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Πρόσφατες Δημοσιεύσεις
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At ClipFlair Studio (a Silverlight app), I had some time ago implemented a confirmation warning upon user trying to close the webpage (when it was running inside the web browser), which then had stopped functioning. It seems at some refactoring I had added code like the following: var activityView = activityView(); and it was failing […]...
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What an honor being part of this team running the largest Tech event in Greece. Preparations Read more...
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Προχθές ανακοινώθηκε στην TechEd 2013 ΝΑ η εδώ και καιρό αναμενόμενη έλευση του νέου SQL Server 2014. Πολλά είναι τα νέα χαρακτηριστικά τα οποία έρχονται με αυτή την έκδοση, με κυρίαρχο ρόλο να παίζουν το Hekaton και οι επιπλέον δυνατότητες στο Azure. Για περισσότερα κλίκ στο http://www.sqlschool.gr/blog/sql-server-2014-ante-portas-932.aspx...
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Microsoft.Net.Http was released today as a stable NuGet package. Yep, that’s right: You can finally Read more...
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The other day my Microsoft Wireless Laser Mouse 6000 (was either a gift from Microsoft Hellas or had ordered it myself from Microsoft Company Store with the credit Microsoft used to give pro-crisis to MVPs) started behaving erratically, failing most of the times to right-click and sometimes doing left clicks instead with some delay, or […]...
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If you have an e-mail account @otenet.gr you may find out that when connecting your laptop to another network (say you’re travelling) you can’t send SMTP e-mails. To fix this make sure you set your STMP server settings to use SSL encryption and provide the port number 465 for connection. If you use Outlook (Express) […]...
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In this post we will see a simple code fragment that can be used to detect memory leaks (more specific objects that are not cleaned by the garbage collector) and we will do it in the context of an interesting memory leak that can be created when using event delegates. The memory leak with event delegates Suppose you have an application in WPF with a single window that presents some money values in a specific currency (say EURO). At a specific instance you may have more than one such windows open. Now a requirement comes that defines that you need to be able to change the currency (say from euro to dollar) and have this change be reflected immediately to any currently open window displaying the money value. One easy way to tackle this is shown in the following figure: The "settings" object is static with a static property "Currency" with the current currency and an event called "OnCurrencyChanged" that is fired when the currency is changed. The "Window" class ("window1" nad "window2" objects) defines a method "currencyChanged"....
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Αναμφίβολα όλοι γνωρίζουμε την αξία που έχουν οι indexes σε ένα πίνακα και την ευεργετική επίδραση τους στα queries που γίνονται σε αυτούς.Επίσης όλοι ξέρουν ότι το index fragmentation είναι ένας παράγοντας που έχει αρνητική επίδραση στην αξία των index όμως γνωρίζουν όλοι τι είναι internal και τι external fragmentation; http://www.sqlschool.gr/blog/external-and-internal-index-fragmentation-930.aspx...
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Now that my blogging engine is back on track it’s time for the long awaited Read more...
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In this post we will explore a generic way of handling unpredicatble errors/lost connectivity in our Windows 8 Apps developed with HTML5 and Javascript. The two requirements we need to tackle are as follows: There is a chance that while our application is running, internet connectivity will be lost. We need to know when this happens in order to inform the user and possibly handle the problem while preserving application state. Unpredicatble errors may occur that will cause a general exception. We need to "catch" those errors, informing the user with a generic (and apologetic) error message and maybe transmit some useful details about the error to a service we have implemented for this purpose. Handling internet connectivity problems First we need a way to verify whether the app has connectivity to the internet. This can be done by using the following function: utilities.isConnected=function() { var connectivity=Windows.Networking.Connectivity; var profile = connectivity.NetworkInformation.getInternetConnectionProfile();...
