Windows 8学习笔记(四)--Storage数据存储
AppData在Metro App中的存储主要由两种形式，一种是键值对的形式，还有一种是StorageFile文件的存储形式。
其中键值对形式的存储又分几种：ApplicationDataCompositeValue复合值存储、ApplicationDataContainer容器数据存储、ApplicationDataContainerSettings普通的容器数据存储。
注意这种键值对的存储值只能以字符形式存储，若要存储某对象，需转成XML或json等其它字符数据。
ApplicationDataCompositeValue的用法
支持复合值的存储
Windows.Storage.ApplicationDataContainer localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;
// Create a composite setting Windows.Storage.ApplicationDataCompositeValue composite = new Windows.Storage.ApplicationDataCompositeValue();
composite["intVal"] = 1;
composite["strVal"] = "string";
localSettings.Values["exampleCompositeSetting"] = composite;
// Read data from a composite settingWindows.Storage.ApplicationDataCompositeValue composite = (Windows.Storage.ApplicationDataCompositeValue)localSettings.Values["exampleCompositeSetting"];
// Delete a composite setting
localSettings.Values.Remove("exampleCompositeSetting");
ApplicationDataContainer的用法
支持创建、删除、枚举、数据容器层次的贯穿
Windows.Storage.ApplicationDataContainer localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;
// Create a setting in a container
Windows.Storage.ApplicationDataContainer container =
localSettings.CreateContainer("exampleContainer", Windows.Storage.ApplicationDataCreateDisposition.Always);
if (localSettings.Containers.ContainsKey("exampleContainer"))
{
localSettings.Containers["exampleContainer"].Values["exampleSetting"] = "Hello Windows";
}
// Read data from a setting in a container
bool hasContainer = localSettings.Containers.ContainsKey("exampleContainer");
bool hasSetting = false;
if (hasContainer)
{
hasSetting = localSettings.Containers["exampleContainer"].Values.ContainsKey("exampleSetting");
}
// Delete a container
localSettings.DeleteContainer("exampleContainer");
ApplicationDataContainerSettings的用法
最简单的键值对存储
var localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;
// Create a simple setting
localSettings.Values["exampleSetting"] = "Hello Windows 8";
if (localSettings.Values.ContainsKey("exampleSetting"))
{
// Read data from a simple setting
Object value = localSettings.Values["exampleSetting"];
}
localSettings.Values.Remove("exampleSetting");
StorageFile的存储，以文件的形式进行存储
存入数据
static async public Task SaveAsync
(T data,string fileName)
{
// Get the output stream for the SessionState file.
StorageFile file = await ApplicationData.Current.LocalFolder.CreateFileAsync(fileName, CreationCollisionOption.ReplaceExisting);
IRandomAccessStream raStream = await file.OpenAsync(FileAccessMode.ReadWrite);
using (IOutputStream outStream = raStream.GetOutputStreamAt(0))
{
// Serialize the Session State.
DataContractSerializer serializer = new DataContractSerializer(typeof(T));
serializer.WriteObject(outStream.AsStreamForWrite(), data);
await outStream.FlushAsync();
}
}
取文件数据
static async public Task
RestoreAsync
(string filename) { // Get the input stream for the SessionState file. T sessionState_ = default(T); try { StorageFile file = await ApplicationData.Current.LocalFolder.GetFileAsync(filename); if (file == null) return sessionState_; IInputStream inStream = await file.OpenSequentialReadAsync(); // Deserialize the Session State. DataContractSerializer serializer = new DataContractSerializer(typeof(T)); sessionState_= (T)serializer.ReadObject(inStream.AsStreamForRead()); } catch (Exception) { // Restoring state is best-effort. If it fails, the app will just come up with a new session. } return sessionState_; }
以上就是Metro Style App中数据存储的几种方式，怎么样，跟Windows Phone7中还是有些差别的吧。。。
顺便整理一下xml/json格式数据的序列与反序列化的通用方法
JSON数据的序列与反序列
public static T DataContractJsonDeSerializer
(string jsonString)
{
var ds = new DataContractJsonSerializer(typeof(T));
var ms = new MemoryStream(Encoding.UTF8.GetBytes(jsonString));
T obj = (T)ds.ReadObject(ms);
ms.Dispose();
return obj;
}
public static string ToJsonData(object item)
{
DataContractJsonSerializer serializer = new DataContractJsonSerializer(item.GetType());
string result = String.Empty;
using (MemoryStream ms = new MemoryStream())
{
serializer.WriteObject(ms, item);
ms.Position = 0;
using (StreamReader reader = new StreamReader(ms))
{
result = reader.ReadToEnd();
}
}
return result;
}
XML数据的序列与反序列
////// 需要序列化XML数据对象 /// ///public static string XMLSerialize(object objectToSerialize) { string result = ""; using (MemoryStream ms = new MemoryStream()) { DataContractSerializer serializer = new DataContractSerializer(objectToSerialize.GetType()); serializer.WriteObject(ms, objectToSerialize); ms.Position = 0; using (StreamReader reader = new StreamReader(ms)) { result = reader.ReadToEnd(); } } return result; } /// /// XML数据反序列化 /// ///反序列化对象 ///public static T XMLDeserialize (string xmlstr) { byte[] newBuffer = System.Text.Encoding.UTF8.GetBytes(xmlstr); if (newBuffer.Length == 0) { return default(T); } using (MemoryStream ms = new MemoryStream(newBuffer)) { DataContractSerializer serializer = new DataContractSerializer(typeof(T)); return (T)serializer.ReadObject(ms); } }