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CloudBlob.CopyFromBlob Method (CloudBlob, BlobRequestOptions)

Updated: April 24, 2013

[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.]

Copies an existing blob's contents, properties, and metadata to a new blob, with options.

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

Dim instance As CloudBlob
Dim source As CloudBlob
Dim options As BlobRequestOptions

instance.CopyFromBlob(source, options)

public void CopyFromBlob (
	CloudBlob source,
	BlobRequestOptions options



The source blob.


Type: Microsoft.WindowsAzure.StorageClient.BlobRequestOptions

An object that specifies any additional options for the request.

The following code example checks an access condition on the source blob and copies the blob if the condition is met.

static void CopyIfModifiedSince(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 the source blob.
    CloudBlob sourceBlob = blobClient.GetBlobReference("mycontainer/myblob.txt");

    // Get a reference to the destination blob.
    CloudBlob destBlob = blobClient.GetBlobReference("mycontainer/copy-if-modified-since.txt");
    BlobRequestOptions options = new BlobRequestOptions();
    DateTime dt = new DateTime(2012, 9, 1, 0, 0, 0, DateTimeKind.Utc);

        // Copy the source blob to the destination blob 
        // IF the source blob has been modified since 9/1/2012.
        options.CopySourceAccessCondition = AccessCondition.IfModifiedSince(dt.ToUniversalTime());
        destBlob.CopyFromBlob(sourceBlob, options);
    catch (StorageClientException e)
        if (e.StatusCode == HttpStatusCode.PreconditionFailed)
            Console.WriteLine("Access condition not met - blob " + sourceBlob.Uri 
                + " has not been modified since " + dt.ToUniversalTime());
            Console.WriteLine("Error code: " + e.ErrorCode);

The CopyFromBlob method copies the source blob specified in the source parameter to the blob on which this method is called (the destination blob).

Copying a source blob always copies the entire blob; copying a range of bytes or a set of blocks is not supported.

A blob copy operation can take any of the following forms:

  • You can copy a source blob to a destination blob with a different name from that of the source blob. The destination blob can be an existing blob, or a new blob created by the copy operation.

  • You can copy a source blob to a destination blob with the same name, effectively replacing the source blob. Such a copy operation removes any uncommitted blocks and overwrites the blob's metadata.

  • You can copy a snapshot over its base blob. By promoting a snapshot to the position of the base blob, you can restore an earlier version of a blob.

  • You can copy a snapshot to a destination blob with a different name. The resulting destination blob is a writeable blob and not a snapshot.

Copying Blob Properties and Metadata

When a blob is copied, the following system properties are copied to the destination blob with the same values:

The source blob's committed block list is also copied to the destination blob, if the blob is a block blob. Any uncommitted blocks are not copied.

Copying Conditionally

You can specify an access condition to copy the blob only if a condition is met, using the overload that takes an options parameter. To specify a condition on the destination blob, use the AccessCondition property. To specify a condition on the source blob, use the CopySourceAccessCondition property. If the specified condition is not met, the blob is not copied, and the Blob service returns HTTPStatusCode.PreconditionFailed.

Copying a Leased Blob

To copy a leased blob, use the CopyFrom method.

Copying Snapshots

When a source blob is copied, any snapshots of the source blob are not copied to the destination. When a destination blob is overwritten with a copy, any snapshots associated with the destination blob stay intact under its name.

You can perform a copy operation to promote a snapshot blob over its base blob. In this way you can restore an earlier version of a blob. The snapshot remains, but its source is overwritten with a copy that can be both read and written.

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

Development Platforms

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


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