CloudBlobDirectory.BeginListBlobsSegmented Method (AsyncCallback, Object)

Storage Client Library NET API

[This topic is part of the Microsoft Azure Storage Client Library 1.7, which has been deprecated. See Storage Client Library for the latest version.]

Begins an asynchronous request to return a result segment containing a collection of blob items.

Namespace: Microsoft.WindowsAzure.StorageClient
Assembly: Microsoft.WindowsAzure.StorageClient (in Microsoft.WindowsAzure.StorageClient.dll)

Usage

Visual Basic
Dim instance As CloudBlobDirectory
Dim callback As AsyncCallback
Dim state As Object
Dim returnValue As IAsyncResult

returnValue = instance.BeginListBlobsSegmented(callback, state)

Syntax

Visual Basic
Public Function BeginListBlobsSegmented ( _
	callback As AsyncCallback, _
	state As Object _
) As IAsyncResult
C#
public IAsyncResult BeginListBlobsSegmented (
	AsyncCallback callback,
	Object state
)
C++
public:
IAsyncResult^ BeginListBlobsSegmented (
	AsyncCallback^ callback, 
	Object^ state
)
J#
JScript

Parameters

callback

The callback delegate that will receive notification when the asynchronous operation completes.

state

A user-defined object that will be passed to the callback delegate.

Return Value

An IAsyncResult that references the asynchronous operation.

Example

The following code example lists the blobs in a blob directory in segments, using the default hierarchical listing.

 Copy Code
static void ListBlobsInDirectoryAsynchronously(Uri blobEndpoint, string accountName, string accountKey)
{
    //Create service client for credentialed access to the Blob service.
    CloudBlobClient blobClient = new CloudBlobClient(blobEndpoint, new StorageCredentialsAccountAndKey(accountName, accountKey));

    //Get a reference to a blob directory.
    CloudBlobDirectory blobDir = blobClient.GetBlobDirectoryReference("myvirtualdir/a/");

    //Begin the operation to return the first segment of blobs, passing the service client to the callback.
    blobDir.BeginListBlobsSegmented(ListBlobsInDirectoryCallback, blobDir);
}

static void ListBlobsInDirectoryCallback(IAsyncResult result)
{
    CloudBlobDirectory blobDir = (CloudBlobDirectory)result.AsyncState;
    //End the operation.
    ResultSegment<IListBlobItem> resultSegment = blobDir.EndListBlobsSegmented(result);

    //Enumerate the blob items.
    foreach (var blobItem in resultSegment.Results)
    {
        Console.WriteLine(blobItem.Uri);
    }

    //Check the continuation token to determine whether there are more results.
    if (resultSegment.ContinuationToken != null)
    {
        //Get the next result segment, returning up to 1000 blobs per operation.
        blobDir.BeginListBlobsSegmented(1000, resultSegment.ContinuationToken, new BlobRequestOptions(), ListBlobsInSegmentsCallback, blobDir);
    }
}

Remarks

The BeginListBlobsSegmented method begins an operation to list blobs in pages. To specify the page size to return, pass in a non-zero value for the maxResults parameter. Passing in zero for the maxResults parameter returns either the maximum number of results available, or the per-operation limit of 5000 results.

If you have specified a page size, you can check the HasMoreResults property to check whether the page is complete. For example, if you have specified a page size of 10,000, a value which exceeds the per-operation limit, HasMoreResults will return true, indicating that the page is not complete. Note that if you have not specified a page size, HasMoreResults will always be false.

If you have not specified a page size, or the value of maxResults is zero, then check the value of the ContinuationToken property to determine whether there are more results to return. The continuation token is non-null as long as there are more results to return from the service.

Call the GetNext method to return the next segment of results from the service.

The objects returned by the listing depend on the type of listing that is being performed. If the UseFlatBlobListing property is set to true, the listing will return an enumerable collection of CloudBlob objects. If UseFlatBlobListing is set to false (the default value), the listing may return a collection containing CloudBlob objects and CloudBlobDirectory objects. The latter case provides a convenience for subsequent enumerations over a virtual blob hierarchy.


Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Platforms

Development Platforms

Windows Vista, Windows 7, Windows Server 2008, Windows 8.1, Windows Server 2012 R2, Windows 8 and Windows Server 2012

Change History

See Also