读取和写入 XML 文件的异步方法

Question

我在 android/ios 和 windows phone 中使用 DependencyService 在我的 Xamarin.forms 项目中写入和读取 XML 文件。我指的是working with files。

我能够实现示例中给出的功能，但我真正想要的是读取和写入 XML 文件。

我按照通常的 c# 程序来读取和写入 xml 文件，但由于方法是异步的而出现错误。

我从来没有使用过异步等待方法，所以不知道如何去做。

这是我尝试过的：

public async Task SaveTextAsync(string filename, string text)
{
    ApplicationData data = new ApplicationData();
    ApplicationVersion version = new ApplicationVersion();
    version.SoftwareVersion = "test";
    data.ApplicationVersion = version;

    XmlSerializer writer =
        new XmlSerializer(typeof(ApplicationData));
    System.IO.FileStream file = System.IO.File.Create(path);

    writer.Serialize(file, data);
    file.Close();
}

public async Task<string> LoadTextAsync(string filename)
{
    var path = CreatePathToFile(filename);
    ApplicationData cars = null;
    XmlSerializer serializer = new XmlSerializer(typeof(ApplicationData));
    StreamReader reader = new StreamReader(path);
    cars = (ApplicationData)serializer.Deserialize(reader);
    reader.Close();
}
string CreatePathToFile(string filename)
{
    var docsPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
    return Path.Combine(docsPath, filename);
}

编辑

工作读写txt文件代码在这里：

public async Task SaveTextAsync (string filename, string text)
{
    var path = CreatePathToFile (filename);
    using (StreamWriter sw = File.CreateText (path))
        await sw.WriteAsync(text);
}

public async Task<string> LoadTextAsync (string filename)
{
    var path = CreatePathToFile (filename);
    using (StreamReader sr = File.OpenText(path))
        return await sr.ReadToEndAsync();
}

Answer 1

我设法让它工作。这是我的代码：

public async Task SaveTextAsync(string filename)
{
    var path = CreatePathToFile(filename);
    ApplicationData data = new ApplicationData();
    ApplicationVersion version = new ApplicationVersion();
    version.SoftwareVersion = "test version";
    data.ApplicationVersion = version;
    XmlSerializer writer =
        new XmlSerializer(typeof(ApplicationData));
    System.IO.FileStream file = System.IO.File.Create(path);
    writer.Serialize(file, data);
    file.Close();

}

public async Task<ApplicationData> LoadTextAsync(string filename)
{
    var path = CreatePathToFile(filename);

    ApplicationData records = null;
    await Task.Run(() =>
    {
        // Create an instance of the XmlSerializer specifying type and namespace.
        XmlSerializer serializer = new XmlSerializer(typeof(ApplicationData));

        // A FileStream is needed to read the XML document.
        FileStream fs = new FileStream(path, FileMode.Open);
        XmlReader reader = XmlReader.Create(fs);

        // Use the Deserialize method to restore the object's state.
        records = (ApplicationData)serializer.Deserialize(reader);
        fs.Close();
    });
    return records;
}