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A consistent, comprehensive, minimal interface to enable .NET applications to use the complete range of features exposed by the ArangoDB REST API.
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readme.md

arangodb-net-standard: The C#/.NET Standard API driver for ArangoDB.

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Description

A consistent, comprehensive, minimal driver for the ArangoDB REST API. Built using .NET Standard 2.0, the library provides .NET Core and .NET Framework applications with the complete range of features exposed by the ArangoDB REST API.


Project Summary

The library does not aim to provide much in the way of abstraction on top of the individual REST API functions offered by ArangoDB but it does aim to provide comprehensive coverage of all of the available options for each of ArangoDB's REST API endpoints.

The driver is built using the standard HttpClient interface for making HTTP requests, along with Json.NET for (de)serialisation to/from CLI types.

In addition the library provides:

  • Support for async/await across every API operation
  • Adherence to common-practice C# naming conventions
  • Consistent approach for each API endpoint

Usage

Installation

Install the latest release of ArangoDBNetStandard on Nuget.

Quick Start

The following examples can be read one after the other to form a complete working example.

Create a database

// You must use the _system database to create databases
using (var systemDbTransport = HttpApiTransport.UsingBasicAuth(
    new Uri("http://localhost:8529/"),
    "_system",
    "root",
    "root"))
{
    var systemDb = new DatabaseApiClient(systemDbTransport);

    // Create a new database with one user.
    await systemDb.PostDatabaseAsync(
        new PostDatabaseBody
        {
            Name = "arangodb-net-standard",
            Users = new List<DatabaseUser>
            {
                new DatabaseUser
                {
                    Username = "jlennon",
                    Passwd = "yoko123"
                }
            }
        });
}

Since we only use the system database once to create another separate database, we've wrapped systemDbTransport in a using block.

In general, if you are connecting to the same database lots of times, you don't want to dispose HttpApiTransport until the end of your application's life.

Create a collection

// Use our new database, with basic auth credentials for the user jlennon.
var transport = HttpApiTransport.UsingBasicAuth(
    new Uri("http://localhost:8529"),
    "arangodb-net-standard",
    "jlennon",
    "yoko123");

var adb = new ArangoDBClient(transport);

// Create a collection in the database
await adb.Collection.PostCollectionAsync(
    new PostCollectionBody
    {
        Name = "MyCollection"
        // A whole heap of other options exist to define key options, 
        // sharding options, etc
    });

Create documents

// Create document in the collection using anonymous type
await adb.Document.PostDocumentAsync(
    "MyCollection",
    new
    {
        MyProperty = "Value"
    });

// Create document in the collection using strong type
await adb.Document.PostDocumentAsync(
    "MyCollection",
    new MyClass
    {
        ItemNumber = 123456,
        Description = "Some item"
    });
Side note on document keys

The document object must not have any _key property if you expect ArangoDB to generate the document key for you. For our examples here, we've used a separate class for creating documents vs fetching them.

MyClass has no _key property:

class MyClass
{
    public long ItemNumber { get; set; }

    public string Description { get; set; }
}

MyClassDocument is a subclass of MyClass which does define the _key property, along with _id and _rev.

class MyClassDocument: MyClass
{
    public string _key { get; set; }

    public string _id { get; set; }

    public string _rev { get; set; }
}

You may or may not find this pattern useful in your own application.

Run an AQL query

// Run AQL query (create a query cursor)
var response = await adb.Cursor.PostCursorAsync<MyClassDocument>(
    @"FOR doc IN MyCollection 
      FILTER doc.ItemNumber == 123456 
      RETURN doc");

MyClassDocument item = response.Result.First();

Patch a document

// Partially update document
await adb.Document.PatchDocumentAsync<object, object>(
    "MyCollection",
    item._key,
    new { Description = "More description" });

Replace a document

// Fully update document
item.Description = "Some item with some more description";
await adb.Document.PutDocumentAsync(
    $"MyCollection/{item._key}",
    item);

API Errors

Any time an endpoint responds with an HTTP status code which is not a "success" code, an ApiErrorException will be thrown. You may wish to wrap your API calls in a try/catch block, and catch ApiErrorException in certain circumstances.

The ApiErrorException object contains the ApiError property, which will hold an instance of ApiErrorResponse with the following structure. ArangoDB has descriptions for the different ErrorNum values in their online documentation.

/// <summary>
/// ArangoDB API error model
/// </summary>
public class ApiErrorResponse
{
    /// <summary>
    /// Whether this is an error response (always true).
    /// </summary>
    public bool Error { get; set; }

    /// <summary>
    /// Error message.
    /// </summary>
    public string ErrorMessage { get; set; }

    /// <summary>
    /// ArangoDB error number.
    /// See https://www.arangodb.com/docs/stable/appendix-error-codes.html for error numbers and descriptions.
    /// </summary>
    public int ErrorNum { get; set; }

    /// <summary>
    /// HTTP status code.
    /// </summary>
    public HttpStatusCode Code { get; set; }
}

Project Conventions

The intention for ArangoDB-net-standard is to expose the ArangoDB REST API as faithfully as possible with a minimal amount of abstraction on top. However:

  • We do use C# property-naming conventions (using PascalCase) when representing ArangoDB objects
  • We do provide template methods with type parameters to support convenient (de)serialization of user data such as ArangoDB documents and edge documents
  • All methods representing REST API calls are declared async

Overall project structure

  • The library is split into individual classes for each REST API entity. For example, DocumentApiClient, CollectionApiClient, etc.
  • Each API client class can be instantiated by passing an instance of IApiClientTransport. A concrete implementation of this interface is provided, HttpApiTransport. You may also plug in your own implementation.
  • The wrapper class ArangoDBClient is instantiated in the same way as the client classes and provides instances of each client class in its properties.
  • Each ArangoDB REST endpoint is exposed as a method on the appropriate API client class.

