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title Quickstart - Use Event Grid pull delivery from .NET app
description This quickstart shows you how to send messages to and receive messages from Azure Event Grid namespace topics using the .NET programming language.
ms.topic quickstart
ms.author sonalikaroy
author sonalika-roy
ms.custom
references_regions
devx-track-dotnet
ignite-2023
ms.date 06/19/2024

Quickstart: Send and receive messages from an Azure Event Grid namespace topic (.NET)

In this quickstart, you do the following steps:

  1. Create an Event Grid namespace, using the Azure portal.
  2. Create an Event Grid namespace topic, using the Azure portal.
  3. Create an event subscription, using the Azure portal.
  4. Write a .NET console application to send a set of messages to the topic
  5. Write a .NET console application to receive those messages from the topic.

Note

This quick start provides step-by-step instructions to implement a simple scenario of sending a batch of messages to an Event Grid Namespace Topic and then receiving them. For an overview of the .NET client library, see Azure Event Grid client library for .NET. For more samples, see Event Grid .NET samples on GitHub.

Prerequisites

If you're new to the service, see Event Grid overview before you do this quickstart.

  • Azure subscription. To use Azure services, including Azure Event Grid, you need a subscription. If you don't have an existing Azure account, you can sign up for a free trial.
  • Visual Studio 2022. The sample application makes use of new features that were introduced in C# 10. To use the latest syntax, we recommend that you install .NET 6.0, or higher and set the language version to latest. If you're using Visual Studio, versions before Visual Studio 2022 aren't compatible with the tools needed to build C# 10 projects.

[!INCLUDE event-grid-create-namespace-portal]

[!INCLUDE event-grid-create-namespace-topic-portal]

[!INCLUDE event-grid-create-event-subscriptions-portal]

[!INCLUDE event-grid-passwordless-template-tabbed]

Launch Visual Studio

Launch Visual Studio. If you see the Get started window, select the Continue without code link in the right pane.

Send messages to the topic

This section shows you how to create a .NET console application to send messages to an Event Grid topic.

Create a console application

  1. In Visual Studio, select File -> New -> Project menu.

  2. On the Create a new project dialog box, do the following steps: If you don't see this dialog box, select File on the menu, select New, and then select Project.

    1. Select C# for the programming language.

    2. Select Console for the type of the application.

    3. Select Console App from the results list.

    4. Then, select Next.

      :::image type="content" source="./media/event-grid-dotnet-get-started-events/new-send-project.png" alt-text="Screenshot showing the Create a new project dialog box with C# and Console selected.":::

  3. Enter EventSender for the project name, EventGridQuickStart for the solution name, and then select Next.

    :::image type="content" source="./media/event-grid-dotnet-get-started-events/event-sender.png" alt-text="Screenshot showing the solution and project names in the Configure your new project dialog box.":::

  4. On the Additional information page, select Create to create the solution and the project.

Add the NuGet packages to the project

  1. Select Tools > NuGet Package Manager > Package Manager Console from the menu.

  2. Run the following command to install the Azure.Messaging.EventGrid NuGet package:

    Install-Package Azure.Messaging.EventGrid.Namespaces

Add code to send event to the namespace topic

  1. Replace the contents of Program.cs with the following code. The important steps are outlined, with additional information in the code comments.

    [!IMPORTANT] Update placeholder values (<NAMESPACE-ENDPOINT> , <TOPIC-NAME>, <TOPIC-ACCESS-KEY>) in the code snippet with your namespace endpoint, topic name, and topic key.

    using Azure.Messaging;
using Azure;
using Azure.Messaging.EventGrid.Namespaces;


// TODO: Replace the following placeholders with appropriate values

// Endpoint of the namespace that you can find on the Overview page for your Event Grid namespace. Prefix it with https://.
// Should be in the form: https://namespace01.eastus-1.eventgrid.azure.net. 
var namespaceEndpoint = "<NAMESPACE-ENDPOINT>";

// Name of the topic in the namespace
var topicName = "<TOPIC-NAME>";

// Access key for the topic
var topicKey = "<TOPIC-ACCESS-KEY>";

// Construct the client using an Endpoint for a namespace as well as the access key
var client = new EventGridSenderClient(new Uri(namespaceEndpoint), topicName, new AzureKeyCredential(topicKey));

