Azure.Messaging.EventHubs (.NET)

High-throughput event streaming SDK for sending and receiving events via Azure Event Hubs.

Installation

# Core package (sending and simple receiving)
dotnet add package Azure.Messaging.EventHubs

# Processor package (production receiving with checkpointing)
dotnet add package Azure.Messaging.EventHubs.Processor

# Authentication
dotnet add package Azure.Identity

# For checkpointing (required by EventProcessorClient)
dotnet add package Azure.Storage.Blobs

Current Versions: Azure.Messaging.EventHubs v5.12.2, Azure.Messaging.EventHubs.Processor v5.12.2

Environment Variables

EVENTHUB_FULLY_QUALIFIED_NAMESPACE=<namespace>.servicebus.windows.net
EVENTHUB_NAME=<event-hub-name>

# For checkpointing (EventProcessorClient)
BLOB_STORAGE_CONNECTION_STRING=<storage-connection-string>
BLOB_CONTAINER_NAME=<checkpoint-container>

# Alternative: Connection string auth (not recommended for production)
EVENTHUB_CONNECTION_STRING=Endpoint=sb://<namespace>.servicebus.windows.net/;SharedAccessKeyName=...

Authentication

using Azure.Identity;
using Azure.Messaging.EventHubs;
using Azure.Messaging.EventHubs.Producer;

// Always use DefaultAzureCredential for production
var credential = new DefaultAzureCredential();

var fullyQualifiedNamespace = Environment.GetEnvironmentVariable("EVENTHUB_FULLY_QUALIFIED_NAMESPACE");
var eventHubName = Environment.GetEnvironmentVariable("EVENTHUB_NAME");

var producer = new EventHubProducerClient(
    fullyQualifiedNamespace,
    eventHubName,
    credential);

Required RBAC Roles:

• Sending: Azure Event Hubs Data Sender
• Receiving: Azure Event Hubs Data Receiver
• Both: Azure Event Hubs Data Owner

Client Types

Client	Purpose	When to Use
EventHubProducerClient	Send events immediately in batches	Real-time sending, full control over batching
EventHubBufferedProducerClient	Automatic batching with background sending	High-volume, fire-and-forget scenarios
EventHubConsumerClient	Simple event reading	Prototyping only, NOT for production
EventProcessorClient	Production event processing	Always use this for receiving in production

Core Workflow

1. Send Events (Batch)

using Azure.Identity;
using Azure.Messaging.EventHubs;
using Azure.Messaging.EventHubs.Producer;

await using var producer = new EventHubProducerClient(
    fullyQualifiedNamespace,
    eventHubName,
    new DefaultAzureCredential());

// Create a batch (respects size limits automatically)
using EventDataBatch batch = await producer.CreateBatchAsync();

// Add events to batch
var events = new[]
{
    new EventData(BinaryData.FromString("{\"id\": 1, \"message\": \"Hello\"}")),
    new EventData(BinaryData.FromString("{\"id\": 2, \"message\": \"World\"}"))
};

foreach (var eventData in events)
{
    if (!batch.TryAdd(eventData))
    {
        // Batch is full - send it and create a new one
        await producer.SendAsync(batch);
        batch = await producer.CreateBatchAsync();
        
        if (!batch.TryAdd(eventData))
        {
            throw new Exception("Event too large for empty batch");
        }
    }
}

// Send remaining events
if (batch.Count > 0)
{
    await producer.SendAsync(batch);
}

2. Send Events (Buffered - High Volume)

using Azure.Messaging.EventHubs.Producer;

var options = new EventHubBufferedProducerClientOptions
{
    MaximumWaitTime = TimeSpan.FromSeconds(1)
};

await using var producer = new EventHubBufferedProducerClient(
    fullyQualifiedNamespace,
    eventHubName,
    new DefaultAzureCredential(),
    options);

// Handle send success/failure
producer.SendEventBatchSucceededAsync += args =>
{
    Console.WriteLine($"Batch sent: {args.EventBatch.Count} events");
    return Task.CompletedTask;
};

producer.SendEventBatchFailedAsync += args =>
{
    Console.WriteLine($"Batch failed: {args.Exception.Message}");
    return Task.CompletedTask;
};

// Enqueue events (sent automatically in background)
for (int i = 0; i < 1000; i++)
{
    await producer.EnqueueEventAsync(new EventData($"Event {i}"));
}

// Flush remaining events before disposing
await producer.FlushAsync();

3. Receive Events (Production - EventProcessorClient)

using Azure.Identity;
using Azure.Messaging.EventHubs;
using Azure.Messaging.EventHubs.Consumer;
using Azure.Messaging.EventHubs.Processor;
using Azure.Storage.Blobs;

// Blob container for checkpointing
var blobClient = new BlobContainerClient(
    Environment.GetEnvironmentVariable("BLOB_STORAGE_CONNECTION_STRING"),
    Environment.GetEnvironmentVariable("BLOB_CONTAINER_NAME"));

await blobClient.CreateIfNotExistsAsync();

