How to get all rows in Azure table Storage in C#?

Question

I am trying to get a list of all entities inside an azure table.

Any idea of how I would write this query?

Microampere

Are you using any language specific library e.g. .Net Storage Client library? – Skill

I am using the Microsoft.WindowsAzure.Storage library – Microampere

Answer 1

To answer your question, you could do something like the following:

var acc = new CloudStorageAccount(
                         new StorageCredentials("account name", "account key"), true);
var tableClient = acc.CreateCloudTableClient();
var table = tableClient.GetTableReference("table name");
var entities = table.ExecuteQuery(new TableQuery<MyEntity>()).ToList();

However please keep in mind that table service returns a maximum of 1000 entities in a single call to it. If there're more than 1000 entities available in your table, it returns a continuation token which can be used to fetch next set of entities. The ExecuteQuery method actually handles this continuation token internally thus if you want to cancel this operation for any reason, you can't do that.

A better approach would be to use ExecuteQuerySegmented method and have your application deal with the token. Here's the sample code to do so:

var acc = new CloudStorageAccount(
                         new StorageCredentials("account name", "account key"), true);
var tableClient = acc.CreateCloudTableClient();
var table = tableClient.GetTableReference("table name");
TableContinuationToken token = null;
var entities = new List<MyEntity>();
do
{
    var queryResult = table.ExecuteQuerySegmented(new TableQuery<MyEntity>(), token);
    entities.AddRange(queryResult.Results);
    token = queryResult.ContinuationToken;
} while (token != null);

Skill

I was only able to get PartitionKey and RowKey from this. In order to get all properties, you must add: "var entities = table.ExecuteQuery(new TableQuery<MyModel>()).ToList();" (add <MyModel>). This was not obvious to me :) – Stutsman

In this case MyEntity is our own class? so what are the getter or setter are going to be for it? – Rhinarium

Bit confused as to the use of 'false' on the first lines of both sample codes - to be clear, you're actively disabling HTTPS on the connection, right? Why would that be beneficial to peg-back to HTTP? – Brundisium

@BrettRigby...You're correct. It's a bad idea to let the traffic go over http. I have fixed the code. Thanks for bringing it to my attention. – Skill

Answer 2

If you don't need all rows every time, it's more efficient to retrieve items on demand (lazily) by making use of yield:

public async Task<IEnumerable<T>> GetAll<T>(string tableName) where T : class
{
    var table = this.GetCloudTable(tableName);
    TableContinuationToken token = null;
    do
    {
        var q = new TableQuery<T>();
        var queryResult = await table.ExecuteQuerySegmentedAsync(q, token);
        foreach (var item in queryResult.Results)
        {
            yield return item;
        }
        token = queryResult.ContinuationToken;
    } while (token != null);
}

With this approach, you can get all rows, but if you're looping through the results of GetAll() and find what you're looking for, you can just break the loop, and the GetAll() method would stop without retrieving the next rows from the table.

Counterword

Answer 3

With the newer Azure.Data.Tables SDK this is now much shorter, especially when using the System.Linq.Async nuget package. With that you can simplay write:

/// <summary>
/// Returns all rows in the table
/// </summary>
/// <typeparam name="T">Implementation of ITableEntity</typeparam>
/// <param name="tableClient">The authenticated TableClient</param>
/// <returns></returns>
public static async Task<List<T>> GetAllEntitiesAsync<T>(this TableClient tableClient) where T : class, ITableEntity, new()
{
    return await tableClient.QueryAsync<T>(maxPerPage: 1000).ToListAsync().ConfigureAwait(false);
}

Note: by requesting 1000 rows at once (max) the total amount of requests can be drastically reduced.

Source

Jacie

Thank you so much for this! I am new to Azure Functions and Azure Table Storage. I got confused with CloudTable, ClientTable, different libraries, etc. This helped me greatly! – Lavish