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• To ref or not to ref

  - by nmarun

  So the question is what is the point of passing a reference type along with the ref keyword? I have an Employee class as below: 1: public class Employee 2: { 3: public string FirstName { get; set; } 4: public string LastName { get; set; } 5:  6: public override string ToString() 7: { 8: return string.Format("{0}-{1}", FirstName, LastName); 9: } 10: } In my calling class, I say: 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(Employee employee) 16: { 17: employee.FirstName = "Smith"; 18: employee.LastName = "Doe"; 19: } 20: }   After having a look at the code, you’ll probably say, Well, an instance of a class gets passed as a reference, so any changes to the instance inside the CallSomeMethod, actually modifies the original object. Hence the output will be ‘John-Doe’ on the first call and ‘Smith-Doe’ on the second. And you’re right: So the question is what’s the use of passing this Employee parameter as a ref? 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(ref employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(ref Employee employee) 16: { 17: employee.FirstName = "Smith"; 18: employee.LastName = "Doe"; 19: } 20: } The output is still the same: Ok, so is there really a need to pass a reference type using the ref keyword? I’ll remove the ‘ref’ keyword and make one more change to the CallSomeMethod method. 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(Employee employee) 16: { 17: employee = new Employee 18: { 19: FirstName = "Smith", 20: LastName = "John" 21: }; 22: } 23: } In line 17 you’ll see I’ve ‘new’d up the incoming Employee parameter and then set its properties to new values. The output tells me that the original instance of the Employee class does not change. Huh? But an instance of a class gets passed by reference, so why did the values not change on the original instance or how do I keep the two instances in-sync all the times? Aah, now here’s the answer. In order to keep the objects in sync, you pass them using the ‘ref’ keyword. 1: class Program 2: { 3: static void Main() 4: { 5: Employee employee = new Employee 6: { 7: FirstName = "John", 8: LastName = "Doe" 9: }; 10: Console.WriteLine(employee); 11: CallSomeMethod(ref employee); 12: Console.WriteLine(employee); 13: } 14:  15: private static void CallSomeMethod(ref Employee employee) 16: { 17: employee = new Employee 18: { 19: FirstName = "Smith", 20: LastName = "John" 21: }; 22: } 23: } Viola! Now, to prove it beyond doubt, I said, let me try with another reference type: string. 1: class Program 2: { 3: static void Main() 4: { 5: string name = "abc"; 6: Console.WriteLine(name); 7: CallSomeMethod(ref name); 8: Console.WriteLine(name); 9: } 10:  11: private static void CallSomeMethod(ref string name) 12: { 13: name = "def"; 14: } 15: } The output was as expected, first ‘abc’ and then ‘def’ - proves the 'ref' keyword works here as well. Now, what if I remove the ‘ref’ keyword? The output should still be the same as the above right, since string is a reference type? 1: class Program 2: { 3: static void Main() 4: { 5: string name = "abc"; 6: Console.WriteLine(name); 7: CallSomeMethod(name); 8: Console.WriteLine(name); 9: } 10:  11: private static void CallSomeMethod(string name) 12: { 13: name = "def"; 14: } 15: } Wrong, the output shows ‘abc’ printed twice. Wait a minute… now how could this be? This is because string is an immutable type. This means that any time you modify an instance of string, new memory address is allocated to the instance. The effect is similar to ‘new’ing up the Employee instance inside the CallSomeMethod in the absence of the ‘ref’ keyword. Verdict: ref key came to the rescue and saved the planet… again!

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• How to Automate your Database Documentation

  - by Jonathan Hickford

  In my previous post, “Automating Deployments with SQL Compare command line” I looked at how teams can automate the deployment and post deployment validation of SQL Server databases using the command line versions of Red Gate tools. In this post I’m looking at another use for the command line tools, namely using them to generate up-to-date documentation with every database change. There are many reasons why up-to-date documentation is valuable. For example when somebody new has to work on or administer a database for the first time, or when a new database comes into service. Having database documentation reduces the risks of making incorrect decisions when making changes. Documentation is very useful to business intelligence analysts when writing reports, for example in SSRS. There are a couple of great examples talking about why up to date documentation is valuable on this site:  Database Documentation – Lands of Trolls: Why and How? and Database Documentation Using SQL Doc. The short answer is that it can save you time and reduce risk when you need that most! SQL Doc is a fast simple tool that automatically generates database documentation. It can create documents in HTML, Word or pdf files. The documentation contains information about object definitions and dependencies, along with any other information you want to associate with each object. The SQL Doc GUI, which is included in Red Gate’s SQL Developer Bundle and SQL Toolbelt, allows you to add additional notes to objects, and customise which objects are shown in the docs.  These settings can be saved as a .sqldoc project file. The SQL Doc command line can use this project file to automatically update the documentation every time the database is changed, ensuring that documentation that is always up to date. The simplest way to keep documentation up to date is probably to use a scheduled task to run a script every day. However if you have a source controlled database, or are using a Continuous Integration (CI) server or a build server, it may make more sense to use that instead. If  you’re using SQL Source Control or SSDT Database Projects to help version control your database, you can automatically update the documentation after each change is made to the source control repository that contains your database. To get this automation in place,  you can use the functionality of a Continuous Integration (CI) server, which can trigger commands to run when a source control repository has changed. A CI server will also capture and save the documentation that is created as an artifact, so you can always find the exact documentation for a specific version of the database. This forms an always up to date data dictionary. If you don’t already have a CI server in place there are several you can use, such as the free open source Jenkins or the free starter editions of TeamCity. I won’t cover setting these up in this article, but there is information about using CI servers for automating database tasks on the Red Gate Database Delivery webpage. You may be interested in Red Gate’s SQL CI utility (part of the SQL Automation Pack) which is an easy way to update a database with the latest changes from source control. The PowerShell example below shows how to create the documentation from a database. That database might be your integration database or a shared development database that is always up to date with the latest changes. $serverName = "server\instance" $databaseName = "databaseName" # If you want to document multiple databases use a comma separated list $userName = "username" $password = "password" # Path to SQLDoc.exe $SQLDocPath = "C:\Program Files (x86)\Red Gate\SQL Doc 3\SQLDoc.exe" $arguments = @( "/server:$($serverName)", "/database:$($databaseName)", "/username:$($userName)", "/password:$($password)", "/filetype:html", "/outputfolder:.", # "/project:$args[0]", # If you already have a .sqldoc project file you can pass it as an argument to this script. Values in the project will be overridden with any options set on the command line "/name:$databaseName Report", "/copyrightauthor:$([Environment]::UserName)" ) write-host $arguments & $SQLDocPath $arguments There are several options you can set on the command line to vary how your documentation is created. For example, you can document multiple databases or exclude certain types of objects. In the example above, we set the name of the report to match the database name, and use the current Windows user as the documentation author. For more examples of how you can customise the report from the command line please see the SQL Doc command line documentation If you already have a .sqldoc project file, or wish to further customise the report by including or excluding specific objects, you can use this project on the command line. Any settings you specify on the command line will override the defaults in the project. For details of what you can customise in the project please see the SQL Doc project documentation. In the example above, the line to use a project is commented out, but you can uncomment this line and then pass a path to a .sqldoc project file as an argument to this script.  Conclusion Keeping documentation about your databases up to date is very easy to set up using SQL Doc and PowerShell. By using a CI server to run this process you can trigger the documentation to be run on every change to a source controlled database, and keep historic documentation available. If you are considering more advanced database automation, e.g. database unit testing, change script generation, deploying to large numbers of targets and backup/verification, please email me at [email protected] for further script samples or if you have any questions.

