UWP App Data存储和获取

这篇博客介绍如何在UWP开发时，如何存储App Data和获取。

App Data是指用户的一些设定，偏好等。例如，App的主题，是否接收推送，离线接收消息等。需要区分下App Data和User Data，一般情况下User Data是一些文档，文件，数据库记录。

App Data的类型有Settings和Files两类。

Settings中支持的数据类型下面几种，

UInt8, Int16, UInt16, Int32, UInt32, Int64, UInt64, Single, Double
Boolean
Char16, String
DateTime, TimeSpan
GUID, Point, Size, Rect
ApplicationDataCompositeValue

App Data可以存储在LocalSetting，RoamingSetting中，两者的区别是LocalSetting存储在本地，RoamingSetting是存储在漫游文件夹中。另外存储在RoamingSetting中的内容可以在同一个App的多个设备上共享数据。注意，RoamingSetting的存储空间是有限的，尽量存储一些必要的信息。

LocalSetting示例：

Windows.Storage.ApplicationDataContainer localSettings =
    Windows.Storage.ApplicationData.Current.LocalSettings;// Create a setting
localSettings.Values["ExampleSetting"] = "Hello Windows";

// Retrieve the setting
object value = localSettings.Values["ExampleSetting"];

// Composite setting
Windows.Storage.ApplicationDataCompositeValue composite =
    new Windows.Storage.ApplicationDataCompositeValue();

composite["intVal"] = 1;
composite["strVal"] = "string";

localSettings.Values["exampleCompositeSetting"] = composite;

// Retrieve composite setting
Windows.Storage.ApplicationDataCompositeValue compositeValue =
    (Windows.Storage.ApplicationDataCompositeValue)localSettings.Values["exampleCompositeSetting"];

if(compositeValue != null)
{
    int intVal = (int)compositeValue["intVal"];

    string strVal = (string)compositeValue["strVal"];
}

RoamingSetting

Windows.Storage.ApplicationDataContainer roamingSettings =
    Windows.Storage.ApplicationData.Current.RoamingSettings;// Create roaming settings

roamingSettings.Values["exampleSetting"] = "Hello World";

roamingSettings.Values["HighPriority"] = "65";

// Composite setting
Windows.Storage.ApplicationDataCompositeValue composite =
    new Windows.Storage.ApplicationDataCompositeValue();

composite["intVal"] = 1;
composite["strVal"] = "string";

roamingSettings.Values["exampleCompositeSetting"] = composite;

// Retrive composite setting
Windows.Storage.ApplicationDataCompositeValue compositeValue =
    (Windows.Storage.ApplicationDataCompositeValue)roamingSettings.Values["exampleCompositeSetting"];

if(compositeValue != null)
{
    int intValue = (int)compositeValue["intVal"];

    string strValue = (string)compositeValue["strVal"];
}

可以看到，Setting中的所有数据都是以key-value形式存储的。

感谢您的阅读。