Page through a collection using the Microsoft Graph SDKs

For performance reasons, collections of entities are often split into pages and each page is returned with a URL to the next page. The PageIterator class simplifies consuming of paged collections. PageIterator handles enumerating the current page and requesting subsequent pages automatically.

Request headers

If you send any additional request headers in your initial request, those headers are not included by default in subsequent page requests. If those headers need to be sent on subsequent requests, you must set them explicitly.

Iterate over all the messages

The following example shows iterating over all the messages in a user's mailbox.

Tip

This example sets a small page size using the top parameter for demonstration purposes. You can set the page size up to 999 to minimize the number of requests that are necessary.

C#

var messages = await graphClient.Me.Messages
    .GetAsync(requestConfiguration =>
    {
        requestConfiguration.QueryParameters.Top = 10;
        requestConfiguration.QueryParameters.Select =
            new string[] { "sender", "subject", "body" };
        requestConfiguration.Headers.Add(
            "Prefer", "outlook.body-content-type=\"text\"");
    });

if (messages == null)
{
    return;
}

var pageIterator = PageIterator<Message, MessageCollectionResponse>
    .CreatePageIterator(
        graphClient,
        messages,
        // Callback executed for each item in
        // the collection
        (msg) =>
        {
            Console.WriteLine(msg.Subject);
            return true;
        },
        // Used to configure subsequent page
        // requests
        (req) =>
        {
            // Re-add the header to subsequent requests
            req.Headers.Add("Prefer", "outlook.body-content-type=\"text\"");
            return req;
        });

await pageIterator.IterateAsync();

Go

import (
    "context"
    "fmt"
    "log"
    "time"

    abstractions "github.com/microsoft/kiota-abstractions-go"
    graph "github.com/microsoftgraph/msgraph-sdk-go"
    graphcore "github.com/microsoftgraph/msgraph-sdk-go-core"
    "github.com/microsoftgraph/msgraph-sdk-go/models"
    "github.com/microsoftgraph/msgraph-sdk-go/users"
)

headers := abstractions.NewRequestHeaders()
headers.Add("Prefer", "outlook.body-content-type=\"text\"")

var pageSize int32 = 10
query := users.ItemMessagesRequestBuilderGetQueryParameters{
    Select: []string{"body", "sender", "subject"},
    Top:    &pageSize,
}

options := users.ItemMessagesRequestBuilderGetRequestConfiguration{
    Headers:         headers,
    QueryParameters: &query,
}

result, err := graphClient.Me().Messages().Get(context.Background(), &options)
if err != nil {
    log.Fatalf("Error getting messages: %v\n", err)
}

// Initialize iterator
pageIterator, err := graphcore.NewPageIterator[*models.Message](
    result,
    graphClient.GetAdapter(),
    models.CreateMessageCollectionResponseFromDiscriminatorValue)
if err != nil {
    log.Fatalf("Error creating page iterator: %v\n", err)
}

// Any custom headers sent in original request should also be added
// to the iterator
pageIterator.SetHeaders(headers)

// Iterate over all pages
err = pageIterator.Iterate(
    context.Background(),
    func(message *models.Message) bool {
        fmt.Printf("%s\n", *message.GetSubject())
        // Return true to continue the iteration
        return true
    })
if err != nil {
    log.Fatalf("Error iterating over messages: %v\n", err)
}

Java

Note

The Microsoft Graph Java SDK does not currently have a PageIterator class. Instead, you need to request each page as shown in the following code.

MessageCollectionPage messagesPage = graphClient.me().messages()
    .buildRequest(
        new HeaderOption("Prefer", "outlook.body-content-type=\"text\""))
    .select("sender,subject,body").top(10).get();

while (messagesPage != null) {
    final List<Message> messages = messagesPage.getCurrentPage();
    for (Message message : messages) {
        System.out.println(message.subject);
    }

    // Get the next page
    final MessageCollectionRequestBuilder nextPage = messagesPage.getNextPage();
    if (nextPage == null) {
        break;
    } else {
        messagesPage = nextPage.buildRequest(
            // Re-add the header to subsequent requests
            new HeaderOption("Prefer", "outlook.body-content-type=\"text\""))
            .get();
    }
}

TypeScript

const response: PageCollection = await graphClient
  .api('/me/messages?$top=10&$select=sender,subject,body')
  .header('Prefer', 'outlook.body-content-type="text"')
  .get();

// A callback function to be called for every item in the collection.
// This call back should return boolean indicating whether not to
// continue the iteration process.
const callback: PageIteratorCallback = (message: Message) => {
  console.log(message.subject);
  return true;
};