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• Web security course ?

  - by vtortola

  I'd like to do a course about web security. I've seen some certifications that could be interesting: CIW Web Security Professional CISSP® - Certified Information Systems Security Professional Certified Secure Software Lifecycle Professional What do you know about these certifications? are they recognized? I'm not trying to become a hacker, I just want to ensure I have enough knowledge about web security to cope with today internet. From my inexpert point of view, "Certified Secure Software Lifecycle Professional" looks exactly as I want, the problem is that it cost more than 500 bucks! Why certification? well, I want to learn but I would like also have a way to demonstrate to a future employer/customer that I had to study and pass exams, not only attend to a course. Regards.

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• ASP.NET MVC 2 Model Binding for a Collection

  - by nmarun

  Yes, my yet another post on Model Binding (previous one is here), but this one uses features presented in MVC 2. How I got to writing this blog? Well, I’m on a project where we’re doing some MVC things for a shopping cart. Let me show you what I was working with. Below are my model classes: 1: public class Product 2: { 3: public int Id { get; set; } 4: public string Name { get; set; } 5: public int Quantity { get; set; } 6: public decimal UnitPrice { get; set; } 7: } 8:   9: public class Totals 10: { 11: public decimal SubTotal { get; set; } 12: public decimal Tax { get; set; } 13: public decimal Total { get; set; } 14: } 15:   16: public class Basket 17: { 18: public List<Product> Products { get; set; } 19: public Totals Totals { get; set;} 20: } The view looks as below:  1: <h2>Shopping Cart</h2> 2:   3: <% using(Html.BeginForm()) { %> 4: 5: <h3>Products</h3> 6: <% for (int i = 0; i < Model.Products.Count; i++) 7: { %> 8: <div style="width: 100px;float:left;">Id</div> 9: <div style="width: 100px;float:left;"> 10: <%= Html.TextBox("ID", Model.Products[i].Id) %> 11: </div> 12: <div style="clear:both;"></div> 13: <div style="width: 100px;float:left;">Name</div> 14: <div style="width: 100px;float:left;"> 15: <%= Html.TextBox("Name", Model.Products[i].Name) %> 16: </div> 17: <div style="clear:both;"></div> 18: <div style="width: 100px;float:left;">Quantity</div> 19: <div style="width: 100px;float:left;"> 20: <%= Html.TextBox("Quantity", Model.Products[i].Quantity)%> 21: </div> 22: <div style="clear:both;"></div> 23: <div style="width: 100px;float:left;">Unit Price</div> 24: <div style="width: 100px;float:left;"> 25: <%= Html.TextBox("UnitPrice", Model.Products[i].UnitPrice)%> 26: </div> 27: <div style="clear:both;"><hr /></div> 28: <% } %> 29: 30: <h3>Totals</h3> 31: <div style="width: 100px;float:left;">Sub Total</div> 32: <div style="width: 100px;float:left;"> 33: <%= Html.TextBox("SubTotal", Model.Totals.SubTotal)%> 34: </div> 35: <div style="clear:both;"></div> 36: <div style="width: 100px;float:left;">Tax</div> 37: <div style="width: 100px;float:left;"> 38: <%= Html.TextBox("Tax", Model.Totals.Tax)%> 39: </div> 40: <div style="clear:both;"></div> 41: <div style="width: 100px;float:left;">Total</div> 42: <div style="width: 100px;float:left;"> 43: <%= Html.TextBox("Total", Model.Totals.Total)%> 44: </div> 45: <div style="clear:both;"></div> 46: <p /> 47: <input type="submit" name="Submit" value="Submit" /> 48: <% } %> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Nothing fancy, just a bunch of div’s containing textboxes and a submit button. Just make note that the textboxes have the same name as the property they are going to display. Yea, yea, I know. I’m displaying unit price as a textbox instead of a label, but that’s beside the point (and trust me, this will not be how it’ll look on the production site!!). The way my controller works is that initially two dummy products are added to the basked object and the Totals are calculated based on what products were added in what quantities and their respective unit price. So when the page loads in edit mode, where the user can change the quantity and hit the submit button. In the ‘post’ version of the action method, the Totals get recalculated and the new total will be displayed on the screen. Here’s the code: 1: public ActionResult Index() 2: { 3: Product product1 = new Product 4: { 5: Id = 1, 6: Name = "Product 1", 7: Quantity = 2, 8: UnitPrice = 200m 9: }; 10:   11: Product product2 = new Product 12: { 13: Id = 2, 14: Name = "Product 2", 15: Quantity = 1, 16: UnitPrice = 150m 17: }; 18:   19: List<Product> products = new List<Product> { product1, product2 }; 20:   21: Basket basket = new Basket 22: { 23: Products = products, 24: Totals = ComputeTotals(products) 25: }; 26: return View(basket); 27: } 28:   29: [HttpPost] 30: public ActionResult Index(Basket basket) 31: { 32: basket.Totals = ComputeTotals(basket.Products); 33: return View(basket); 34: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } That’s that. Now I run the app, I see two products with the totals section below them. I look at the view source and I see that the input controls have the right ID, the right name and the right value as well. 1: <input id="ID" name="ID" type="text" value="1" /> 2: <input id="Name" name="Name" type="text" value="Product 1" /> 3: ... 