Dgraph 21.3.1.2

Dgraph.net

This client follows the Dgraph Go client closely.

Before using this client, we highly recommend that you go through dgraph.io/docs, and understand how to run and work with Dgraph.

Use Discuss Issues for reporting issues about this repository.

Table of contents

• Install
• Supported Versions
• Using a client
  • Creating a client
  • Login into a namespace
  • Connecting To Dgraph Cloud
  • Altering the database
  • Creating a transaction
  • Running a mutation
  • Running a query
  • Query with RDF response
  • Running an Upsert: Query + Mutation
  • Running Conditional Upsert
  • Committing a transaction
  • Setting Metadata Headers

Install

Install using nuget:

dotnet add package Dgraph

WARNING: Be aware that there may be other .NET packages with similar names. To verify the official package, please visit https://www.nuget.org/packages/Dgraph. Make sure you are using the correct and official package to avoid potential confusion.

Supported Versions

Depending on the version of Dgraph that you are connecting to, you will have to use a different version of this client.

Using a Client

Most client and transaction methods return a Result object from the FluentResults library. You can check the status of the result by using Result.IsSuccess or Result.IsFailed. Exceptions are contained inside Result.Errors.

Creating a Client

An IDgraphClient can be created with a list of GrpcChannel as objects. Connecting to multiple Dgraph servers in the same cluster allows for better distribution of workload.

The following code snippet shows just one connection.

using Dgraph;
using Grpc.Net.Client;

GrpcChannel channel = GrpcChannel.ForAddress("http://localhost:9080");
using var dgraphClient = DgraphClient.Create(channel);

The connection can be configured by using GrpcChannelOptions.

using Grpc.Net.Client;

var options = new GrpcChannelOptions
{
    CompressionProviders = <...>, // List of Grpc ICompressionProvider
    Credentials = Grpc.Core.ChannelCredentials.Create(<...>)
};
GrpcChannel channel = GrpcChannel.ForAddress("http://localhost:9080", options);

Login into a namespace

If your server has Access Control Lists enabled (Dgraph v1.1 or above), the client must be logged in for accessing data. Use Login to obtain and remember access and refresh JWTs.

var response = await dgraphClient.Login("user", "password");
if (response.IsFailed) {
    // Handle errors
}

All subsequent operations via the logged in client will send along the stored access token.

If your server additionally has namespaces (Dgraph v21.03 or above), use LoginIntoNamespace.

var response = await dgraphClient.LoginIntoNamespace("groot", "password", 123);
if (response.IsFailed) {
    // Handle errors
}

Connecting To Dgraph Cloud

Use DgraphCloudChannel.Create to create a GrpcChannel that connects to a Dgraph Cloud backend.

DgraphCloudChannel.Create can accept GraphQL or gRPC URIs from Dgraph Cloud, but it will always connect via gRPC.

using Dgraph;
using Grpc.Net.Client;

string ENDPOINT = "<...>";
string API_KEY = "<...>";

GrpcChannel channel = DgraphCloudChannel.Create(ENDPOINT, API_KEY);
using var dgraphClient = DgraphClient.Create(channel);

Altering the Database

To set the schema, create an instance of Dgraph.Api.Operation and use the Alter endpoint.

using Dgraph;

var operation = new Api.Operation {
    Schema = "name: string @index(exact) ."
};
var response = await dgraphClient.Alter(operation);
if (response.IsFailed) {
    // Handle errors
}

Operation contains other fields as well, including DropAttr and DropAll. DropAll is useful if you wish to discard all the data without bringing the instance down. DropAttr is used to drop all the data related to a predicate.

Starting in Dgraph version 20.03.0, indexes can be computed in the background. You can set the RunInBackground field to true like so:

using Dgraph;

var operation = new Api.Operation {
    Schema = "name: string @index(exact) .",
    RunInBackground = true
};
var response = await dgraphClient.Alter(operation);
if (response.IsFailed) {
    // Handle errors
}

Creating a Transaction

To create a transaction, call the IDgraphClient.NewTransaction() method, which returns a new ITransaction. This operation incurs no network overhead.

To ensure the ITransaction is properly disposed after it has completed, use the using keyword.

using var transaction = dgraphClient.NewTransaction();
var transactionResponse = await transaction.Mutate(...);
if (transactionResponse.IsFailed) {
    // Handle errors
}
var response = await transaction.Commit();
if (response.IsFailed) {
    // Handle errors
}

Read-only transactions can be created by calling the IDgraphClient.NewReadOnlyTransaction method. Read-only transactions are useful to increase read speed because they can circumvent the usual consensus protocol. Read-only transactions cannot contain mutations. There is nothing to dispose for a ReadOnlyTransaction object, so it does not implement IDisposable.

var readOnlyTransaction = dgraphClient.NewReadOnlyTransaction();
var response = await readOnlyTransaction.Query(...);
if (response.IsFailed) {
    // Handle errors
}

Running a Mutation

ITransaction.Mutate runs a mutation. It takes a Dgraph.Api.Mutation or a MutationBuilder. You can set the data using JSON or RDF N-Quad format.

To use JSON, use the fields SetJson and DeleteJson, which accept a string representing the nodes to be added or removed respectively (either as a JSON map or a list). You can use any library to serialize objects to a JSON string, such as JSON.NET.

To use RDF, use the fields SetNquads and DelNquads, which accept a string representing the valid RDF triples (one per line) to be added or removed respectively.

Dgraph.Api.Mutation also contains the Set and Del fields which accept a list of RDF triples that have already been parsed into our internal format. As such, these fields are mainly used internally and you should use the SetNquads and DelNquads fields instead if you plan on using RDF.

