[英]C# Serialization to file, overwrite if exists
我有以下方法(如下所示),因為您可以看到它將對象序列化為XML文件。 我遇到的主要問題是我想讓函數覆蓋文件(如果存在)。 我知道如果它確實存在,我可以先刪除該文件,但這也意味着我可能會在我的應用程序中引入一些錯誤。 所以我想要一個全有或全無,覆蓋方法......
這是關於如何實現這一功能的任何想法?
/// <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);
}
}
使用帶有Stream
而不是字符串的XmlWriter.Create
的重載版本,並使用File.Create
創建/覆蓋該文件:
using (var w = XmlWriter.Create(File.Create(fileName), settings))
...
-
FileStream stream = File.Open(filename, FileMode.Create, FileAccess.Write, FileShare.None);
using (XmlWriter writer = XmlWriter.Create(stream))
{
...
}
FileStream和XMLWriter應放在using塊中
using (FileStream fs = File.Create(filename))
using (var w = XmlWriter.Create(fs, settings))
{
// your code
}
我相信使用下面的代碼將無法釋放文件流。 因此,如果您在一個會話中運行代碼兩次,它將失敗
using (var w = XmlWriter.Create(File.Create(filename), settings))
XmlWriter.Create(filename,settings)將覆蓋該文件。 如果你對此有例外,那么還有其他事情要發生。 另請參閱: 文件已存在時創建XmlWriter時出錯
備份目標文件(如果存在),如果發生錯誤,則寫回文件。
您可以將新XML文件保存在臨時文件中:
./directory/myNewObject.xml.temp
然后使用File.MoveTo在myNewObject.xml中重命名myNewObject.xml.temp
你可以做以下事情。 將您的xml寫入StringBuilder(),然后將stringBuilder的內容寫入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());
}
注意FileMode,如果使用FileMode.OpenOrCreate,它將不會刪除舊文件內容,如果新內容小於舊內容,則xml將損壞。 確保使用FileMode.Create。
這是一個擴展,它首先寫入本地.tmp文件,如果成功,它將替換所需的文件名。 我選擇使用File.Copy來允許.NET。
如果你更偏執,你可以在網上找到如何為文件交換創建NTFS事務的例子,盡管它需要外部調用。 例如https://improve.dk/utilizing-transactional-ntfs-through-dotnet/
根據它失敗的位置(階段),它將嘗試清理.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;
}
}
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.