4: <input id="ID" name="ID" type="text" value="2" /> 5: <input id="Name" name="Name" type="text" value="Product 2" /> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } So just as a regular user would do, I change the quantity value of one of the products and hit the submit button. The ‘post’ version of the Index method gets called and I had put a break-point on line 32 in the above snippet. When I hovered my mouse on the ‘basked’ object, happily assuming that the object would be all bound and ready for use, I was surprised to see both basket.Products and basket.Totals were null. Huh? A little research and I found out that the reason the DefaultModelBinder could not do its job is because of a naming mismatch on the input controls. What I mean is that when you have to bind to a custom .net type, you need more than just the property name. You need to pass a qualified name to the name property of the input control. I modified my view and the emitted code looked as below: 1: <input id="Product_Name" name="Product.Name" type="text" value="Product 1" /> 2: ... 3: <input id="Product_Name" name="Product.Name" type="text" value="Product 2" /> 4: ... 5: <input id="Totals_SubTotal" name="Totals.SubTotal" type="text" value="550" /> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now, I update the quantity and hit the submit button and I see that the Totals object is populated, but the Products list is still null. Once again I went: ‘Hmm.. time for more research’. I found out that the way to do this is to provide the name as: 1: <%= Html.TextBox(string.Format("Products[{0}].ID", i), Model.Products[i].Id) %> 2: <!-- this will be rendered as --> 3: <input id="Products_0__ID" name="Products[0].ID" type="text" value="1" /> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } It was only now that I was able to see both the products and the totals being properly bound in the ‘post’ action method. Somehow, I feel this is kinda ‘clunky’ way of doing things. Seems like people at MS felt in a similar way and offered us a much cleaner way to solve this issue. The simple solution is that instead of using a Textbox, we can either use a TextboxFor or an EditorFor helper method. This one directly spits out the name of the input property as ‘Products[0].ID and so on. Cool right? I totally fell for this and changed my UI to contain EditorFor helper method. At this point, I ran the application, changed the quantity field and pressed the submit button. Of course my basket object parameter in my action method was correctly bound after these changes. I let the app complete the rest of the lines in the action method. When the page finally rendered, I did see that the quantity was changed to what I entered before the post. But, wait a minute, the totals section did not reflect the changes and showed the old values. My status: COMPLETELY PUZZLED! Just to recap, this is what my ‘post’ Index method looked like: 1: [HttpPost] 2: public ActionResult Index(Basket basket) 3: { 4: basket.Totals = ComputeTotals(basket.Products); 5: return View(basket); 6: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } A careful debug confirmed that the basked.Products[0].Quantity showed the updated value and the ComputeTotals() method also returns the correct totals. But still when I passed this basket object, it ended up showing the old totals values only. I began playing a bit with the code and my first guess was that the input controls got their values from the ModelState object. For those who don’t know, the ModelState is a temporary storage area that ASP.NET MVC uses to retain incoming attempted values plus binding and validation errors. Also, the fact that input controls populate the values using data taken from: Previously attempted values recorded in the ModelState["name"].Value.AttemptedValue Explicitly provided value (<%= Html.TextBox("name", "Some value") %>) ViewData, by calling ViewData.Eval("name") FYI: ViewData dictionary takes precedence over ViewData's Model properties – read more here. These two indicators led to my guess. It took me quite some time, but finally I hit this post where Brad brilliantly explains why this is the preferred behavior. My guess was right and I, accordingly modified my code to reflect the following way: 1: [HttpPost] 2: public ActionResult Index(Basket basket) 3: { 4: // read the following posts to see why the ModelState 5: // needs to be cleared before passing it the view 6: // http://forums.asp.net/t/1535846.aspx 7: // http://forums.asp.net/p/1527149/3687407.aspx 8: if (ModelState.IsValid) 9: { 10: ModelState.Clear(); 11: } 12:   13: basket.Totals = ComputeTotals(basket.Products); 14: return View(basket); 15: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } What this does is that in the case where your ModelState IS valid, it clears the dictionary. This enables the values to be read from the model directly and not from the ModelState. So the verdict is this: If you need to pass other parameters (like html attributes and the like) to your input control, use 1: <%= Html.TextBox(string.Format("Products[{0}].ID", i), Model.Products[i].Id) %> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Since, in EditorFor, there is no direct and simple way of passing this information to the input control. If you don’t have to pass any such ‘extra’ piece of information to the control, then go the EditorFor way. The code used in the post can be found here.

