding ElementName=_this}"
         Text="{Binding Path=ClipboardString, Mode=OneWay}"/>

IDataObject idat = null;
Exception threadEx = null;
String text = "";
Thread staThread = new Thread(
    delegate ()
    {
        try
        {
            idat = Clipboard.GetDataObject();
            text = idat.GetData(DataFormats.Text)
        }

        catch (Exception ex) 
        {
            threadEx = ex;            
        }
    });
staThread.SetApartmentState(ApartmentState.STA);
staThread.Start();
staThread.Join();
// here you can use text, which contains data from clipboard