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I can think many reason why Security is necessary when developing even the simplest online shop backend. I will not elaborate them but I will concentrate on how to empower the application prototype we created for our DXSK8 e-shop with a flexible Security System . Note that after this we really close to first paycheck I remind you that in previous post we applied a XAF layer(rich application) over an EF model located in an external lib (DSK8.Service). Now we will extend the same EF model to support XAF’s Security System . 1) Design Entity Framework Model for the Security System objects. XAF’s Security system uses Users, Roles and Permissions to configure both the data access and the UI generation for both platforms! This is done with the help of a few system interfaces such as : User: ISecurityUser , IAuthenticationStandardUser , IOperationPermissionProvider Role:, IOperationPermissionProvider . Our EF model from the DXSK8.Service project already contains an Employee entity which is perfect to take the role of...
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One of our ClipFlair Studio users reported on having some issue trying to install Silverlight on MacOS-X, so I gathered some related info below: First of all, at the Silverlight installation webpage, at the System Requirements tab, you can find the following requirements: Macintosh (Intel-based) Intel Core Duo 1.83-gigahertz (GHz) or higher processor […]...
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One of the first things you may find yourself wondering about when creating an Azure SQL database is how to have ASPNETDB installed in. If you try to use aspnet_regsql you will be frustrated by the error: Setup failed . Exception : An error occurred during the execution of the SQL file 'InstallCommon.sql' . The SQL error number is 40508 and the SqlException message is : USE statement is not supported to switch between databases . Use a new connection to connect to a different Database . which means SQL Azure simply does not support the USE statement , really. Fortunately, Microsoft has created a hotfix to work around this problem. Download and extract the contents of aspnet_regsqlazure.zip then open a command prompt and navigate to the folder where you extracted the files. Enter the following command to have the job done: aspnet_regsqlazure - s [ your server name ]. database . windows . net - d [ your database name ] - u [ your user name ]@[ your server name ] - p [ your password ] - a mr...
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In my previous post I wrote about using Linq-to-Sql and the Repository pattern. Typically, this means the dbml file is located in a repository project, which is a separate library project. In other words, the dbml files does not have direct access to the web.config connection strings of your web (presentation) project. The dbml designer is configured using the app.config settings, instead. On the other hand, the web.config debug/release build mechanism is too handy to ignore when it comes to connection strings. So, can the dbml be programmatically configured to use the appropriate web.config's connection string and if yes, how? The answer lies in the connection string passed as a parameter to the DataContext constructor thus overriding the dbml designer's property. This becomes even easier when using the Repository pattern since there is a single point of construction: the Repository class constructor. The following code snipet demonstrates the solution discussed. Please note, that the presented abstract Repository...
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As you may have already read, a couple of months back I migrated my blog Read more...
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In Part 1 of this series I’ve shown you how easy it was to build Read more...
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I’ve been using RSS feed aggregators most of my life and have tried pretty much Read more...
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Όλο και περισσότερες είναι πλέον οι πηγές που περιέχουν δεδομένα. Αυτό σημαίνει ότι όλο και περισσότερο υπάρχει η ανάγκη συγκερασμού αυτών ώστε να βγει μια πληροφορία τέτοια που να οδηγεί σε μια απόφαση. Σε αυτή την διαδικασία δεν υπάρχει τίποτα καλύτερο από τα Integration Services. Σε αυτό SQL Saturday Night θα ξεκινήσουμε την περιήγηση μας σε αυτά για όσους είτε δεν έχουν ασχοληθεί καθόλου μαζί τους είτε έχουν ελάχιστη επαφή με αυτά. Ημερομηνία διεξαγωγής 25/05/2013 και ώρα 22:00 από το σπίτι σας και τον υπολογιστή σας! http://www.sqlschool.gr/SqlSaturdayNight/20/Content.aspx...
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Στην καθημερινότητα μας όλοι ερχόμαστε, κάποια στιγμή, αντιμέτωποι με προβλήματα που αφορούν την απόδοση του SQL Server. Έχω δεχθεί κατά καιρούς ερωτήματα από πολλούς που αφορούσαν τέτοια θέματα. Μέχρι σήμερα, αν και το έχω αναφέρει αρκετές φορές, δεν είχα γράψει κάτι σχετικά με το πως θα φτάσουμε στην αιτία που μας δημιουργεί το εκάστοτε πρόβλημα απόδοσης, πότε όμως δεν είναι αργά. περισσότερα...
