Update Entity

The Update Entity request may be constructed as follows. Replace myaccount with the name of your storage account, mytable with the name of your table, and myPartitionKey and myRowKey1 with the name of the partition key and row key identifying the entity to be updated:

The address of the entity to be updated may take a number of forms on the request URI. The way to address an entity is specified by the ADO.NET Data Services Framework. For more information, see URI Format for Addressing Resources (ADO.NET Data Services Framework).

Request URI:
http://myaccount.table.core.windows.net/mytable(PartitionKey='myPartitionKey',RowKey='myRowKey1')

Request Headers:
x-ms-version: 2011-08-18
Accept: application/atom+xml,application/xml
Accept-Charset: UTF-8
Content-Type: application/atom+xml
If-Match: *
x-ms-date: Wed, 14 Sep 2011 18:10:24 GMT
Authorization: SharedKeyLite myaccount:u0sWZKmjBD1B7LY/CwXWCnHdqK4B1P4z8hKy9SVW49o=
Content-Length: ###
DataServiceVersion: 1.0;NetFx
MaxDataServiceVersion: 2.0;NetFx

Request Body:
<?xml version="1.0" encoding="utf-8"?>
<entry xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns="http://www.w3.org/2005/Atom">
  <title />
  <updated>2008-09-18T23:46:37.168836Z</updated>
  <author>
    <name />
  </author>
<id>http://myaccount.table.core.windows.net/mytable(PartitionKey='mypartitionkey',RowKey='myrowkey1')</id>
  <content type="application/xml">
    <m:properties>
      <d:Address>Santa Clara</d:Address>
      <d:Age m:type="Edm.Int32">23</d:Age>
      <d:AmountDue m:type="Edm.Double">200.23</d:AmountDue>
      <d:CustomerCode m:type="Edm.Guid">c9da6455-213d-42c9-9a79-3e9149a57833</d:CustomerCode>
      <d:CustomerSince m:type="Edm.DateTime">2008-07-10T00:00:00Z</d:CustomerSince>
      <d:IsActive m:type="Edm.Boolean">false</d:IsActive>
      <d:NumOfOrders m:type="Edm.Int64">255</d:NumOfOrders>
      <d:PartitionKey>mypartitionkey</d:PartitionKey>
      <d:RowKey>myrowkey1</d:RowKey>
      <d:Timestamp m:type="Edm.DateTime">2008-09-18T23:46:36.9557508Z</d:Timestamp>
    </m:properties>
  </content>
</entry>

The response includes an HTTP status code and a set of response headers.

Response Status:
HTTP/1.1 204 No Content

Response Headers:
Proxy-Connection: Keep-Alive
Connection: Keep-Alive
x-ms-request-id: 2c085f8f-11a4-4e1d-bd49-82c6bd87649d
Content-Length: 0
Cache-Control: no-cache
Date: Wed, 14 Sep 2011 18:12:54 GMT
ETag: W/"datetime'2009-03-18T18%3A09%3A54.9308145Z'"
DataServiceVersion: 1.0;NetFx
MaxDataServiceVersion: 2.0;NetFx
Server: Windows-Azure-Table/1.0 Microsoft-HTTPAPI/2.0

Only the account owner may call this operation.

When updating an entity, you must specify the PartitionKey and RowKey system properties as part of the update operation.

An entity's ETag provides default optimistic concurrency for update operations. The ETag value is opaque and should not be read or relied upon. Before an update operation occurs, the Table service verifies that the entity's current ETag value is identical to the ETag value included with the update request. If the values are identical, the Table service determines that the entity has not been modified since it was retrieved, and the update operation proceeds.

If the entity's ETag differs from that specified with the update request, the update operation fails with status code 412 (Precondition Failed). This error indicates that the entity has been changed on the server since it was retrieved. To resolve this error, retrieve the entity again and reissue the request.

To force an unconditional update operation, set the value of the If-Match header to the wildcard character (*) on the request. Passing this value to the operation will override the default optimistic concurrency and ignore any mismatch in ETag values.

If the If-Match header is missing from the request, the service returns status code 400 (Bad Request). A request malformed in other ways may also return 400; for more information, see Table Service Error Codes.

If the request specifies a property with a null value, that property is ignored, the update proceeds, and the existing entity is replaced.

注意事項
You can take advantage of this behavior to remove a property from an entity.

To explicitly type a property, specify the appropriate ADO.NET Data Services type by setting the m:type attribute within the property definition in the Atom feed. For more information about typing properties, see Inserting and Updating Entities.

Any application that can authenticate and send an HTTP PUT request can update an entity.

Note that you can also use the .NET Client Library for ADO.NET Data Services to update an entity.

For information about performing batch update operations, see Performing Entity Group Transactions.

概念