Is it possible to make count Query for SQl Dependency?

Question

Concerning SignalR and SQL Dependency, is it true that the Query Notification can't use aggregate function like count(*)?

Do one have another way or an idea for create query that contain aggregate function ?

Answer 1

Yes,i have the solution if you want to use aggregate function like count(*) to query sql dependency. First in your repository still use select query . But in the reader you just count the data that reader execute the command. Something like this

int count = 0;
command = new SqlCommand(@"select Edolpuz_DB.dbo.TABEL_KONFIRMASI_PEMBAYARAN.ID_BUKTI_PEMBAYARAN from Edolpuz_DB.dbo.TABEL_KONFIRMASI_PEMBAYARAN where Edolpuz_DB.dbo.TABEL_KONFIRMASI_PEMBAYARAN.IS_NEW = @room", connect);
                command.Parameters.AddWithValue("room", true);
                try
                {
                    command.Notification = null;
                    SqlDependency dependency = new SqlDependency(command);
                    dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
                    if (connect.State == ConnectionState.Open)
                        connect.Close();
                    connect.Open();
                    reader = command.ExecuteReader();
                    while (reader.Read())
                    {
                        count++;
                    }
                    return count;
                }
                catch { return 0; }
                finally { connect.Close(); }

Answer 2

Be careful using SqlDependency class - it has the problems with memory leaks. Hovewer, you can use an open source realization of the SqlDependency class - SqlDependencyEx. It uses a database trigger and native Service Broker notification to receive events about the table changes. This is an usage example:

int changesReceived = 0;
using (SqlDependencyEx sqlDependency = new SqlDependencyEx(
          TEST_CONNECTION_STRING, TEST_DATABASE_NAME, TEST_TABLE_NAME)) 
{
    sqlDependency.TableChanged += (o, e) => changesReceived++;
    sqlDependency.Start();

    // Make table changes.
    MakeTableInsertDeleteChanges(changesCount);

    // Wait a little bit to receive all changes.
    Thread.Sleep(1000);
}

Assert.AreEqual(changesCount, changesReceived);

With SqlDependecyEx you are able to monitor just INSERT or DELETE, avoiding UPDATE, which gives you the desirable result: COUNT-like behavior. Hope this helps.