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• CQRS - Benefits

  - by Dylan Smith

  Thanks to all the comments and feedback from the last post I think I have a better understanding now of the benefits of CQRS (separate from the benefits of Event Sourcing). I’m going to try and sum it up here, and point out some areas where I could still use some advice: CQRS Benefits Sounds like the primary benefit of CQRS as an architecture is it allows you to create a simpler domain model by sucking out everything related to queries. I can definitely see the benefit to this, in general the domain logic related to commands is the high-value behavior in the software, but the logic required to service the queries would add a lot of low-value “noise” to the domain model that would dilute the high-value (command) behavior – sorting, paging, filtering, pre-fetch paths, etc. Also the most appropriate domain structure for implementing commands might not be the most optimal for implementing queries. To paraphrase Greg, this usually results in a domain model that is mediocre at both, piss-poor at one, or more likely piss-poor at both commands and queries. Not only will you be able to simplify your domain model by pulling out all the query logic, but at least a handful of commands in most systems will probably be “pass-though” type commands with little to no logic that just generate events. If these can be implemented directly in the command-handler and never touch the domain model, this allows you to slim down the domain model even more. Also, if you were to do event sourcing without CQRS, you no longer have a database containing the current state (only the domain model would) which makes it difficult (or impossible) to support ad-hoc querying and/or reporting that is common in most business software. Of course CQRS provides some great scalability benefits, not only scalability but I have to assume that it provides extremely low latency for most operations, especially if you have an asynchronous event bus. I know Greg says that you get a 3x scaling (Commands, Queries, Client) of your ability to perform parallel development, but IMHO, it seems like it only provides 1.5x scaling since even without CQRS you’re going to have your client loosely coupled to your domain - which is still a great benefit to be able to realize. Questions / Concerns If all the queries against an aggregate get pulled out to the Query layer, what if the only commands for that aggregate can be handled in a “pass-through” manner with the command handler directly generating events. Is it possible to have an aggregate that isn’t modeled in the domain model? Are there any issues or downsides to this? I know in the feedback from my previous posts it was suggested that having one domain model handling both commands and queries requires implementing a lot of traversals between objects that wouldn’t be necessary if it was only servicing commands. My question is, do you include traversals in your domain model based on the needs of the code, or based on the conceptual domain model? If none of my Commands require a Customer.Orders traversal, but the conceptual domain includes the concept of a set of orders belonging to a customer – should I model that in my domain model or not? I like the idea of using the Query side of the architecture as a place to put junior devs where the risk of them screwing something up has minimal impact. But I’m not sold on the idea that you can actually outsource it. Like I said in one of my comments on my previous post, the code to handle a query and generate DTO’s is going to be dead simple, but the code to process events and apply them to the tables on the query side is going to require a significant amount of domain knowledge to know which events to listen for to update each of the de-normalized tables (and what changes need to be made when each event is processed). I don’t know about everybody else, but having Indian/Russian/whatever outsourced developers have to do anything that requires significant domain knowledge has never been successful in my experience. And if you need to spec out for each new query which events to listen to and what to do with each one, well that’s probably going to be just as much work to document as it would be to just implement it. Greg made the point in a comment that doing an aggregate query like “Total Sales By Customer” is going to be inefficient if you use event sourcing but not CQRS. I don’t understand why that would be the case. I imagine in that case you’d simply have a method/property on the Customer object that calculated total sales for that customer by enumerating over the Orders collection. Then the application services layer would generate DTO’s off of the Customers collection that included say the CustomerID, CustomerName, TotalSales, or whatever the case may be. As long as you use a snapshotting implementation, I don’t see why that would be anymore inefficient in a DDD+Event Sourcing implementation than in a typical DDD implementation. Like I mentioned in my last post I still have some questions about query logic that haven’t been answered yet, but before I start asking those I want to make sure I have a strong grasp on what benefits CQRS provides.  My main concern with the query logic was that I know I could just toss it all into the query side, but I was concerned that I would be losing the benefits of using CQRS in the first place if I did that.  I want to elaborate more on this though with some example situations in an upcoming post.

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• Mixing Objective-C and C++: Game Loop Parts

  - by Peteyslatts

  I'm trying to write all of my game in C++ except for drawing and game loop timing. Those parts are going to be in Objective-C for iOS. Right now, I have ViewController handling the update cycle, but I want to create a GameModel class that ViewController could update. I want GameModel to be in C++. I know how to integrate these two classes. My problem is how to have these two parts interact with the drawing and image loading. GameModel will keep track of a list of children of type GameObject. These GameObjects update every frame, and then need to pass position and visibility data to whatever class or method will handle drawing. I feel like I'm answering my own question now (talking it out helps) but would it be a good idea to put all of the visible game objects into an array at the end of the update method, return it, and use that to update graphics inside ViewController?

