Orc.Snapshots

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Find the source at https://github.com/WildGums/Orc.Snapshots.

Manage snapshots the easy way using this library.

Quick introduction

Snapshots are like save games. They represent a set of data and/or values from a specific moment in time in an application. Using snapshots allows an application (and thus eventually the end-user) to store data (in memory, in a file or any in other persistence tech) which can later be retrieved.

The advantage of using this library is that it will zip all the data into a single snapshot package. The example below has 3 different providers (they are just examples, it doesn’t have to make sense what they are doing):

• ProjectSnapshotProvider => stores the data in a project to a snapshot
• DateTimeSnapshotProvider => stores the current date/time to a snapshot
• UsernameSnapshotProvider => stores the current username to a snapshot

Whenever a snapshot is created, the SnapshotManager will:

1. Create a zip memory stream
2. For each provider, it will ask the provider to fill up a memory stream which is stored as a separate file
3. Persist the snapshot memory stream to the required persistence store

This will result in the following zip archive:

• Snapshot.zip
  • ProjectSnapshotProvider.zip => contains the zipped memory stream of the snapshot provider
  • DateTimeSnapshotProvider.zip => contains the zipped date/time
  • UsernameSnapshotProvider.zip => contains the zipped username

If the data inside the snapshots needs to be encrypted, it can easily be achieved by implementing a custom ISnapshotStorageService and encrypt the data stream before writing to disk.

Below is an overview of the most important components:

• ISnapshot => the actual snapshot object
• ISnapshotManager => the snapshot manager with events and management methods
• ISnapshotProvider => custom providers that will provide / restore snapshots

Working with snapshot always requires multiple method calls:

1. Create a snapshot
2. Add the snapshot to the manager
3. Save the snapshots

Separate methods were introduced to allow full customized usage of the interaction with the snapshots. There are convenient extension methods that merge multiple method calls into a single call.

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Important note

The base directory will be used as repository. This means that it cannot contain other files and all other files will be deleted from the directory

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Initializing the snapshot manager

Because the snapshot manager is using async, the initialization is a separate method. This gives the developer the option to load the snapshots whenever it is required. To load the stored snapshots from disk, use the code below:

await snapshotManager.LoadAsync(); 

Retrieving a list of all snapshots

var snapshots = snapshotManager.Snapshots;

Creating a snapshot

Storing information in a snapshot is the responsibility of every single component in the application. The ISnapshotManager will gather all the information for the snapshot providers.

Call the following method to create a snapshot.

await snapshotManager.CreateSnapshotAsync("My snapshot title");

Note that a snapshot is only created, not registered in the manager or saved to disk by this method

Providers

Create a provider as shown in the example below:

// TODO: write an example provider

Register the provider in the manager for it to take effect:

snapshotManager.AddProvider(myProvider);

Registering a snapshot and saving all snapshots to disk

To register a snapshot with the manager, use the code below:

await snapshotManager.AddAsync(snapshot);

To save all snapshots, use the code below:

snapshotManager.SaveAsync();

Contributions

We would like to thank the following contributors:

Want to contribute to the documentation? We have a guide for that!

Questions

Have a question about Catel or WildGums controls? Use StackOverflow with the Catel tag!