Sample4_ReadRevisionHistory.md

Read Revision History

This sample demonstrates how to read the revision history of a Configuration Setting in a Configuration Store. To do this, we create a setting, change it twice to create revisions, then read the revision history for that setting using a SettingSelector that uniquely identifies the configuration setting by its key name. The sample uses a configuration setting with a timestamp in the key name to ensure the setting hasn't been used before and thereby minimize the size of the revision history.

To get started, you'll need a connection string to the Azure App Configuration. See the README for links and instructions.

Create a ConfigurationClient

To interact with Azure App Configuration, you need to instantiate a ConfigurationClient. You can use either an endpoint URL and a TokenCredential or a connection string.

For the sample below, you can set connectionString in an environment variable, a configuration setting, or any way that works for your application. The connection string is available from the App Configuration Access Keys view in the Azure Portal.

var client = new ConfigurationClient(connectionString);

Create the configuration setting with several revisions

First, create an initial ConfigurationSetting instance and set it in the Configuration Store.

ConfigurationSetting setting = new ConfigurationSetting($"setting_with_revisions-{DateTime.Now:s}", "v1");
await client.SetConfigurationSettingAsync(setting);

Every time SetConfigurationSettingAsync succeeds, a new revision is created.

setting.Value = "v2";
await client.SetConfigurationSettingAsync(setting);

setting.Value = "v3";
await client.SetConfigurationSettingAsync(setting);

Retrieve revisions of the setting

To asynchronously get all unexpired revisions, call GetRevisionsAsync with a setting selector that has KeyFilter equal to settings.Key. This will retrieve all revisions of this setting in the store. See App Configuration REST API for more information about filtering.

var selector = new SettingSelector { KeyFilter = setting.Key };

Debug.WriteLine("Revisions of the setting: ");
await foreach (ConfigurationSetting settingVersion in client.GetRevisionsAsync(selector))
{
    Console.WriteLine($"Setting was {settingVersion} at {settingVersion.LastModified}.");
}

Retrieve revisions after deletion

Revisions expire automatically and are available even after setting is deleted.

await client.DeleteConfigurationSettingAsync(setting.Key, setting.Label);

await foreach (ConfigurationSetting settingVersion in client.GetRevisionsAsync(selector))
{
    Console.WriteLine($"Setting was {settingVersion} at {settingVersion.LastModified}.");
}