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• SQL In The City Charlotte - Fundamentals of Database Design

  - by drsql

  Next Monday, October 14, at Red-Gate's SQL In The City conference in Charlotte, NC (one day before PASS), I will be presenting my Fundamentals of Database Design session. It is my big-time chestnut session, the one that I do the most and have the most fun with. This will be the "single" version of the session, weighing in at just under an hour, and it is a lot of material to go over (even with no code samples to go awry to take up time.)  In this hour long session (presented in widescreen...(read more)

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• Google Developers SXSW LEGO Rumble

  Google Developers SXSW LEGO Rumble The Google Developers LEGO® MINDSTORMS® rumble returns to SXSW this year with even more epic proportions. After teams spend the day building LEGO race bots controlled by Android, the bots will compete in the ultimate showdown to determine the victors. We'll be broadcasting live the main event with multiple camera angles, slow-mo replay, interviews with the teams, and commentary from judges and attendees to give you an insider pass to all the action. You won't want to miss this showdown. More information can be found at: www.google.com From: GoogleDevelopers Views: 11238 182 ratings Time: 01:37:01 More in Entertainment

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• How can I write only to the stencil buffer in OpenGL ES 2.0?

  - by stephelton

  I'd like to write to the stencil buffer without incurring the cost of my expensive shaders. As I understand it, I write to the stencil buffer as a 'side effect' of rendering something. In this first pass where I write to the stencil buffer, I don't want to write anything to the color or depth buffer, and I definitely don't want to run through my lighting equations in my shaders. Do I need to create no-op shaders for this (and can I just discard fragments), or is there a better way to do this? As the title says, I'm using OpenGL ES 2.0. I haven't used the stencil buffer before, so if I seem to be misunderstanding something, feel free to be verbose.

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• XNA Notes 005

  - by George Clingerman

  Another week and another crazy amount of activity going on in the XNA community. I’m fairly certain I missed over half of it. In fact, if I am missing things, make sure to email me and I’ll try and make sure I catch it next week! ([email protected]). Also, if you’ve got any advice, things you like/don’t like about the way these XNA Notes are going let me know. I always appreciate feedback (currently spammers are leaving me the nicest comments so you guys have work to do!) Without further ado, here’s this week’s notes! Time Critical XNA News The XNA Team Blob reminds us that February 7th is the last day to submit XNA 3.1 games to peer review! http://blogs.msdn.com/b/xna/archive/2011/01/31/7-days-left-to-submit-xna-gs-3-1-games-on-app-hub.aspx XNA MVPS Chris Williams kicks off the marketing campaign for our book http://geekswithblogs.net/cwilliams/archive/2011/01/28/143680.aspx Catalin Zima posts the comparison cheat sheet for why Angry Birds is different than Chickens Can’t Fly http://www.amusedsloth.com/2011/02/comparison-cheat-sheet-for-chickens-cant-fly-and-angry-birds/ Jim Perry congratulates the developers selected by Game Developer Magazine for Best Xbox LIVE Indie Games of 2010 http://machxgames.com/blog/?p=24 @NemoKrad posts his XNAKUUG talks for all to enjoy http://twitter.com/NemoKrad/statuses/33142362502864896 http://xna-uk.net/blogs/randomchaos/archive/2011/02/03/xblig-uk-2011-january-amp-february-talk.aspx George  (that’s me!) preps for his XNA talk coming up on the 8th http://twitter.com/clingermangw/statuses/32669550554124288 http://www.portlandsilverlight.net/Meetings/Details/15 XNA Developers FireFly posts the last tutorial in his XNA Tower Defense tutorial series http://forums.create.msdn.com/forums/p/26442/451460.aspx#451460 http://xnatd.blogspot.com/2011/01/tutorial-14-polishing-game.html @fredericmy posts the main difference when porting a game from Windows Phone 7 to Xbox 360 http://fairyengine.blogspot.com/2011/01/main-differences-when-porting-game-from.html @ElementCy creates a pretty rad video of a MineCraft type terrain created using XNA http://www.youtube.com/watch?v=Waw1f7wnl9I Andrew Russel gets the first XNA badge on gamedev.stackexchange http://twitter.com/_AndrewRussell/statuses/32322877004972032 http://gamedev.stackexchange.com/badges?tab=tags And his funding for ExEn has passed $7000 only $3000 to go http://twitter.com/_AndrewRussell/statuses/33042412804771840 Subodh Pushpak blogs about his Windows Phone 7 XNA talk http://geekswithblogs.net/subodhnpushpak/archive/2011/02/01/windows-phone-7-silverlight--xna-development-talk.aspx