// Create processor
var processor = new EventProcessorClient(
    blobClient,
    EventHubConsumerClient.DefaultConsumerGroup,
    fullyQualifiedNamespace,
    eventHubName,
    new DefaultAzureCredential());

// Handle events
processor.ProcessEventAsync += async args =>
{
    Console.WriteLine($"Partition: {args.Partition.PartitionId}");
    Console.WriteLine($"Data: {args.Data.EventBody}");
    
    // Checkpoint after processing (or batch checkpoints)
    await args.UpdateCheckpointAsync();
};

// Handle errors
processor.ProcessErrorAsync += args =>
{
    Console.WriteLine($"Error: {args.Exception.Message}");
    Console.WriteLine($"Partition: {args.PartitionId}");
    return Task.CompletedTask;
};

// Start processing
await processor.StartProcessingAsync();

// Run until cancelled
await Task.Delay(Timeout.Infinite, cancellationToken);

// Stop gracefully
await processor.StopProcessingAsync();

4. Partition Operations

// Get partition IDs
string[] partitionIds = await producer.GetPartitionIdsAsync();

// Send to specific partition (use sparingly)
var options = new SendEventOptions
{
    PartitionId = "0"
};
await producer.SendAsync(events, options);

// Use partition key (recommended for ordering)
var batchOptions = new CreateBatchOptions
{
    PartitionKey = "customer-123"  // Events with same key go to same partition
};
using var batch = await producer.CreateBatchAsync(batchOptions);

EventPosition Options

Control where to start reading:

// Start from beginning
EventPosition.Earliest

// Start from end (new events only)
EventPosition.Latest

// Start from specific offset
EventPosition.FromOffset(12345)

// Start from specific sequence number
EventPosition.FromSequenceNumber(100)

// Start from specific time
EventPosition.FromEnqueuedTime(DateTimeOffset.UtcNow.AddHours(-1))

ASP.NET Core Integration

// Program.cs
using Azure.Identity;
using Azure.Messaging.EventHubs.Producer;
using Microsoft.Extensions.Azure;

builder.Services.AddAzureClients(clientBuilder =>
{
    clientBuilder.AddEventHubProducerClient(
        builder.Configuration["EventHub:FullyQualifiedNamespace"],
        builder.Configuration["EventHub:Name"]);
    
    clientBuilder.UseCredential(new DefaultAzureCredential());
});

// Inject in controller/service
public class EventService
{
    private readonly EventHubProducerClient _producer;
    
    public EventService(EventHubProducerClient producer)
    {
        _producer = producer;
    }
    
    public async Task SendAsync(string message)
    {
        using var batch = await _producer.CreateBatchAsync();
        batch.TryAdd(new EventData(message));
        await _producer.SendAsync(batch);
    }
}

Best Practices

1. Use EventProcessorClient for receiving — Never use EventHubConsumerClient in production
2. Checkpoint strategically — After N events or time interval, not every event
3. Use partition keys — For ordering guarantees within a partition
4. Reuse clients — Create once, use as singleton (thread-safe)
5. Use await using — Ensures proper disposal
6. Handle ProcessErrorAsync — Always register error handler
7. Batch events — Use CreateBatchAsync() to respect size limits
8. Use buffered producer — For high-volume scenarios with automatic batching

Error Handling

using Azure.Messaging.EventHubs;

try
{
    await producer.SendAsync(batch);
}
catch (EventHubsException ex) when (ex.Reason == EventHubsException.FailureReason.ServiceBusy)
{
    // Retry with backoff
    await Task.Delay(TimeSpan.FromSeconds(5));
}
catch (EventHubsException ex) when (ex.IsTransient)
{
    // Transient error - safe to retry
    Console.WriteLine($"Transient error: {ex.Message}");
}
catch (EventHubsException ex)
{
    // Non-transient error
    Console.WriteLine($"Error: {ex.Reason} - {ex.Message}");
}

Checkpointing Strategies

Strategy	When to Use
Every event	Low volume, critical data
Every N events	Balanced throughput/reliability
Time-based	Consistent checkpoint intervals
Batch completion	After processing a logical batch

// Checkpoint every 100 events
private int _eventCount = 0;

processor.ProcessEventAsync += async args =>
{
    // Process event...
    
    _eventCount++;
    if (_eventCount >= 100)
    {
        await args.UpdateCheckpointAsync();
        _eventCount = 0;
    }
};

Related SDKs

SDK	Purpose	Install
Azure.Messaging.EventHubs	Core sending/receiving	dotnet add package Azure.Messaging.EventHubs
Azure.Messaging.EventHubs.Processor	Production processing	dotnet add package Azure.Messaging.EventHubs.Processor
Azure.ResourceManager.EventHubs	Management plane (create hubs)	dotnet add package Azure.ResourceManager.EventHubs
Microsoft.Azure.WebJobs.Extensions.EventHubs	Azure Functions binding	dotnet add package Microsoft.Azure.WebJobs.Extensions.EventHubs

When to Use

This skill is applicable to execute the workflow or actions described in the overview.