While you can construct a Dgraph.Api.Mutation object directly, it is easier to let MutationBuilder handle implementation details like converting string to Google.Protobuf.ByteString.

using Dgraph;

var transaction = dgraphClient.NewTransaction();
var mutation = new MutationBuilder().SetJson("...").CommitNow();
var response = await transaction.Mutate(mutation);
if (response.IsFailed) {
    // Handle errors
}

If you want to commit a mutation without querying anything further, use MutationBuilder.CommitNow to indicate that the transaction must be immediately committed.

var mutation = new MutationBuilder().SetJson("...").CommitNow();

Multiple mutations can be run in a single request using ITransaction.Do and RequestBuilder. To immediately commit the request, use RequestBuilder.CommitNow.

using Dgraph;

var transaction = dgraphClient.NewTransaction();
var request = new RequestBuilder().WithMutations(
    new MutationBuilder().SetJson("..."),
    new MutationBuilder().SetJson("..."),
    new MutationBuilder().SetJson("..."),
);
var response = await transaction.Do(request);
if (response.IsFailed) {
    // Handle errors
}

Keep in mind that if you do not use RequestBuilder.CommitNow or MutationBuilder.CommitNow, you will still need to manually commit the transaction using ITransaction.Commit.

Check out the example in source/Dgraph.tests.e2e/TransactionTest.cs.

Running a Query

You can run a query by calling ITransaction.Query. You will need to pass in a DQL query string. If you want to pass an additional map of any variables that you might want to set in the query, call ITransaction.QueryWithVars with the variables dictionary as the second argument.

Let’s run the following query with a variable $a:

var query = @"
  query all($a: string) {
    all(func: eq(name, $a)) {
      name
    }
  }";
var varMap = new Dictionary<string, string> { { "$a", "Alice" } };
var response = await transaction.QueryWithVars(query, varMap);
if (response.IsFailed) {
    // Handle errors
}

You can also use ITransaction.Do to run a query.

var query = @"
  query all($a: string) {
    all(func: eq(name, $a)) {
      name
    }
  }";
var varMap = new Dictionary<string, string> { { "$a", "Alice" } };
var request = new RequestBuilder().WithQuery(query).WithVars(varMap);
var response = await transaction.Do(request);
if (response.IsFailed) {
    // Handle errors
}

When running a schema query for predicate name, the schema response is found in the Json field of the transaction response:

var query = @"
  schema(pred: [name]) {
    type
    index
    reverse
    tokenizer
    list
    count
    upsert
    lang
  }";
var response = await transaction.Query(query);
if (response.IsSuccess) {
    Console.WriteLine(response.Value.Json);
}

Query with RDF response

You can get query results as a RDF response by calling ITransaction.QueryRdf. The Rdf field in the response has the encoded RDF result.

Note: If you are querying for only uid values, use a JSON format response.

// Query the balance for Alice and Bob.
var query = @"
  {
    all(func: anyofterms(name, ""Alice Bob"")) {
      name
      balance
    }
  }";
var response = await transaction.QueryRDF(query);
if (response.IsSuccess) {
    // <0x17> <name> "Alice" .
    // <0x17> <balance> 100 .
    Console.WriteLine(response.Value.Rdf);
}

ITransaction.QueryRDFWithVars is also available when you need to pass values for variables used in the query.

Running an Upsert: Query + Mutation

The ITransaction.Do method allows you to run upserts consisting of one query and one mutation. Variables can be defined in the query and used in the mutation.

To know more about upsert, we highly recommend going through the docs at Upsert Block

var query = @"
  query {
    user as var(func: eq(email, ""wrong_email@dgraph.io""))
  }";
var mutation = new MutationBuilder().SetNquads("uid(user) <email> \"correct_email@dgraph.io\" .");
var request = new RequestBuilder()
    .WithQuery(query)
    .WithMutations(mutation)
    .CommitNow();

// Update email only if matching uid found.
var response = await transaction.Do(request);
if (response.IsFailed) {
    // Handle errors
}

Running Conditional Upsert

The upsert block also allows specifying a conditional block using and @if directive. The mutation is executed only when the specified condition is true. If the condition is false, the mutation is silently ignored.

See more about Conditional Upsert here.

var query = @"
  query {
    user as var(func: eq(email, ""wrong_email@dgraph.io""))
  }";
var mutation = new MutationBuilder()
    .Cond("@if(eq(len(user), 1))") // Only mutate if "wrong_email@dgraph.io" belongs to single user.
    .SetNquads("uid(user) <email> ""correct_email@dgraph.io"" .");
var request = new RequestBuilder()
    .WithQuery(query)
    .WithMutations(mutation)
    .CommitNow();

// Update email only if exactly one matching uid found.
var response = await transaction.Do(request);
if (response.IsFailed) {
    // Handle errors
}

Committing a Transaction

A transaction can be committed using the ITransaction.Commit method. If your transaction never submitted any mutations, then ITransaction.Commit is not necessary.

An error will be returned if other transactions running concurrently modify the same data that was modified in this transaction. It is up to the user to retry transactions when they fail.

using var transaction = dgraphClient.NewTransaction();

// Perform some queries and mutations.

var response = await transaction.Commit();
if (response.IsFailed) {
    // Retry or handle errors
}

Setting Metadata Headers

Metadata headers such as authentication tokens can be set through the options argument of gRPC methods. Below is an example of how to set a header named "auth-token".

using Grpc.Core;

var metadata = new Metadata
{
    { "auth-token", "the-auth-token-value" }
};
var options = new CallOptions(headers: metadata);
client.Alter(operation, options);