Slyprid releases the latest version of Transmute and needs more people to test http://twitter.com/slyprid/statuses/32452488418299904 http://forgottenstarstudios.com/ SpynDoctorGames celebrates the 1 year anniversary of Your Doodles Are Bugged! Congrats! http://twitter.com/SpynDoctorGames/statuses/32511689068908544 Noogy (creator of Dust the Elysian Tail) prepares his conversion to XNA 4.0 http://twitter.com/NoogyTweet/statuses/32522008449253376 @philippedasilva posts about the Indiefreaks Game Framework v0.2.0.0 Input management system http://twitter.com/philippedasilva/statuses/32763393957957632 http://indiefreaks.com/2011/02/02/behind-smart-input-system-feature/ Mommy’s Best Games debates what to do about High Scores with their new update http://mommysbest.blogspot.com/2011/02/high-score-shake-up.html @BinaryTweedDeej want to know if there’s anything the community needs to make XNA games for the PC. Give him some feedback! http://twitter.com/BinaryTweedDeej/status/32895453863354368 @mikebmcl promises to write us all a book (I can’t wait to read it!) http://twitter.com/mikebmcl/statuses/33206499102687233 @werezompire is going to live, LIVE, thanks to all the generosity and support from the community! http://twitter.com/werezompire/statuses/32840147644977153 Xbox LIVE Indie Games (XBLIG) Making money in Xbox 360 indie game development. Is it possible? http://www.bitmob.com/articles/making-money-in-xbox-360-indie-game-development-is-it-possible @AlejandroDaJ posts some thoughts abut the bitmob article http://twitter.com/AlejandroDaJ/statuses/31068552165330944 http://www.apathyworks.com/blog/view.php?id=00215 Kobun gets my respect as an XBLIG champion. I’m not sure who Kobun is, but if you’ve every read through the comment sections any time Kotaku writes about XBLIGs you’ll see a lot of confusion, disinformation in there. Kobun has been waging a secret war battling that lack of knowledge and he does it well. Also he’s running a pretty kick ass site for Xbox LIVE Indie Game reviews http://xboxindies.teamkobun.com/ @radiangames releases his last Xbox LIVE Indie Game...for now http://bit.ly/gMK6lE Playing Avaglide with the Kinect controller http://www.youtube.com/watch?v=UqAYbHww53o http://www.joystiq.com/2011/01/30/kinect-hacks-take-to-the-skies-with-avaglide/ Luke Schneider of Radiangames interviewed in Edge magazine http://www.next-gen.biz/features/radiangames-venture Digital Quarters posts thoughts on why XBLIG’s online requirement kills certain genres http://digitalquarters.blogspot.com/2011/02/thoughts-why-xbligs-online-requirement.html Mommy’s Best Games shares the news that several XBLIGs were featured in the March 2011 issue of Famitsu 360 http://forums.create.msdn.com/forums/p/33455/451487.aspx#451487 NaviFairy continues with his Indie-Game-A-Day http://gaygamer.net/2011/02/indie_game_a_day_epic_dungeon.html http://gaygamer.net/2011/02/indie_game_a_day_break_limit_r.html and more every day...that’s kind of the point! Keep your eye on this series! VVGTV continues with it’s awesome reviews/promotions for XBLIGs http://vvgtv.com/ http://vvgtv.com/2011/02/03/iredia-atrams-secret-xblig-review-2/ http://vvgtv.com/2011/02/02/poopocalypse-coming-soon-to-xblig/ ….and even more, you get the point. Magicka is an Indie Game doing really well on Steam AND it’s made using XNA http://www.magickagame.com/ http://twitter.com/Magickagame/statuses/32712762580799488 GameMarx reviews Antipole http://www.gamemarx.com/reviews/73/antipole-is-vvvvvvery-good.aspx Armless Octopus review Alpha Squad http://www.armlessoctopus.com/2011/01/28/xbox-indie-review-alpha-squad/ An interesting article about Kodu that Jim Perry found http://twitter.com/MachXGames/statuses/32848044105924608 http://www.develop-online.net/news/36915/10-year-old-Jordan-makes-games-The-UK-needs-more-like-her XNA Game Development Sgt. Conker posts about the Natur beta, a new book and whether you can make money with XBLIG http://www.sgtconker.com/ http://www.sgtconker.com/2011/01/a-new-book-on-the-block-and-a-new-natur-beta/ http://www.sgtconker.com/2011/01/making-money-in-xbox-360-indie-game-development-is-it-possible/ Tips for setting up SVN http://bit.ly/fKxgFh @bsimser found tons of royalty free music and soundfx for your XNA Games http://twitter.com/bsimser/statuses/31426632933711872 Post on the new features in the next Sunburn Editor http://www.synapsegaming.com/blogs/fivesidedbarrel/archive/2011/01/28/new-editor-features-prefabs-components-and-more.aspx @jasons_novaleaf posts source code for light pre-pass optimizations for #xna http://twitter.com/jasons_novaleaf/statuses/33348855403642880 http://jcoluna.wordpress.com/2011/02/01/xna-4-0-light-pre-pass-optimization-round-one/ I’ve been learning about doing an A.I. for turn based games and this article was a great resource. http://www.gamasutra.com/view/feature/1535/designing_ai_algorithms_for_.php?print=1