API Client Method Signatures

A typical method signature is something like:

// This is illustrative, not actually a method in the API
apiClient.PostEntity(string pathParam, PostEntityBody body, PostEntityQuery query = null);
  • Path parameters are always exposed as string arguments, and will come first in the argument list. e.g. pathParam in the example above.
  • Where an endpoint expects some body content, an API model class is used. An instance of the API model will be expected as an argument to the method. This will come after any path arguments. e.g. PostEntityBody instance in the example above.
  • Optional parameters will be exposed as nullable properties. In cases where the body content is an ArangoDB-specific object, properties with null value are ignored and not sent in the request to ArangoDB. In cases where the body content is a user-specified object (e.g. a document or edge document), null values are not ignored.
  • Where query parameters can be used, a class will be used to capture all possible query parameters. e.g. PostEntityQuery instance in the example above.
  • The query argument will be left optional, with a default value null. If no query argument is provided, no query string is included in the request to ArangoDB.
  • Properties of the query class will be nullable and properties of the query class with null values will not be included in the request to ArangoDB.

Transport

ArangoDB-net-standard uses the IApiClientTransport interface to allow for the ability to provide your own transport implementation. This should allow us to develop support for VelocyStream as an alternative transport in future. There are also other reasons you might want to provide a customised transport, to implement features such as:

  • automated retries for failed requests
  • automated failover to a backup ArangoDB instance
  • load-balancing requests to multiple ArangoDB instances

HttpApiTransport

The HttpApiTransport class implements IApiClientTransport and is the standard HTTP transport provided by ArangoDB-net-standard. It supports the Basic Auth and JWT Authentication schemes.

Authentication
Basic Auth

To create HttpApiTransport using Basic Auth supply appropriate base path and credentials to the static UsingBasicAuth method as follows:

var transport = HttpApiTransport.UsingBasicAuth(
    new Uri("http://localhost:8529/"),
    dbName,
    "username",
    "password");
JSON Web Token (JWT)

To create HttpApiTransport using JWT tokens, supply appropriate base path and JWT token to the static UsingJWTAuth method as follows:

var transport = HttpApiTransport.UsingJwtAuth(
    new Uri("http://localhost:8529/"),
    dbName,
    jwtTokenString);

This assumes you already have a JWT token. If you need to get a token from ArangoDB, you'll need to first setup an HttpApiTransport without any credentials, submit a request to ArangoDB to get a JWT token, then call SetJwtToken on the transport. e.g.:

// Create HttpApiTransport with no authentication set
var transport = HttpApiTransport.UsingNoAuth(
  new Uri(arangodbBaseUrl),
  databaseName);
  
// Create AuthApiClient using the no-auth transport
var authClient = new AuthApiClient(transport);

// Get JWT token by submitting credentials
var jwtTokenResponse = await authClient.GetJwtTokenAsync("username", "password");

// Set token in current transport
transport.SetJwtToken(jwtTokenResponse.Jwt);

// Use the transport, which will now be authenticated using the JWT token. e.g.:
var databaseApi = new DatabaseApiClient(transport);
var userDatabasesResponse = await databaseApi.GetUserDatabasesAsync();

Depending on your application's needs, you might want to securely store the token somewhere so you can use it again later. ArangoDB's tokens are valid for a one month duration, so you will need to get a new token at some point. You must handle fetching new tokens and setting them on the transport instance as part of your application.

ArangoDBClient

ArangoDBClient is a wrapper around all of the individual API client classes. By instantiating ArangoDBClient once, you have access to instances of each API client class. With an instance of IApiClientTransport, create ArangoDBClient like so:

var adb = new ArangoDBClient(transport);

Now you can access instances of the individual client classes as properties, e.g.:

// Create a new collection named "TestCollection"
var postCollectionResponse = await adb.Collection.PostCollectionAsync(
  new PostCollectionBody {
    Name = "TestCollection"
  });

// Add a document to "TestCollection"
var docResponse = await adb.Document.PostDocumentAsync(
  "TestCollection", 
  new { TestKey = "TestValue" });

Serialization

ArangoDB-net-standard allows for alternative serializer implementations to be used by implementing the IApiClientSerialization interface. By default, all API clients will use the provided JsonNetApiClientSerialization which uses the Json.NET library. To use an alternative serialization implementation, pass an instance of IApiClientSerialization when instantiating any API client class or the ArangoDBClient class.

In many cases we depend on the behaviour of Json.NET to automatically map JSON properties using camelCase to C# properties defined using PascalCase when deserializing. Any alternative serializer will need to mimic that behaviour in order to deserialize some ArangoDB JSON objects to their C# types.

Contributing

We welcome any contributions from the wider ArangoDB community.

Please discuss via issue, email, or any other method with the owners of this repository before working on something so we can keep everyone on the right track.

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