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Azure.Core shared library for .NET

Azure.Core provides shared primitives, abstractions, and helpers for modern .NET Azure SDK client libraries. These libraries follow the Azure SDK Design Guidelines for .NET and can be easily identified by package and namespaces names starting with 'Azure', e.g. Azure.Storage.Blobs. A more complete list of client libraries using Azure.Core can be found here.

Azure.Core allows client libraries to expose common functionality in a consistent fashion, so that once you learn how to use these APIs in one client library, you will know how to use them in other client libraries.

The main shared concepts of Azure.Core (and so Azure SDK libraries using Azure.Core) include:

  • Configuring service clients, e.g. configuring retries, logging.
  • Accessing HTTP response details.
  • Calling long-running operations (LROs).
  • Paging and asynchronous streams (AsyncPageable<T>)
  • Exceptions for reporting errors from service requests in a consistent fashion.
  • Abstractions for representing Azure SDK credentials.

Below, you will find sections explaining these shared concepts in more detail.

Installing

Typically, you will not need to install Azure.Core; it will be installed for you when you install one of the client libraries using it. In case you want to install it explicitly (to implement your own client library, for example), you can find the NuGet package here.

Usage Scenarios and Samples

NOTE: Samples in this file apply only to packages that follow Azure SDK Design Guidelines. Names of such packages usually start with Azure.

Configuring Service Clients Using ClientOptions

Azure SDK client libraries typically expose one or more service client types that are the main starting points for calling corresponding Azure services. You can easily find these client types as their names end with the word Client. For example, BlockBlobClient can be used to call blob storage service, and KeyClient can be used to access KeyVault service cryptographic keys.

These client types can be instantiated by calling a simple constructor, or its overload that takes various configuration options. These options are passed as a parameter that extends ClientOptions class exposed by Azure.Core. Various service specific options are usually added to its subclasses, but a set of SDK-wide options are available directly on ClientOptions.

SecretClientOptions options = new SecretClientOptions()
{
    Retry =
    {
        Delay = TimeSpan.FromSeconds(2),
        MaxRetries = 10,
        Mode = RetryMode.Fixed
    },
    Diagnostics =
    {
        IsLoggingContentEnabled = true,
        ApplicationId = "myApplicationId"
    }
};

SecretClient client = new SecretClient(new Uri("http://example.com"), new DefaultAzureCredential(), options);

More on client configuration in client configuration samples

Accessing HTTP Response Details Using Response<T>

Service clients have methods that can be used to call Azure services. We refer to these client methods service methods. Service methods return a shared Azure.Core type Response<T> (in rare cases its non-generic sibling, a raw Response). This type provides access to both the deserialized result of the service call, and to the details of the HTTP response returned from the server.

// create a client
var client = new SecretClient(new Uri("http://example.com"), new DefaultAzureCredential());

// call a service method, which returns Response<T>
Response<KeyVaultSecret> response = await client.GetSecretAsync("SecretName");

// Response<T> has two main accessors.
// Value property for accessing the deserialized result of the call
KeyVaultSecret secret = response.Value;

// .. and GetRawResponse method for accessing all the details of the HTTP response
Response http = response.GetRawResponse();

// for example, you can access HTTP status
int status = http.Status;

// or the headers
foreach (HttpHeader header in http.Headers)
{
    Console.WriteLine($"{header.Name} {header.Value}");
}

More on response types in response samples

Setting up console logging

To create an Azure SDK log listener that outputs messages to console use AzureEventSourceListener.CreateConsoleLogger method.

// Setup a listener to monitor logged events.
using AzureEventSourceListener listener = AzureEventSourceListener.CreateConsoleLogger();

More on logging in configuration samples

Reporting Errors RequestFailedException

try
{
    KeyVaultSecret properties = client.GetSecret("NonexistentSecret");
}
// handle exception with status code 404
catch (RequestFailedException e) when (e.Status == 404)
{
    // handle not found error
    Console.WriteLine("ErrorCode " + e.ErrorCode);
}

More on handling responses in response samples

Consuming Service Methods Returning AsyncPageable<T>

If a service call returns multiple values in pages it would return Pageable<T>/AsyncPageable<T> as a result. You can iterate over AsyncPageable directly or in pages.

// call a service method, which returns AsyncPageable<T>
AsyncPageable<SecretProperties> response = client.GetPropertiesOfSecretsAsync();

await foreach (SecretProperties secretProperties in response)
{
    Console.WriteLine(secretProperties.Name);
}

More on paged responses in response samples

Consuming Long-Running Operations Using Operation<T>

Some operations take long time to complete and require polling for their status. Methods starting long-running operations return *Operation<T> types.

The WaitForCompletionAsync method is an easy way to wait for operation completion and get the resulting value.

// create a client
SecretClient client = new SecretClient(new Uri("http://example.com"), new DefaultAzureCredential());

// Start the operation
DeleteSecretOperation operation = client.StartDeleteSecret("SecretName");

Response<DeletedSecret> response = await operation.WaitForCompletionAsync();
DeletedSecret value = response.Value;

Console.WriteLine(value.Name);
Console.WriteLine(value.ScheduledPurgeDate);

More on long-running operations in long-running operation samples

Mocking

One of the most important cross-cutting features of our new client libraries using Azure.Core is that they are designed for mocking. Mocking is enabled by:

  • providing a protected parameterless constructor on client types.
  • making service methods virtual.
  • providing APIs for constructing model types returned from virtual service methods. To find these factory methods look for types with the ModelFactory suffix, e.g. SecretModelFactory.

For example, the ConfigurationClient.Get method can be mocked (with Moq) as follows:

// Create a mock response
var mockResponse = new Mock<Response>();

// Create a mock value
var mockValue = SecretModelFactory.KeyVaultSecret(
    SecretModelFactory.SecretProperties(new Uri("http://example.com"))
);

// Create a client mock
var mock = new Mock<SecretClient>();

// Setup client method
mock.Setup(c => c.GetSecret("Name", null, default))
    .Returns(Response.FromValue(mockValue, mockResponse.Object));

// Use the client mock
SecretClient client = mock.Object;
KeyVaultSecret secret = client.GetSecret("Name");

More on mocking in mocking samples

Impressions