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• Best way to throw exception and avoid code duplication

  - by JF Dion

  I am currently writing code and want to make sure all the params that get passed to a function/method are valid. Since I am writing in PHP I don't have access to all the facilities of other languages like C, C++ or Java to check for parameters values and types public function inscriptionExists($sectionId, $userId) // PHP vs. public boolean inscriptionExists(int sectionId, int userId) // Java So I have to rely on exceptions if I want to make sure that my params are both integers. Since I have a lot of places where I need to check for param validity, what would be the best way to create a validation/exception machine and avoid code duplication? I was thinking on a static factory (since I don't want to pass it to all of my classes) with a signature like: public static function factory ($value, $valueType, $exceptionType = 'InvalidArgumentException'); Which would then call the right sub process to validate based on the type. Am I on the right way, or am I going completely off the road and overthinking my problem?

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• Liskov Substitution Principle and the Oft Forgot Third Wheel

  - by Stacy Vicknair

  Liskov Substitution Principle (LSP) is a principle of object oriented programming that many might be familiar with from the SOLID principles mnemonic from Uncle Bob Martin. The principle highlights the relationship between a type and its subtypes, and, according to Wikipedia, is defined by Barbara Liskov and Jeanette Wing as the following principle:   Let be a property provable about objects of type . Then should be provable for objects of type where is a subtype of .   Rectangles gonna rectangulate The iconic example of this principle is illustrated with the relationship between a rectangle and a square. Let’s say we have a class named Rectangle that had a property to set width and a property to set its height. 1: Public Class Rectangle 2: Overridable Property Width As Integer 3: Overridable Property Height As Integer 4: End Class   We all at some point here that inheritance mocks an “IS A” relationship, and by gosh we all know square IS A rectangle. So let’s make a square class that inherits from rectangle. However, squares do maintain the same length on every side, so let’s override and add that behavior. 1: Public Class Square 2: Inherits Rectangle 3:  4: Private _sideLength As Integer 5:  6: Public Overrides Property Width As Integer 7: Get 8: Return _sideLength 9: End Get 10: Set(value As Integer) 11: _sideLength = value 12: End Set 13: End Property 14:  15: Public Overrides Property Height As Integer 16: Get 17: Return _sideLength 18: End Get 19: Set(value As Integer) 20: _sideLength = value 21: End Set 22: End Property 23: End Class   Now, say we had the following test: 1: Public Sub SetHeight_DoesNotAffectWidth(rectangle As Rectangle) 2: 'arrange 3: Dim expectedWidth = 4 4: rectangle.Width = 4 5:  6: 'act 7: rectangle.Height = 7 8:  9: 'assert 10: Assert.AreEqual(expectedWidth, rectangle.Width) 11: End Sub   If we pass in a rectangle, this test passes just fine. What if we pass in a square?   This is where we see the violation of Liskov’s Principle! A square might "IS A” to a rectangle, but we have differing expectations on how a rectangle should function than how a square should! Great expectations Here’s where we pat ourselves on the back and take a victory lap around the office and tell everyone about how we understand LSP like a boss. And all is good… until we start trying to apply it to our work. If I can’t even change functionality on a simple setter without breaking the expectations on a parent class, what can I do with subtyping? Did Liskov just tell me to never touch subtyping again? The short answer: NO, SHE DIDN’T. When I first learned LSP, and from those I’ve talked with as well, I overlooked a very important but not appropriately stressed quality of the principle: our expectations. Our inclination is to want a logical catch-all, where we can easily apply this principle and wipe our hands, drop the mic and exit stage left. That’s not the case because in every different programming scenario, our expectations of the parent class or type will be different. We have to set reasonable expectations on the behaviors that we expect out of the parent, then make sure that those expectations are met by the child. Any expectations not explicitly expected of the parent aren’t expected of the child either, and don’t register as a violation of LSP that prevents implementation. You can see the flexibility mentioned in the Wikipedia article itself: A typical example that violates LSP is a Square class that derives from a Rectangle class, assuming getter and setter methods exist for both width and height. The Square class always assumes that the width is equal with the height. If a Square object is used in a context where a Rectangle is expected, unexpected behavior may occur because the dimensions of a Square cannot (or rather should not) be modified independently. This problem cannot be easily fixed: if we can modify the setter methods in the Square class so that they preserve the Square invariant (i.e., keep the dimensions equal), then these methods will weaken (violate) the postconditions for the Rectangle setters, which state that dimensions can be modified independently. Violations of LSP, like this one, may or may not be a problem in practice, depending on the postconditions or invariants that are actually expected by the code that uses classes violating LSP. Mutability is a key issue here. If Square and Rectangle had only getter methods (i.e., they were immutable objects), then no violation of LSP could occur. What this means is that the above situation with a rectangle and a square can be acceptable if we do not have the expectation for width to leave height unaffected, or vice-versa, in our application. Conclusion – the oft forgot third wheel Liskov Substitution Principle is meant to act as a guidance and warn us against unexpected behaviors. Objects can be stateful and as a result we can end up with unexpected situations if we don’t code carefully. Specifically when subclassing, make sure that the subclass meets the expectations held to its parent. Don’t let LSP think you cannot deviate from the behaviors of the parent, but understand that LSP is meant to highlight the importance of not only the parent and the child class, but also of the expectations WE set for the parent class and the necessity of meeting those expectations in order to help prevent sticky situations.   Code examples, in both VB and C# Technorati Tags: LSV,Liskov Substitution Principle,Uncle Bob,Robert Martin,Barbara Liskov,Liskov

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• how to re-use a sprite in cocos2d-x

  - by zinking

  some times it takes time to create the sprite structures in the scene, I might need to setup structures inside this sprite to meet requirement, thus I would hope to reuse such structures with the game again and again. I tried that, remove the child from parent, detach it from parent , clean parent with the sprite. but when I try to add the sprite to another scene, it's just wont pass the assertion that the sprite already have parent did I miss some step ? add an example: I have a sprite A which involves of quite a few steps to construct, so I used it in scene A layer A, and then I want to use it in scene A layer B, scene B layer A1 etc..... generally speaking I don't want to reconstruct the sprte again.

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• How to perform regular expression based replacements on files with MSBuild

  - by Daniel Cazzulino

  And without a custom DLL with a task, too . The example at the bottom of the MSDN page on MSBuild Inline Tasks already provides pretty much all you need for that with a TokenReplace task that receives a file path, a token and a replacement and uses string.Replace with that. Similar in spirit but way more useful in its implementation is the RegexTransform in NuGet’s Build.tasks. It’s much better not only because it supports full regular expressions, but also because it receives items, which makes it very amenable to batching (applying the transforms to multiple items). You can read about how to use it for updating assemblies with a version number, for example. I recently had a need to also supply RegexOptions to the task so I extended the metadata and a little bit of the inline task so that it can parse the optional flags. So when using the task, I can pass the flags as item metadata as follows:...Read full article

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• Call for Papers Ends March 21

  - by jack.flynn

  Have Something to Say? Better Say So Now. The Call for Papers for Oracle OpenWorld and the Develop Stream of JavaOne+Develop ends at midnight on Sunday, March 21. So if you want to be a part of the most influential IT events of the year, don't let this chance pass you by. This year offers opportunities to speak out about some new subjects: Oracle OpenWorld adds a whole new Server and Storage Systems stream, including Sun servers, Sun storage and tape, and Oracle Solaris operating system. And the Develop audience should be larger and more energetic than ever now that it's co-located with JavaOne. If you have something important to say, this is the time to let us know. Find all the information on the Call for Papers process, timeline, and guidelines here.

