Question

我有以下方法（如下所示），因为您可以看到它将对象序列化为XML文件。我遇到的主要问题是我想让函数覆盖文件（如果存在）。我知道如果它确实存在，我可以先删除该文件，但这也意味着我可能会在我的应用程序中引入一些错误。所以我想要一个全有或全无的覆盖方法...

这是函数，关于如何实现这一点的任何想法？

/// <summary>
    /// Serializes an object to an xml file.
    /// </summary>
    /// <param name="obj">
    /// The object to serialize.
    /// </param>
    /// <param name="type">
    /// The class type of the object being passed.
    /// </param>
    /// <param name="fileName">
    /// The filename where the object should be saved to.
    /// </param>
    /// <param name="xsltPath">
    /// Pass a null if not required.
    /// </param>
    public static void SerializeToXmlFile(object obj, Type type, string fileName, string xsltPath )
    {
        var ns = new XmlSerializerNamespaces();
        ns.Add(String.Empty, String.Empty);
        var serializer = new XmlSerializer(type);

        var settings = new XmlWriterSettings {Indent = true, IndentChars = "\t"};


        using (var w = XmlWriter.Create(fileName,settings))
        {

            if (!String.IsNullOrEmpty(xsltPath))
            {
                w.WriteProcessingInstruction("xml-stylesheet", "type=\"text/xsl\" href=\"" + xsltPath + "\"");

            }
            serializer.Serialize(w, obj, ns);
        }
    }

Answer 1

使用XmlWriter.Create的重载版本，其中包含Stream而不是字符串，并使用File.Create创建/覆盖该文件：

using (var w = XmlWriter.Create(File.Create(fileName), settings))
...

Answer 2

使用File.Open（）使用FileMode.Create，FileAccess.Write和FileShare.None打开文件。
将从File.Open（）返回的流传递给XmlWriter.Create（）。

-

FileStream stream = File.Open(filename, FileMode.Create, FileAccess.Write, FileShare.None);
using (XmlWriter writer = XmlWriter.Create(stream))
{
    ...
}

Answer 3

FileStream和XMLWriter应放在using块

中

using (FileStream fs = File.Create(filename))
using (var w = XmlWriter.Create(fs, settings))
{
    // your code
}

我相信使用下面的代码将无法释放文件流。因此，如果您在一个会话中运行代码两次，它将失败

using (var w = XmlWriter.Create(File.Create(filename), settings))

Answer 4

XmlWriter.Create（filename，settings）将覆盖该文件。如果你对此有例外，那么还有其他事情要发生。另见：Error creating an XmlWriter when file already exists

Answer 5

备份目标文件（如果存在），如果发生错误，请写回文件。

Answer 6

您可以将新的XML文件保存在临时文件中：

./目录/ myNewObject.xml.temp

然后使用File.MoveTo在myNewObject.xml中重命名myNewObject.xml.temp

Answer 7

您可以执行以下操作。将xml写入StringBuilder（），然后将stringBuilder的内容写入file。

    public static void SerializeToXmlFile(object obj, Type type, string fileName, string xsltPath) {
        var ns = new XmlSerializerNamespaces();
        ns.Add(String.Empty, String.Empty);
        var serializer = new XmlSerializer(type);

        var settings = new XmlWriterSettings { Indent = true, IndentChars = "\t" };

        StringBuilder sb = new StringBuilder();
        using (var w = XmlWriter.Create(sb, settings)) {

            if (!String.IsNullOrEmpty(xsltPath)) {
                w.WriteProcessingInstruction("xml-stylesheet", "type=\"text/xsl\" href=\"" + xsltPath + "\"");

            }
            serializer.Serialize(w, obj, ns);
        }

        File.WriteAllText(fileName, sb.ToString());
    }

Answer 8

请注意FileMode，如果使用FileMode.OpenOrCreate，它将不会删除旧文件内容，如果新内容较小，则xml的旧内容将被破坏。确保使用FileMode.Create。

这是一个扩展名，它将首先写入本地.tmp文件，如果成功，它将替换所需的文件名。我选择使用File.Copy来允许.NET。

如果您更偏执，可以在线找到一些示例，该示例说明如何为文件交换创建NTFS事务，尽管它需要外部调用。例如https://improve.dk/utilizing-transactional-ntfs-through-dotnet/

根据失败的位置（阶段），它将尝试清除.tmp文件。

/// <summary>
/// asynchronous serializing of an object at the path specified by the FileInfo.
/// </summary>
/// <typeparam name="T">Type of the object to serialize</typeparam>
/// <param name="fi">FileInfo to the target path</param>
/// <param name="ObjectToSerialize">object to serialize</param>
/// <param name="fileShare">File sharing mode during write</param>
public static void SerializeXmlFile<T>(this FileInfo fi, T ObjectToSerialize, FileShare fileShare) //where T:IXmlSerializable
{
    XmlSerializer serializer = new XmlSerializer(typeof(T));
    var TargetFile = fi.FullName;
    var fiTemp = new FileInfo(fi.FullName + ".tmp");

    int Stage = 0;
    try
    {
        try
        {
            using (StreamWriter writer = new StreamWriter(fiTemp.Open(FileMode.Create, FileAccess.Write, fileShare)))
            {
                serializer.Serialize(writer, ObjectToSerialize);
            }
        }
        catch (Exception e)
        {
            throw new IOException("Unable to serialize to temp file, Error: " + e.Message, e);
        }
        Stage = 1;
        try
        {
            fiTemp.CopyTo(TargetFile, true);
            Stage = 2;
        }
        catch (Exception e)
        {
            throw new IOException("Unable to serialize to final file, Error replacing from temp: " + e.Message, e);
        }
        try
        {
            fiTemp.Delete();
        } catch (FileNotFoundException) { }
        catch (Exception e)
        {
            throw new IOException("Unable to cleanup temp file, Error: " + e.Message, e);
        }
        Stage = 3;


        fi.Refresh();
    }
    catch (Exception)
    {
        throw;
    }
    finally
    {
        switch (Stage)
        {
            case 1: // temp is written
            case 2: // temp is copied to destination, not yet deleted
                {
                    try
                    {
                        fiTemp.Delete();
                    }
                    catch (FileNotFoundException) { }

                }
                break;
        }
    }
}

C＃Serialization to file，覆盖如果存在

8 个答案: