Azure Table Storage CreateQuery in .NET Core

Question

I'm porting my existing class library that targets .NET Framework 4.6.2 to .NET Core 1.1.

Looks like some of the methods that are available in .NET Framework version are not there in .NET Core. Two such methods are table.CreateQuery and table.ExecuteQuery.

Here's an existing function that's giving me an error for CreateQuery:

public T Get<T>(string partitionKey, string rowKey, string tableName) where T : ITableEntity, new()
            => getTable(tableName).CreateQuery<T>().Where(r => r.PartitionKey == partitionKey && r.RowKey == rowKey).FirstOrDefault();

How do I create query in .NET Core?

Recollect

In my case was the use of a method instead of standard operators (==, !=, etc) in the predicate. – Jenisejenkel

Answer 1

According to this question: Missing syncronous methods for dotnet core?，NetCore/Netstandard support does not yet include Sync implementation of the APIs.

Since CreateQuery and ExecuteQuery are all Sync method, so we couldn’t use it in .NET Core, you could only use ExecuteQuerySegmentedAsync,TableQuery, Fluent API and handle the continuation token it returns. More details, you could refer to follow codes:

---

Update:

public static void Main(string[] args)
{
    var result = Get<BookTest3>("Aut_Fantasy", "Cert-0000000020", "DifferenetPartitionTest");
    Console.Write(result.PartitionKey);
    Console.Read();
}

public static T Get<T>(string partitionKey, string rowKey, string tableName) where T : ITableEntity, new()
{
    CloudTable table = ConnectToTable(tableName);
    TableQuery<T> employeeQuery = new TableQuery<T>().Where(
        TableQuery.CombineFilters(
            TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, partitionKey),
            TableOperators.And,
            TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.LessThan, rowKey))
        ).Take(1);
    var re = new T();
        TableContinuationToken continuationToken = null;
    do
    {
        Task<TableQuerySegment<T>> employees = table.ExecuteQuerySegmentedAsync(employeeQuery, continuationToken);
        TableQuerySegment<T> employeess = employees.Result;
        re= employeess.FirstOrDefault();
        continuationToken = employeess.ContinuationToken;
    } while (continuationToken != null);
    return re;
}

Hope this could give you some tips.

---

Update code:

public static void Main(string[] args)
{
    var tas = Get<BookTest3>("Aut_Fantasy", "Cert-0000000020", "DifferenetPartitionTest");
    var result = tas.Result;
    Console.Write(result.PartitionKey);
    Console.Read();
}

public async static Task<T> Get<T>(string partitionKey, string rowKey, string tableName) where T : ITableEntity, new()
{
    //new T();
    CloudTable table = ConnectToTable(tableName);
    TableQuery<T> employeeQuery = new TableQuery<T>().Where(
        TableQuery.CombineFilters(
            TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, partitionKey),
            TableOperators.And,
            TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.LessThan, rowKey))
        ).Take(1);
    var re = new T();
        TableContinuationToken continuationToken = null;
    do
    {
        var employees = await table.ExecuteQuerySegmentedAsync(employeeQuery, continuationToken);

        re = employees.FirstOrDefault();
        continuationToken = employees.ContinuationToken;
    } while (continuationToken != null);
    return re;
}

Counterfoil

How do I make my method generic so that I can read any entity i.e. Get<T>, not just BookTest3? I've been looking for some examples for this everywhere but I couldn't find it. The GET method in my code must be useable in any scenario -- meaning it should be able to return any object type. – Recollect

Thank you. I really appreciate it. I don't think the first line new T(); is necessary in the Get method, is it? – Recollect

I have one more question, if I may. Even though we're making an asynchronous call with ExecuteQuerySegmentedAsync(), we don't use await inside the method or async Task<T> in the method header. My business layer methods that calls the Get<T> method are usually async methods so it feels a bit awkward NOT to call the Get<T> with an await even though we're making an asynchronous call inside it. – Recollect

As far as I know, we could also use the async Task<T> in the method header and use the await in the method content, it is as same as my codes, just changed a little codes. – Counterfoil

how can we do the querying wiht linq? – Magdalenamagdalene

According to azure.microsoft.com/pl-pl/resources/samples/… go with Microsoft.Azure.CosmosDB.Table NuGet as it's the one supporting CosmosDB and Azure Tables – Chowchow

Answer 2

I'll tack these handy extension methods on to this post :)

public static async System.Threading.Tasks.Task<IEnumerable<DynamicTableEntity>> ExecuteQueryAsync(this CloudTable table, TableQuery query)
{
    TableContinuationToken token = null;
    var retVal = new List<DynamicTableEntity>();
    do
    {
        var results = await table.ExecuteQuerySegmentedAsync(query, token);
        retVal.AddRange(results.Results);
        token = results.ContinuationToken;
    } while (token != null);

    return retVal;
}

public static async System.Threading.Tasks.Task<IEnumerable<T>> ExecuteQueryAsync<T>(this CloudTable table, TableQuery<T> query) where T : ITableEntity, new()
{
    TableContinuationToken token = null;
    var retVal = new List<T>();
    do
    {
        var results = await table.ExecuteQuerySegmentedAsync(query, token);
        retVal.AddRange(results.Results);
        token = results.ContinuationToken;
    } while (token != null);

    return retVal;
}

They give you back the same functionality but with ExecuteQueryASYNC as the method name

Tailband

please give an example of how to use them – Magdalenamagdalene