Types of Subscriptions Filter on Windows Azure Service Bus

Service Bus from Windows Azure is a great services to distribute messages to multiple subscribers. A topic can have one or more subscriptions. A message added to the topic will be send to all subscriptions that are register in that moment.
To be able to control what kind of messages are send to each subscription we can define filters. A filter is added on each subscription and specify what messages will be accepted by subscription.
The types of filters that can used are:

Correlation Filter
This is used when you want to accept messages that has a specific correlation value. This value can be set directly to the BrokenMessage and is great if you have messages with different priority or rank.

CorrelationFilter filter = new CorrelationFilter(“low”);
namespaceManager.CreateSubscription(topicPath, subscriptionName, filter);

BrokenMessage message = new BrokenMessage();
message.CorrelationId = “low”;
…

SqlFilter
This filter give us the ability to specify what kind of messages will be accepted in a subsection based on a custom rules. This rule can be related to the properties list of a BrokenMessage that are specific by the producer or system properties (SessionId for example is a system property).
The syntax is very simple and is based on SQL92 standard and T/SQL. If you know to write a query in SQL than you will not have problem to use this filter. The syntax give us the possibility to use = != < > <> IS IN LIKE EXISTS ESCAPE NO + - * / AND OR …
For a normal use this is enough to define rules over subscriptions.

SqlFilter filter = new SqlFilter(“CustomProperty == 1”);
namespaceManager.CreateSubscription(topicPath, subscriptionName, filter);
…
BrokenMessage message = new BrokenMessage();
message.Properties[“CustomProperty”] = 1;

The “user” or “sys” prefix need to be used when you refers to properties that are in different scope. The “sys” refers to properties that are on BrokenMessage (like Correlationid or SessionId).

FalseFilter
This is a filter that can be used to block all the messages to the given subscription. This can be used if you create a subscription and you don’t want to accept message to it (temporarily). Also, this can be used when you have a subscription and you don’t want to receive message anymore to it, but you don’t want to delete it.

FalseFilter filter = new FalseFilter()
namespaceManager.CreateSubscription(topicPath, subscriptionName, filter);
…

TrueFilter
This filter is similar with SqlFilter. It will accept the message that respect the specific rule.

We looked over what kind of filter can be defined over a subscription. I think that FalseFilter can be very useful when you are in production and you need to control what messages are receive by one of subscription. For example in a scenario when a client didn’t pays the monthly subscription and you want to stop temporary his subscription. Is more simple that deleting it or set a SqlFilter – “ 1 <> 1”.

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See http://go.microsoft.com/fwlink/?LinkId=260882 for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

Entity Framework (EF) TransactionScope vs Database.BeginTransaction

In today blog post we will talk a little about a new feature that is available on EF6+ related to Transactions.
Until now, when we had to use transaction we used ‘TransactionScope’. It works great and I would say that is something that is now in our blood.
using (var scope = new TransactionScope(TransactionScopeOption.Required)) { using (SqlConnection conn = new SqlConnection("...")) { conn.Open(); SqlCommand sqlCommand = new SqlCommand(); sqlCommand.Connection = conn; sqlCommand.CommandText = ... sqlCommand.ExecuteNonQuery(); ... } scope.Complete(); } Starting with EF6.0 we have a new way to work with transactions. The new approach is based on Database.BeginTransaction(), Database.Rollback(), Database.Commit(). Yes, no more TransactionScope.
In the followi…

GET call of REST API that contains '/'-slash character in the value of a parameter

Let’s assume that we have the following scenario: I have a public HTTP endpoint and I need to post some content using GET command. One of the parameters contains special characters like “\” and “/”. If the endpoint is an ApiController than you may have problems if you encode the parameter using the http encoder.
using (var httpClient = new HttpClient()) { httpClient.BaseAddress = baseUrl; Task<HttpResponseMessage> response = httpClient.GetAsync(string.Format("api/foo/{0}", "qwert/qwerqwer"))); response.Wait(); response.Result.EnsureSuccessStatusCode(); } One possible solution would be to encode the query parameter using UrlTokenEncode method of HttpServerUtility class and GetBytes method ofUTF8. In this way you would get the array of bytes of the parameter and encode them as a url token.
The following code show to you how you could write the encode and decode methods.
publ…

Cloud as a Story - Vunvulea Radu

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