Quickstart: 2 - Load data to an Azure Search index using C#

This article shows you how to import data into an Azure Search index using C# and the .NET SDK. Pushing documents into your index is accomplished by performing these tasks:

  • Create a SearchIndexClient object to connect to a search index.
  • Create an IndexBatch object containing the documents to be added, modified, or deleted.
  • Call the Documents.Index method on SearchIndexClient to upload documents to an index.


Create an Azure Search index and a SearchServiceClient object, as shown in "Create a client".

Create a client

To import data, you need an instance of the SearchIndexClient class. There are several approaches for creating this class, including using the SearchServiceClient instance that is already created.

As the following example illustrates, you can use the SearchServiceClient instance and call its Indexes.GetClient method. This snippet obtains a SearchIndexClient for the index named "hotels" from a SearchServiceClient named serviceClient.

ISearchIndexClient indexClient = serviceClient.Indexes.GetClient("hotels");

SearchIndexClient has a Documents property. This property provides all the methods you need to add, modify, delete, or query documents in your index.


In a typical search application, querying and indexing are handled separately. While Indexes.GetClient is convenient because you can reuse objects like SearchCredentials, a more robust approach involves creating the SearchIndexClient directly so that you can pass in a query key instead of an admin key. This practice is consistent with the principle of least privilege and helps to make your application more secure. You'll construct a SearchIndexClient in the next exercise. For more information about keys, see Create and manage api-keys for an Azure Search service.

Construct IndexBatch

To import data using the .NET SDK, package up your data into an IndexBatch object. An IndexBatch encapsulates a collection of IndexAction objects, each of which contains a document and a property that tells Azure Search what action to perform on that document (upload, merge, delete, and mergeOrUpload). For more information about indexing actions, see Indexing actions: upload, merge, mergeOrUpload, delete.

Assuming you know which actions to perform on your documents, you are ready to construct the IndexBatch. The example below shows how to create a batch with a few different actions. The example uses a custom class called Hotel that maps to a document in the "hotels" index.

var actions =
    new IndexAction<Hotel>[]
            new Hotel()
                HotelId = "1",
                BaseRate = 199.0,
                Description = "Best hotel in town",
                DescriptionFr = "Meilleur hôtel en ville",
                HotelName = "Fancy Stay",
                Category = "Luxury",
                Tags = new[] { "pool", "view", "wifi", "concierge" },
                ParkingIncluded = false,
                SmokingAllowed = false,
                LastRenovationDate = new DateTimeOffset(2010, 6, 27, 0, 0, 0, TimeSpan.Zero),
                Rating = 5,
                Location = GeographyPoint.Create(47.678581, -122.131577)
            new Hotel()
                HotelId = "2",
                BaseRate = 79.99,
                Description = "Cheapest hotel in town",
                DescriptionFr = "Hôtel le moins cher en ville",
                HotelName = "Roach Motel",
                Category = "Budget",
                Tags = new[] { "motel", "budget" },
                ParkingIncluded = true,
                SmokingAllowed = true,
                LastRenovationDate = new DateTimeOffset(1982, 4, 28, 0, 0, 0, TimeSpan.Zero),
                Rating = 1,
                Location = GeographyPoint.Create(49.678581, -122.131577)
            new Hotel()
                HotelId = "3",
                BaseRate = 129.99,
                Description = "Close to town hall and the river"
        IndexAction.Delete(new Hotel() { HotelId = "6" })

var batch = IndexBatch.New(actions);

In this case, we are using Upload, MergeOrUpload, and Delete as our search actions, as specified by the methods called on the IndexAction class.

Assume that this example "hotels" index is already populated with a number of documents. Note how we did not have to specify all the possible document fields when using MergeOrUpload and how we only specified the document key (HotelId) when using Delete.

Also, note that you can only include up to 1000 documents in a single indexing request.


In this example, we are applying different actions to different documents. If you wanted to perform the same actions across all documents in the batch, instead of calling IndexBatch.New, you could use the other static methods of IndexBatch. For example, you could create batches by calling IndexBatch.Merge, IndexBatch.MergeOrUpload, or IndexBatch.Delete. These methods take a collection of documents (objects of type Hotel in this example) instead of IndexAction objects.

Call Documents.Index

Now that you have an initialized IndexBatch object, you can send it to the index by calling Documents.Index on your SearchIndexClient object. The following example shows how to call Index, as well as some extra steps you will need to perform:

catch (IndexBatchException e)
    // Sometimes when your Search service is under load, indexing will fail for some of the documents in
    // the batch. Depending on your application, you can take compensating actions like delaying and
    // retrying. For this simple demo, we just log the failed document keys and continue.
        "Failed to index some of the documents: {0}",
        String.Join(", ", e.IndexingResults.Where(r => !r.Succeeded).Select(r => r.Key)));

Console.WriteLine("Waiting for documents to be indexed...\n");

Note the try/catch surrounding the call to the Index method. The catch block handles an important error case for indexing. If your Azure Search service fails to index some of the documents in the batch, an IndexBatchException is thrown by Documents.Index. This can happen if you are indexing documents while your service is under heavy load. We strongly recommend explicitly handling this case in your code. You can delay and then retry indexing the documents that failed, or you can log and continue like the sample does, or you can do something else depending on your application's data consistency requirements.

Finally, the code in the example above delays for two seconds. Indexing happens asynchronously in your Azure Search service, so the sample application needs to wait a short time to ensure that the documents are available for searching. Delays like this are typically only necessary in demos, tests, and sample applications.

For more information about document processing, see "How the .NET SDK handles documents".

Next steps

After populating your Azure Search index, the next step is issuing queries to search for documents.