// Publish a single CloudEvent using a custom TestModel for the event data.
var @ev = new CloudEvent("employee_source", "type", new TestModel { Name = "Bob", Age = 18 });
await client.SendAsync(ev);

// Publish a batch of CloudEvents.

await client.SendAsync(
new[] {
    new CloudEvent("employee_source", "type", new TestModel { Name = "Tom", Age = 55 }),
    new CloudEvent("employee_source", "type", new TestModel { Name = "Alice", Age = 25 })});

Console.WriteLine("Three events have been published to the topic. Press any key to end the application.");
Console.ReadKey();

public class TestModel
{
    public string Name { get; set; }
    public int Age { get; set; }
}

  2. Build the project, and ensure that there are no errors.

  3. Run the program and wait for the confirmation message.

    Three events have been published to the topic. Press any key to end the application.

    [!IMPORTANT] In most cases, it will take a minute or two for the role assignment to propagate in Azure. In rare cases, it may take up to eight minutes. If you receive authentication errors when you first run your code, wait a few moments and try again.

  4. In the Azure portal, follow these steps:

    1. Navigate to your Event Grid namespace.

    2. On the Overview page, you see the number of events posted to the namespace in the chart.

      :::image type="content" source="./media/event-grid-dotnet-get-started-events/event-grid-namespace-metrics.png" alt-text="Screenshot showing the Event Grid Namespace page in the Azure portal." lightbox="./media/event-grid-dotnet-get-started-events/event-grid-namespace-metrics.png":::

Pull messages from the topic

In this section, you create a .NET console application that receives messages from the topic.

Create a project to receive the published CloudEvents

  1. In the Solution Explorer window, right-click the EventGridQuickStart solution, point to Add, and select New Project.
  2. Select Console application, and select Next.
  3. Enter EventReceiver for the Project name, and select Create.
  4. In the Solution Explorer window, right-click EventReceiver, and select Set as a Startup Project.

Add the NuGet packages to the project

  1. Select Tools > NuGet Package Manager > Package Manager Console from the menu.

  2. Run the following command to install the Azure.Messaging.EventGrid NuGet package. Select EventReceiver for the Default project if it's not already set.

    Install-Package Azure.Messaging.EventGrid.Namespaces

    :::image type="content" source="./media/event-grid-dotnet-get-started-events/install-event-grid-package.png" alt-text="Screenshot showing EventReceiver project selected in the Package Manager Console.":::

Add the code to receive events from the topic

In this section, you add code to retrieve messages from the queue.

  1. Within the Program class, add the following code:

    [!IMPORTANT] Update placeholder values (<NAMESPACE-ENDPOINT> , <TOPIC-NAME>, <TOPIC-ACCESS-KEY>, <TOPIC-SUBSCRIPTION-NAME>) in the code snippet with your namespace endpoint, topic name, topic key, topic's subscription name.

    using Azure;
using Azure.Messaging;
using Azure.Messaging.EventGrid.Namespaces;

// TODO: Replace the following placeholders with appropriate values

// Endpoint of the namespace that you can find on the Overview page for your Event Grid namespace
// Example: https://namespace01.eastus-1.eventgrid.azure.net. 
var namespaceEndpoint = "<NAMESPACE-ENDPOINT>"; // Should be in the form: https://namespace01.eastus-1.eventgrid.azure.net. 

// Name of the topic in the namespace
var topicName = "<TOPIC-NAME>";

// Access key for the topic
var topicKey = "<TOPIC-ACCESS-KEY>";

// Name of the subscription to the topic
var subscriptionName = "<TOPIC-SUBSCRIPTION-NAME>";

// Maximum number of events you want to receive
const short MaxEventCount = 3;

// Construct the client using an Endpoint for a namespace as well as the access key
var client = new EventGridReceiverClient(new Uri(namespaceEndpoint), topicName, subscriptionName, new AzureKeyCredential(topicKey));
    
// Receive the published CloudEvents. 
ReceiveResult result = await client.ReceiveAsync(MaxEventCount);

Console.WriteLine("Received Response");
Console.WriteLine("-----------------");

  2. Append the following methods to the end of the Program class.

    // handle received messages. Define these variables on the top.

var toRelease = new List<string>();
var toAcknowledge = new List<string>();
var toReject = new List<string>();

