c# - 将 Gmail 附件拖到 c# winform

Question

我正在尝试让应用程序接受从 Gmail 网页拖入的附件。

但是当我直接从站点拖入附件时，e.Data 似乎也不包含任何数据。

    private void Form1_DragDrop(object sender, DragEventArgs e)
    {
        string[] dataFormats = e.Data.GetFormats();
        Type type = e.Data.GetType();
    }

e.Data 是 DataObject 类型。 FileDrop、FileNameW、FileName 为空 DragContext、DragImageBits、chromium/x-renderer-taint 是 System.IO.MemoryStream

没有一个 Memorystream 对象包含拖入的附件的任何文件数据。 也没有任何下载网址。

编辑。 显然，当拖入图片附件时，数据中包含 URL。 但其他附件不带 URL 但是当我将它拖到桌面时，Windows 资源管理器会以某种方式知道从哪里下载它，因此必须有一种方法来检索此 URL。

编辑2 添加了使用 DataObject 的立即窗口查看的数据

    (e.Data as System.Windows.DataObject).GetFormats(false);
{string[4]}
    [0]: "DragContext"
    [1]: "DragImageBits"
    [2]: "chromium/x-renderer-taint"
    [3]: "FileDrop"
(e.Data as System.Windows.DataObject).GetData("DragContext");
'(e.Data as System.Windows.DataObject).GetData("DragContext")' threw an exception of type 'System.Runtime.InteropServices.COMException'
    Data: {System.Collections.ListDictionaryInternal}
    ErrorCode: -2147221404
    HResult: -2147221404
    HelpLink: null
    InnerException: null
    Message: "Invalid FORMATETC structure (Exception from HRESULT: 0x80040064 (DV_E_FORMATETC))"
    Source: "System"
    StackTrace: "   at System.Runtime.InteropServices.ComTypes.IDataObject.GetData(FORMATETC& format, STGMEDIUM& medium)\r\n   at System.Windows.DataObject.OleConverter.GetDataInner(FORMATETC& formatetc, STGMEDIUM& medium)\r\n   at System.Windows.DataObject.OleConverter.GetDataFromOleHGLOBAL(String format, DVASPECT aspect, Int32 index)\r\n   at System.Windows.DataObject.OleConverter.GetDataFromBoundOleDataObject(String format, DVASPECT aspect, Int32 index)\r\n   at System.Windows.DataObject.OleConverter.GetData(String format, Boolean autoConvert, DVASPECT aspect, Int32 index)\r\n   at System.Windows.DataObject.OleConverter.GetData(String format, Boolean autoConvert)\r\n   at System.Windows.DataObject.GetData(String format, Boolean autoConvert)\r\n   at System.Windows.DataObject.GetData(String format)"
    TargetSite: {Void GetData(System.Runtime.InteropServices.ComTypes.FORMATETC ByRef, System.Runtime.InteropServices.ComTypes.STGMEDIUM ByRef)}
(e.Data as System.Windows.DataObject).GetData("DragImageBits");
{System.IO.MemoryStream}
    CanRead: true
    CanSeek: true
    CanTimeout: false
    CanWrite: true
    Capacity: 87144
    Length: 87144
    Position: 0
    ReadTimeout: '((System.IO.Stream)(e.Data as System.Windows.DataObject).GetData("DragImageBits")).ReadTimeout' threw an exception of type 'System.InvalidOperationException'
    WriteTimeout: '((System.IO.Stream)(e.Data as System.Windows.DataObject).GetData("DragImageBits")).WriteTimeout' threw an exception of type 'System.InvalidOperationException'
(e.Data as System.Windows.DataObject).GetData("chromium/x-renderer-taint");
{System.IO.MemoryStream}
    CanRead: true
    CanSeek: true
    CanTimeout: false
    CanWrite: true
    Capacity: 1
    Length: 1
    Position: 0
    ReadTimeout: '((System.IO.Stream)(e.Data as System.Windows.DataObject).GetData("chromium/x-renderer-taint")).ReadTimeout' threw an exception of type 'System.InvalidOperationException'
    WriteTimeout: '((System.IO.Stream)(e.Data as System.Windows.DataObject).GetData("chromium/x-renderer-taint")).WriteTimeout' threw an exception of type 'System.InvalidOperationException'
(e.Data as System.Windows.DataObject).GetData("FileDrop");
'(e.Data as System.Windows.DataObject).GetData("FileDrop")' threw an exception of type 'System.Runtime.InteropServices.COMException'
    Data: {System.Collections.ListDictionaryInternal}
    ErrorCode: -2147221404
    HResult: -2147221404
    HelpLink: null
    InnerException: null
    Message: "Invalid FORMATETC structure (Exception from HRESULT: 0x80040064 (DV_E_FORMATETC))"
    Source: "System"
    StackTrace: "   at System.Runtime.InteropServices.ComTypes.IDataObject.GetData(FORMATETC& format, STGMEDIUM& medium)\r\n   at System.Windows.DataObject.OleConverter.GetDataInner(FORMATETC& formatetc, STGMEDIUM& medium)\r\n   at System.Windows.DataObject.OleConverter.GetDataFromOleHGLOBAL(String format, DVASPECT aspect, Int32 index)\r\n   at System.Windows.DataObject.OleConverter.GetDataFromBoundOleDataObject(String format, DVASPECT aspect, Int32 index)\r\n   at System.Windows.DataObject.OleConverter.GetData(String format, Boolean autoConvert, DVASPECT aspect, Int32 index)\r\n   at System.Windows.DataObject.OleConverter.GetData(String format, Boolean autoConvert)\r\n   at System.Windows.DataObject.GetData(String format, Boolean autoConvert)\r\n   at System.Windows.DataObject.GetData(String format)"
    TargetSite: {Void GetData(System.Runtime.InteropServices.ComTypes.FORMATETC ByRef, System.Runtime.InteropServices.ComTypes.STGMEDIUM ByRef)}

Answer 1

附件被检测为 FileDrop，数据包含附件的 URL，可以通过执行 GetData(DataFormats.Text) 检索。

这里有一些示例代码供您尝试:

private void Form1_DragDrop(object sender, DragEventArgs e) {
    string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
    if (files == null) {
        string url = (string)e.Data.GetData(DataFormats.Text);
        MessageBox.Show(url);
   }
}

private void Form1_DragEnter(object sender, DragEventArgs e) {
    if (e.Data.GetDataPresent(DataFormats.FileDrop)) {
        e.Effect = DragDropEffects.Copy;
    }
}

请注意，处理 DragEnter 事件并将 e.Effect 设置为 DragDropEffects.Copy 很重要，否则 DragDrop 事件将不会触发，或者不会有您需要的数据。