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Great news arrived this week, I’ve been selected to participate as a product subject matter expert Read more...
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XAF already provides strong and flexible validation for any object that fits specified Rules with build-in the Validation Module . In this post you can find a sample XAF application which extends the Validation to provide support for Warning/Information messages. The implementation uses any Validation Business Rule that exists in XAF’s Application Model . Below we see the default ones but its applicable to custom business rules as well. The sample code extends the Application Model of IModelRuleBase and by using one more property like RuleType marks the rule as warning or information as shown: When the Validation occurs this implementation will not raise exceptions for Warning and Information Rules and will change their notification icon accordingly. Windows Web By default, it is also possible to create business rules that evaluated when an object is changed by using the ObjectSpaceObjectChanged custom context (see also Contextual Validation Concepts ). To use this RuleType functionality discussed today...
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Αν και δεν είναι κάτι το συνηθισμένο εντούτοις κάποια στιγμή θα σας έχει έρθει ή θα σας έρθει η ανάγκη για κάτι σαν αυτό που θα σας δώσω σαν tip στο συγκεκριμένο post. Έχω ένα πίνακα που έχει Ν πλήθος εγγραφών και θέλω σε ένα πεδίο του να πάρω όλες τις τιμές του από αυτές τις εγγραφές και να τις έχω σαν ένα πεδίο. Με άλλα λόγια θέλω να κάνω string concatenate more...
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Όταν γράφω ένα post ευελπιστώ να διαβαστεί αρκετές φορές και συνήθως έτσι γίνεται και είναι ένα μέρος της προσωπικής ικανοποίησης που νιώθω. Αν όμως αυτό έχει κάνει κάποιον να προβληματιστεί και να έχει απορίες πάνω σε αυτό και μου τις στείλει μου αρέσει ακόμα περισσότερο. Στο προηγούμενο μου post μίλησα για το πως μπορούμε να καθαρίζουμε τα log entries από τα job executions που έχουμε δημιουργήσει με σκοπό να κρατάμε μόνο αυτά για το χρονικό διάστημα που επιθυμούμε. Ένα φίλος λοιπόν πήγε να εφαρμόσει τα λεγόμενα του post σε SQL Server 2000 και όπως είναι φυσικό δεν μπορούσε να το κάνει καθώς η συγκεκριμένη διαδικασία δεν υπήρχε στο SQL Server 2000. more...
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Μέσα στην καθημερινότητα ενός DBA είναι να έχει αρκετά schedule tasks με τα οποία κάνει την ζωή του ευκολότερη. Αυτά όπως είναι γνωστό εκτελούνται με την χρήση του SQL Server Agent service. Τα tasks αυτά σε κάθε κύκλο εκτέλεσης τους κάνουν logging την κάθε εκτέλεση σε ένα system table που υπάρχει μέσα στην msdb database και αυτός είναι ο dbo.sysjobhistory. Φυσικό είναι ο πίνακας αυτός να γεμίζει με εγγραφές που έπειτα από κάποιο χρονικό διάστημα πρακτικά είναι άχρηστες καθώς αναφέρονται σε εκτελέσεις που αφορούν το πολύ μακρινό παρελθόν. Πως λοιπόν θα σβήσουμε από αυτόν τον πίνακα τις εγγραφές αυτές που δεν θέλουμε; more...
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Imagine that we have already build a mobile app using DXTREME such as the DXSK8 demo and already have a ready-to-use Entity Framework data model. Now we are faced with a task to provide a rich administrative application that will be mainly used in Intranet from the desktop (Windows) or web browser. This application should have a typical CRUD UI for managing goods in an online shop, content on our main web site, etc. and of course have potential for future extensibility and customization by a customer request. Following the instructions of this post it should be easy to do it your self from scratch in less than five minutes! (Sample app at then end of this post). 1) Create a XAF Cross-platform application Create a new XAF solution called DXSK8.Admin by using the DXperience v12.2 XAF Cross-Platform Application project template as shown below. Below we see the created solution which contains two ready to run XAF applications ( DXSK8.Admin.Win, DXSK8.Admin.Web ) and three empty XAF modules where the DXSK8.Admin.Module...
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