在 Windows 8 应用程序中保存 List<Object> 的最佳方法是什么

Question

我有一个List<class> 的数据。我想保存它并在我的应用程序每次启动和退出时分别检索它。 Windows 8 中 IsolatedStorage (WP7) 的等效项是什么。如何保存这些设置？

Answer 1

在 Windows 8 中，您必须为您的应用使用 LocalFolder，您可以使用以下方式访问：

StorageFolder folder = ApplicationData.Current.LocalFolder;

然后使用以下方法引用保存在那里的文件：

var fileToGet = await folder.GetFileAsync("nameOfFile.fileType");

我目前在我正在处理的项目中处于类似情况，我想将自定义对象列表存储到我的 Apps LocalFolder 并稍后重新加载。

我的解决方案是将列表序列化为 XML 字符串，并将其存储在 App 文件夹中。你应该能够适应我的方法：

static public string SerializeListToXml(List<CustomObject> List)
    {
        try
        {
            XmlSerializer xmlIzer = new XmlSerializer(typeof(List<CustomObject>));
            var writer = new StringWriter();
            xmlIzer.Serialize(writer, List);
            System.Diagnostics.Debug.WriteLine(writer.ToString());
            return writer.ToString();
        }

        catch (Exception exc)
        {
            System.Diagnostics.Debug.WriteLine(exc);
            return String.Empty;
        }

现在您有了字符串，您可以将其保存为文本文件并将其放入 LocalStorage：

//assuming you already have a list with data called myList
await Windows.Storage.FileIO.WriteTextAsync("xmlFile.txt", SerializeListToXml(myList));

现在当你再次加载你的应用程序时，你可以使用上面提到的加载方法从 LocalStorage 中获取 xmlFile，然后将其反序列化以获取你的 List。

string listAsXml = await Windows.Storage.FileIO.ReadTextAsync(xmlFile.txt);
List<CustomObject> deserializedList = DeserializeXmlToList(listAsXml);

再次，根据您的需要调整它：

public static List<CustomObject> DeserializeXmlToList(string listAsXml)
    {
        try
        {
            XmlSerializer xmlIzer = new XmlSerializer(typeof(List<CustomObject>));
            XmlReader xmlRead = XmlReader.Create(listAsXml);
            List<CustomObject> myList = new List<CustomObject>();
            myList = (xmlIzer.Deserialize(xmlRead)) as List<CustomObject>;
            return myList;
        }

        catch (Exception exc)
        {
            System.Diagnostics.Debug.WriteLine(exc);
            List<CustomObject> emptyList = new List<CustomObject>();
            return emptyList;
        }
    }

Answer 2

你可以使用这个类来存储和加载设置：

public static class ApplicationSettings
{
    public static void SetSetting<T>(string key, T value, bool roaming = true)
    {
        var settings = roaming ? ApplicationData.Current.RoamingSettings : ApplicationData.Current.LocalSettings;
        settings.Values[key] = value;
    }

    public static T GetSetting<T>(string key, bool roaming = true)
    {
        return GetSetting(key, default(T), roaming);
    }

    public static T GetSetting<T>(string key, T defaultValue, bool roaming = true)
    {
        var settings = roaming ? ApplicationData.Current.RoamingSettings : ApplicationData.Current.LocalSettings;
        return settings.Values.ContainsKey(key) &&
               settings.Values[key] is T ?
               (T)settings.Values[key] : defaultValue;
    }

    public static bool HasSetting<T>(string key, bool roaming = true)
    {
        var settings = roaming ? ApplicationData.Current.RoamingSettings : ApplicationData.Current.LocalSettings;
        return settings.Values.ContainsKey(key) && settings.Values[key] is T;
    }

    public static bool RemoveSetting(string key, bool roaming = true)
    {
        var settings = roaming ? ApplicationData.Current.RoamingSettings : ApplicationData.Current.LocalSettings;
        if (settings.Values.ContainsKey(key))
            return settings.Values.Remove(key);
        return false;
    }
}

但您只能保存和加载原始类型（bool、int、string 等）。这就是为什么您必须将您的列表序列化为 XML 或其他可以存储在字符串中的格式。要在 XML 中序列化和反序列化对象，您可以使用以下方法：

public static string Serialize(object obj)
{
    using (var sw = new StringWriter()) 
    {
        var serializer = new XmlSerializer(obj.GetType());
        serializer.Serialize(sw, obj);
        return sw.ToString();
    }
}

public static T Deserialize<T>(string xml)
{
    using (var sw = new StringReader(xml))
    {
        var serializer = new XmlSerializer(typeof(T));
        return (T)serializer.Deserialize(sw);
    }
}

另见Is there a way to store instances of own classes in the ApplicationSettings of a Windows Store app?