从 SQL DB 检索时 Excel 文件损坏

Question

我正在使用将 Excel 文件（以及其他文件类型，例如 PDF）存储为二进制数据的 SQL DB。我使用以下代码将这些文件提取到文件系统上。

问题： PDF 文件输出得很好。但对于 Excel，文件已创建，当我尝试打开它们时，它们崩溃或只是给我垃圾文本。

我正在使用前一个编写此应用程序的人提供的代码来检索文件。这段代码使用了我不完全理解的 OpenMcdf，因为我找不到有用的在线文档。

//execution starts here
public override void SaveToDisk()
{

    byte[] keys = { (byte)0xd0, (byte)0xcf };


    //Searches through m_RawOleObject for combination of 'keys'
    int offset = Utils.SearchBytes(m_RawOleObject, keys); //returns '60' in case of Excel and '66' in case of Pdf

    //m_RawOleOjbect contains the data from the sqlDataReader (the binary data from the column.)
    m_RawOleObject = strip(m_RawOleObject, offset);

    MemoryStream ms = new MemoryStream(m_RawOleObject);
    CompoundFile cf = new CompoundFile(ms);
    GetStorageByName(cf.RootStorage, m_StorageName);

    if (Storage != null)
    {
        if (Storage is CFStream)
        {
            m_RawOleObject = (Storage as CFStream).GetData();
        }
        m_filename = System.IO.Path.Combine(STOREPATH, Utils.CombineFilenameWithExtension(Filename, m_extension));

        WriteToFile(m_filename, m_RawOleObject);
    }

}

protected void WriteToFile(string fn, byte[] obj)
{
    fn = GetNextAvailableFilename(fn, 0);
    FileStream fs = new FileStream(fn, FileMode.Create);
    BinaryWriter writer = new BinaryWriter(fs);
    writer.Write(obj);
    writer.Close();
    fs.Close();
    fs.Dispose();
}


protected void GetStorageByName(CFStorage cfs, string name)
{
    VisitedEntryAction va = delegate(CFItem target)
    {
        if (target is CFStorage)
        {
            GetStorageByName((CFStorage)target, name);
        }
        else
        {
            if (target.Name == name)
                Storage = target;
        }
    };

    //Visit NON-recursively (first level only)
    cfs.VisitEntries(va, false);
}

你知道这里发生了什么吗？为什么excel被破坏了？尽管搜索了几个小时，我在网上还是找不到很多东西！

任何想法、建议或解决方案将不胜感激。

谢谢

Answer 1

按如下方式更改 SaveToDisk 逻辑：

public override void SaveToDisk()
{
    byte[] keys = { (byte)0xd0, (byte)0xcf, (byte)0x11, (byte)0xe0, (byte)0xa1, (byte)0xb1, (byte)0x1a, (byte)0xe1 };
    int offset = Utils.SearchBytes(m_RawOleObject, keys);
    using (MemoryStream ms = new MemoryStream(strip(m_RawOleObject, offset)))
    {
        CompoundFile cf = new CompoundFile(ms, UpdateMode.ReadOnly, true, true);
        m_filename = GetNextAvailableFilename(System.IO.Path.Combine(STOREPATH, Utils.CombineFilenameWithExtension(Filename, m_extension)), 0);
        using (var fs = new FileStream(m_filename, FileMode.Create))
        {
            cf.Save(fs);
            cf.Close();
        }
    }

    //Workbook would be saved as hidden in previous step
    Microsoft.Office.Interop.Excel.Application xlApp = null;
    Microsoft.Office.Interop.Excel.Workbook xlWb = null;
    try
    {
        xlApp = new Microsoft.Office.Interop.Excel.Application();
        xlWb = xlApp.Workbooks.Open(m_filename);
        xlWb.CheckCompatibility = false;

        foreach (Window wn in xlApp.Windows)
        {
            wn.Visible = true;
        }
        xlWb.Save();
        xlWb.Close();
    }
    catch (Exception e)
    {
        //TODO: Log error and continue
    }
    finally
    {
        if (xlWb != null)
            Marshal.ReleaseComObject(xlWb);
        if (xlApp != null)
            Marshal.ReleaseComObject(xlApp);
        xlApp = null;
    }
}