Quickstart: Roaming app data (XAML)
Learn how to store and retrieve settings and files from the roaming app data store. For info about the roaming app data store and why you'd want to use it, see Roaming app data.
Roadmap: How does this topic relate to others? See:
- Roadmap for Windows Runtime apps using C# or Visual Basic
- Roadmap for Windows Runtime apps using C++
Register to receive notification when roaming data changes
Register for the DataChanged event. This example sets DataChangeHandler as the handler for roaming data changes.
void MainPage::InitHandlers() { Windows::Storage::ApplicationData::Current->DataChanged += ref new TypedEventHandler<Windows::Storage::ApplicationData^, Object^> (this, &MainPage::DataChangeHandler); } void MainPage::DataChangeHandler(Windows::Storage::ApplicationData^ appData, Object^) { // TODO: Refresh your data }
Get the containers for the app's settings and files
Use the ApplicationData.RoamingSettings property to get the settings and the ApplicationData.RoamingFolder property to get the files.
ApplicationDataContainer^ roamingSettings = ApplicationData::Current->RoamingSettings; StorageFolder^ roamingFolder = ApplicationData::Current->RoamingFolder;
Write data to a setting
Use the ApplicationDataContainer.Values property to access the settings in the roamingSettings container we got in the previous section. This example creates a setting named exampleSetting.
// Simple setting auto values = roamingSettings->Values; values->Insert("exampleSetting", dynamic_cast<PropertyValue^>(PropertyValue::CreateString("Hello World")));
An ApplicationDataCompositeValue object contains settings that must be accessed atomically. This example creates a composite setting named exampleCompositeSetting and adds it to the roamingSettings container.
// Composite setting ApplicationDataCompositeValue^ composite = ref new ApplicationDataCompositeValue(); composite->Insert("intVal", dynamic_cast<PropertyValue^>(PropertyValue::CreateInt32(1))); composite->Insert("strVal", dynamic_cast<PropertyValue^>(PropertyValue::CreateString("string"))); auto values = roamingSettings->Values; values->Insert("exampleCompositeSetting", composite);
Call the ApplicationDataContainer.CreateContainer method to create a settings container. This example creates a settings container named exampleContainer and adds a setting named exampleSetting. The Always value from the ApplicationDataCreateDisposition enumeration indicates that the container is created if it doesn't already exist.
// Setting in a container ApplicationDataContainer^ container = roamingSettings->CreateContainer("exampleContainer", ApplicationDataCreateDisposition::Always); if (roamingSettings>Containers->HasKey("exampleContainer")) { auto values = roamingSettings>Containers->Lookup("exampleContainer")->Values; values->Insert("exampleSetting", "Hello World"); }
Read data from a setting
Use the ApplicationDataContainer.Values property to access the exampleSetting setting in the roamingSettings container.
// Simple setting auto values = roamingSettings->Values; String^ value = safe_cast<String^>(roamingSettings->Values->Lookup("exampleSetting"));
Use the ApplicationDataContainer.Values property to access the exampleCompositeSetting setting in the roamingSettings container.
// Composite setting ApplicationDataCompositeValue^ composite = safe_cast<ApplicationDataCompositeValue^>(roamingSettings->Values->Lookup("exampleCompositeSetting")); if (composite == nullptr) { // No data } else { int one = safe_cast<IPropertyValue^>(composite->Lookup("intVal"))->GetInt32(); String^ hello = safe_cast<String^>(composite->Lookup("strVal")); }
Use the ApplicationDataContainer.Values property to access the exampleSetting setting in the exampleContainer container.
// Setting in a container bool hasContainer = roamingSettings->Containers->HasKey("exampleContainer"); bool hasSetting = false; if (hasContainer) { auto values = roamingSettings->Containers->Lookup("exampleContainer")->Values; hasSetting = values->HasKey("exampleSetting"); }
Write data to a file
Use the file APIs, such as Windows.Storage.StorageFolder.CreateFileAsync and Windows.Storage.FileIO.WriteTextAsync, to create and update a file in the roaming app data store. This example creates a file named dataFile.txt in the roamingFolder container and writes the current date and time to the file. The ReplaceExisting value from the CreationCollisionOption enumeration indicates to replace the file if it already exists.
void MainPage::WriteTimestamp() { concurrency::task<StorageFile^> fileOperation = roamingFolder->CreateFileAsync("dataFile.txt", CreationCollisionOption::ReplaceExisting); fileOperation.then([this](StorageFile^ sampleFile) { auto calendar = ref new Calendar; auto now = calendar->ToDateTime(); auto formatter = ref new Windows::Globalization::DateTimeFormatting::DateTimeFormatter("longtime"); return FileIO::WriteTextAsync(sampleFile, formatter->Format(now)); }).then([this](task<void> previousOperation) { try { previousOperation.get(); } catch (Platform::Exception^) { // Timestamp not written } }); }
Read data from a file
Use the file APIs, such as Windows.Storage.StorageFolder.GetFileAsync, Windows.Storage.StorageFile.GetFileFromApplicationUriAsync, and Windows.Storage.FileIO.ReadTextAsync, to open and read a file in the roaming app data store. This example opens the dataFile.txt file created in the previous section and reads the date from the file. For details on loading file resources from various locations, see How to load file resources.
void MainPage::ReadTimestamp() { concurrency::task<StorageFile^> getFileOperation(roamingFolder->GetFileAsync("dataFile.txt")); getFileOperation.then([this](StorageFile^ file) { return FileIO::ReadTextAsync(file); }).then([this](concurrency::task<String^> previousOperation) { String^ timestamp; try { // Data is contained in timestamp timestamp = previousOperation.get(); } catch (...) { // Timestamp not found } }); }
Delete settings when finished with them
Call the ApplicationDataContainerSettings.Remove method to delete the exampleSetting setting from the roamingSettings container when you have finished with it.
// Delete simple setting auto values = roamingSettings->Values; values->Remove("exampleSetting");
Call the ApplicationDataCompositeValue.Remove method to delete the exampleCompositeSetting composite setting from the roamingSettings container when you have finished with it.
Call the ApplicationDataContainer.DeleteContainer method to delete the exampleContainer settings container when you have finished with it.
Roam data across different types of devices
If you publish two versions of your app - a version for Windows Store and a version for Windows Phone Store - you can roam app data across the apps running on the two different types of devices. To roam data across different versions of your app on different types of devices, assign the same Package Family Name (PFN) to each version of the app.
For more info, see How to roam data between a Windows Store app and a Windows Phone Store app.
Remarks
Each app has a quota for roaming app data. Check the ApplicationData.RoamingStorageQuota property to determine the total size of roaming data allowed. If your roaming data exceeds the quota, it won’t roam until its size is less than the quota again.
Related topics
- Tasks
- How to load file resources
- Quickstart: Local app data
- Quickstart: Temporary app data
- Conceptual
- Accessing app data with the Windows Runtime
- Guidelines
- Guidelines for roaming app data
- Reference
- Windows.Storage.ApplicationData
- Windows.Storage.ApplicationDataCompositeValue
- Windows.Storage.ApplicationDataContainer
- Windows.Storage.ApplicationDataContainerSettings
- Samples
- Application data sample