// Iterate through the results and collect the lock tokens for events we want to release/acknowledge/result

foreach (ReceiveDetails detail in result.Details)
{
    CloudEvent @event = detail.Event;
    BrokerProperties brokerProperties = detail.BrokerProperties;
    Console.WriteLine(@event.Data.ToString());

    // The lock token is used to acknowledge, reject or release the event
    Console.WriteLine(brokerProperties.LockToken);
    Console.WriteLine();

    // If the event is from the "employee_source" and the name is "Bob", we are not able to acknowledge it yet, so we release it
    if (@event.Source == "employee_source" && @event.Data.ToObjectFromJson<TestModel>().Name == "Bob")
    {
        toRelease.Add(brokerProperties.LockToken);
    }
    // acknowledge other employee_source events
    else if (@event.Source == "employee_source")
    {
        toAcknowledge.Add(brokerProperties.LockToken);
    }
    // reject all other events
    else
    {
        toReject.Add(brokerProperties.LockToken);
    }
}

// Release/acknowledge/reject the events

if (toRelease.Count > 0)
{
    ReleaseResult releaseResult = await client.ReleaseAsync(toRelease);

    // Inspect the Release result
    Console.WriteLine($"Failed count for Release: {releaseResult.FailedLockTokens.Count}");
    foreach (FailedLockToken failedLockToken in releaseResult.FailedLockTokens)
    {
        Console.WriteLine($"Lock Token: {failedLockToken.LockToken}");
        Console.WriteLine($"Error Code: {failedLockToken.Error}");
        Console.WriteLine($"Error Description: {failedLockToken.ToString}");
    }

    Console.WriteLine($"Success count for Release: {releaseResult.SucceededLockTokens.Count}");
    foreach (string lockToken in releaseResult.SucceededLockTokens)
    {
        Console.WriteLine($"Lock Token: {lockToken}");
    }
    Console.WriteLine();
}

if (toAcknowledge.Count > 0)
{
    AcknowledgeResult acknowledgeResult = await client.AcknowledgeAsync(toAcknowledge);

    // Inspect the Acknowledge result
    Console.WriteLine($"Failed count for Acknowledge: {acknowledgeResult.FailedLockTokens.Count}");
    foreach (FailedLockToken failedLockToken in acknowledgeResult.FailedLockTokens)
    {
        Console.WriteLine($"Lock Token: {failedLockToken.LockToken}");
        Console.WriteLine($"Error Code: {failedLockToken.Error}");
        Console.WriteLine($"Error Description: {failedLockToken.ToString}");
    }

    Console.WriteLine($"Success count for Acknowledge: {acknowledgeResult.SucceededLockTokens.Count}");
    foreach (string lockToken in acknowledgeResult.SucceededLockTokens)
    {
        Console.WriteLine($"Lock Token: {lockToken}");
    }
    Console.WriteLine();
}

if (toReject.Count > 0)
{
    RejectResult rejectResult = await client.RejectAsync(toReject);

    // Inspect the Reject result
    Console.WriteLine($"Failed count for Reject: {rejectResult.FailedLockTokens.Count}");
    foreach (FailedLockToken failedLockToken in rejectResult.FailedLockTokens)
    {
        Console.WriteLine($"Lock Token: {failedLockToken.LockToken}");
        Console.WriteLine($"Error Code: {failedLockToken.Error}");
        Console.WriteLine($"Error Description: {failedLockToken.ToString}");
    }

    Console.WriteLine($"Success count for Reject: {rejectResult.SucceededLockTokens.Count}");
    foreach (string lockToken in rejectResult.SucceededLockTokens)
    {
        Console.WriteLine($"Lock Token: {lockToken}");
    }
    Console.WriteLine();
}

public class TestModel
{
    public string Name { get; set; }
    public int Age { get; set; }
}

  3. In the Solution Explorer window, right-click EventReceiver project, and select Set as Startup project.

  4. Build the project, and ensure that there are no errors.

  5. Run the EventReceiver application and confirmation you see the three events in the output window.

    :::image type="content" source="./media/event-grid-dotnet-get-started-events/receive-output.png" alt-text="Screenshot showing the output from the Receiver app." lightbox="./media/event-grid-dotnet-get-started-events/receive-output.png":::

Clean up resources

Navigate to your Event Grid namespace in the Azure portal, and select Delete on the Azure portal to delete the Event Grid namespace and the topic in it.

Related topics

See .NET API reference.