// A set of request options to be applied to
// all subsequent page requests
const requestOptions: GraphRequestOptions = {
  // Re-add the header to subsequent requests
  headers: {
    Prefer: 'outlook.body-content-type="text"',
  },
};

// Creating a new page iterator instance with client a graph client
// instance, page collection response from request and callback
const pageIterator = new PageIterator(
  graphClient,
  response,
  callback,
  requestOptions
);

// This iterates the collection until the nextLink is drained out.
await pageIterator.iterate();

Stopping and resuming the iteration

Some scenarios require stopping the iteration process in order to perform other actions. It is possible to pause the iteration by returning false from the iteration callback. Iteration can be resumed by calling the resume method on the PageIterator.

C#

int count = 0;
int pauseAfter = 25;

var messages = await graphClient.Me.Messages
    .GetAsync(requestConfiguration =>
    {
        requestConfiguration.QueryParameters.Top = 10;
        requestConfiguration.QueryParameters.Select =
            new string[] { "sender", "subject" };
    });

if (messages == null)
{
    return;
}

var pageIterator = PageIterator<Message, MessageCollectionResponse>
    .CreatePageIterator(
        graphClient,
        messages,
        (msg) =>
        {
            Console.WriteLine(msg.Subject);
            count++;
            // If we've iterated over the limit,
            // stop the iteration by returning false
            return count < pauseAfter;
        });

await pageIterator.IterateAsync();

while (pageIterator.State != PagingState.Complete)
{
    Console.WriteLine("Iteration paused for 5 seconds...");
    await Task.Delay(5000);
    // Reset count
    count = 0;
    await pageIterator.ResumeAsync();
}

Go

import (
    "context"
    "fmt"
    "log"
    "time"

    abstractions "github.com/microsoft/kiota-abstractions-go"
    graph "github.com/microsoftgraph/msgraph-sdk-go"
    graphcore "github.com/microsoftgraph/msgraph-sdk-go-core"
    "github.com/microsoftgraph/msgraph-sdk-go/models"
    "github.com/microsoftgraph/msgraph-sdk-go/users"
)

var pageSize int32 = 10
query := users.ItemMessagesRequestBuilderGetQueryParameters{
    Select: []string{"body", "sender", "subject"},
    Top:    &pageSize,
}

options := users.ItemMessagesRequestBuilderGetRequestConfiguration{
    QueryParameters: &query,
}

result, err := graphClient.Me().Messages().Get(context.Background(), &options)
if err != nil {
    log.Fatalf("Error getting messages: %v\n", err)
}

// Initialize iterator
pageIterator, err := graphcore.NewPageIterator[*models.Message](
    result,
    graphClient.GetAdapter(),
    models.CreateMessageCollectionResponseFromDiscriminatorValue)
if err != nil {
    log.Fatalf("Error creating page iterator: %v\n", err)
}

// Pause iterating after 25
var count, pauseAfter = 0, 25

// Iterate over all pages
err = pageIterator.Iterate(
    context.Background(),
    func(message *models.Message) bool {
        count++
        fmt.Printf("%d: %s\n", count, *message.GetSubject())
        // Once count = 25, this returns false,
        // Which pauses the iteration
        return count < pauseAfter
    })
if err != nil {
    log.Fatalf("Error iterating over messages: %v\n", err)
}

// Pause 5 seconds
fmt.Printf("Iterated first %d messages, pausing for 5 seconds...\n", pauseAfter)
time.Sleep(5 * time.Second)
fmt.Printf("Resuming iteration...\n")

// Resume iteration
err = pageIterator.Iterate(
    context.Background(),
    func(message *models.Message) bool {
        count++
        fmt.Printf("%d: %s\n", count, *message.GetSubject())
        // Return true to continue the iteration
        return true
    })
if err != nil {
    log.Fatalf("Error iterating over messages: %v\n", err)
}

Java

// not supported in java SDK

TypeScript

let count = 0;
const pauseAfter = 25;

const response: PageCollection = await graphClient
  .api('/me/messages?$top=10&$select=sender,subject,body')
  .get();

const callback: PageIteratorCallback = (message: Message) => {
  console.log(message.subject);
  count++;

  // If we've iterated over the limit,
  // stop the iteration by returning false
  return count < pauseAfter;
};

const pageIterator = new PageIterator(graphClient, response, callback);
await pageIterator.iterate();

while (!pageIterator.isComplete()) {
  console.log('Iteration paused for 5 seconds...');
  await new Promise((resolve) => setTimeout(resolve, 5000));

  // Reset count
  count = 0;
  await pageIterator.resume();
}