How to use Shared Access Signature with tables from Windows Azure

Until now we talk about how to use Shared Access Signature on blobs and queues from Windows Azure. Today we will see how we can use Shared Access Signature with tables from Windows Azure.
Using this feature we can give a limited access to a consumer to Windows Azure tables. In the next part we will look over what are the restrictions that can be made using Shared Access Signature:

• The first limitation that we can add is the time range. Based on the time a user can have a limited access to a table. For example a user can have access to a table only from 1st of July until the end of the week.
• We can limit what actions can be done using a Shared Access Signature. The following actions can be specified: add, update, delete and query.
• We can give access to a table or to only a part of a table. This limitation can be done using the partition key and row key. For example we can limit a consumer to have access only to partions keys from pkStart to pkEnd and from row rwStart to rwEnd.
• The last feature is one of the most powerful features that we have on Azure Tables from Shared Access Signature. We can limit access to only to a part of items from a table. For example we can give access only to items from table that have the partition key equal with some value. In this way the user will not be able to see the rest of the content.

We saw until now, how we can use it in theory. Let see now in practice how the code should look likes.

SharedAccessTablePolicy tablePolicy = new SharedAccessTablePolicy()
{
    Permissions = SharedAccessTablePermissions.Query
            | SharedAccessTablePermissions.Add,
    SharedAccessExpiryTime = DateTime.UtcNow + TimeSpan.FromHours(1)
};

At this step we created the policy. We can specify the permissions right and how long the consumer will have access to our table. The partition key and row key limitation can be done only at the last step when we generate the access token.

TablePermissions tablePermissions = new TablePermissions();
tablePermissions.SharedAccessPolicies.Add(
    "Client1",
    tablePolicy);
myTable.SetPermissions(tablePermissions);

In the above code we create the permissions with the given policy and added to our table. At this step is important to know that we can add more than one access policies. Each access policy have a unique name (in my case is “Client1”). Using this name we can change or remove the permissions on a table.

tableToken = myTable.GetSharedAccessSignature(
    new SharedAccessTablePolicy(),
    "Client1",
    10,
    0,
    19,
    100);

This was last step. At this step we generated the table token. We had to specify the name of the policy that we want to use for that token. In this example I specify that the consumer will have access only from the partition key 10 to 19 and from row keys 0 to 100. If I don’t want to limit the access of the user to the table (to have full access to the table) we need to specify null to these values.

tableToken = myTable.GetSharedAccessSignature(
    new SharedAccessTablePolicy(),
    "Client1",
    null,
    null,
    null,
    null);

The use of this access token is very easy and is 1 to 1 to how we have done for the queues.
Until now we saw how to work with Shared Access Signature with blobs, quest and table. The next post will see how we can change or remove an access signature that was already provided to a client.
Tutorials about Shared Access Signature:

1. Overview
2. How to use Shared Access Signature with tables from Windows Azure
3. How to use Shared Access Signature with blobs from Windows Azure
4. How to use Shared Access Signature with queues from Windows Azure
5. How to remove or edit a Shared Access Signature from Windows Azure 
6. Some scenarios when we can use Shared Access Signature from Windows Azure