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• TechDays 2010: What’s New On C# 4.0

  - by Paulo Morgado

  I would like to thank those that attended my session at TechDays 2010 and I hope that I was able to pass the message of what’s new on C#. For those that didn’t attend (or did and want to review it), the presentation can be downloaded from here. Code samples can be downlaoded from here. Here’s a list of resources mentioned on the session: The evolution of C# The Evolution Of C# Covariance and contravariance  C# 4.0: Covariance And Contravariance In Generics Covariance And Contravariance In Generics Made Easy Covarince and Contravariance in Generics Exact rules for variance validity Events get a little overhaul in C# 4, Afterward: Effective Events Named and optional arguments  Named And Optional Arguments Alternative To Optional Arguments Named and Optional Arguments (C# Programming Guide) Dynamic programming  Dynamic Programming C# Proposal: Compile Time Static Checking Of Dynamic Objects Using Type dynamic (C# Programming Guide) Dynamic Language Runtime Overview COM Interop Improvements COM Interop Improvements Type Equivalence and Embedded Interop Types Conclusion Visual C# Developer Center Visual C# 2010 Samples C# Language Specification 4.0 .NET Reflector LINQPad

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• shader coding: calculate screen coordinates of fragment

  - by Jay

  Good morning, I'm new to shader coding and trying to implement some visual effects code in shaders using billboards. (Yes, I couldn't have picked anything harder to start with, but I'm lucky that way) Setup: I have rendered the full screen z depth to an array of floats in a previous pass. In the fragment shader I need the scene depth where the rendered fragment is displayed (to see if it's occluded). I can use tex2d() to get the depth value if I have the screen coordinates of the point being rendered in the fragment shader. Question: In the fragment shader how do you calculate the screen coordinates of the pixel (in the range 0-1.0)? Is the position passed to the fragment shader a pixel offset? If so, I guess it would be: float2( position.x / screen-width, position.y / screen-height ) Thanks for any help/

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• database api commands

  - by Rahul Mehta

  As I am developing database api for a project. I am developing commands for getting data from database. e.g. i have one gib table so command for that is getgib name alias limit fields if user pass the name e.g. getgib rahul than it will return all the gib data whose name is like rahul. if alias is given than it will return the all the gib owned by the user whose alias(userid) given . So i want to design the commands. limit : is to limit the record in query, fields : is the extra fields i want to add in the select query . so as now commands are set but now Question 1 : i want the gibs by the gibid , so how to make this or any suggestion to improve my command is welcome. Question 2 : if user don't want to specify the name , and he want only the gibs by providing alias then at this what separator at the place of name i should used.

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• Getting to grips with the stack in nasm

  - by MarkPearl

  Today I spent a good part of my day getting to grips with the stack and nasm. After looking at my notes on nasm I think this is one area for the course I am doing they could focus more on… So here are some snippets I have put together that have helped me understand a little bit about the stack… Simplest example of the stack You will probably see examples like the following in circulation… these demonstrate the simplest use of the stack… org 0x100 bits 16 jmp main main: push 42h push 43h push 44h mov ah,2h ;set to display characters pop dx    ;get the first value int 21h   ;and display it pop dx    ;get 2nd value int 21h   ;and display it pop dx    ;get 3rd value int 21h   ;and display it int 20h The output from above code would be… DCB Decoupling code using “call” and “ret” This is great, but it oversimplifies what I want to use the stack for… I do not know if this goes against the grain of assembly programmers or not, but I want to write loosely coupled assembly code – and I want to use the stack as a mechanism for passing values into my decoupled code. In nasm we have the call and return instructions, which provides a mechanism for decoupling code, for example the following could be done… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov ah,2h mov dx,41h int 21h ret ;---------------------------------------- main: call displayChar int 20h   This would output the following to the console A So, it would seem that call and ret allow us to jump to segments of our code and then return back to the calling position – a form of segmenting the code into what we would called in higher order languages “functions” or “methods”. The only issue is, in higher order languages there is a way to pass parameters into the functions and return results. Because of the primitive nature of the call and ret instructions, this does not seem to be obvious. We could of course use the registers to pass values into the subroutine and set values coming out, but the problem with this is we… Have a limited number of registers Are threading our code with tight coupling (it would be hard to migrate methods outside of their intended use in a particular program to another one) With that in mind, I turn to the stack to provide a loosely coupled way of calling subroutines… First attempt with the Stack Initially I thought this would be simple… we could use code that looks as follows to achieve what I want… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov ah,2h pop dx int 21h ret ;---------------------------------------- main: push 41h call displayChar int 20h   However running this application does not give the desired result, I want an ‘A’ to be returned, and I am getting something totally different (you will to). Reading up on the call and ret instructions a discovery is made… they are pushing and popping things onto and off the stack as well… When the call instruction is executed, the current value of IP (the address of the instruction to follow) is pushed onto the stack, when ret is called, the last value on the stack is popped off into the IP register. In effect what the above code is doing is as follows with the stack… push 41h push current value of ip pop current value of ip to dx pop 41h to ip This is not what I want, I need to access the 41h that I pushed onto the stack, but the call value (which is necessary) is putting something in my way. So, what to do? Remember we have other registers we can use as well as a thing called indirect addressing… So, after some reading around, I came up with the following approach using indirect addressing… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov bp,sp mov ah,2h mov dx,[bp+2] int 21h ret ;---------------------------------------- main: push 41h call displayChar int 20h In essence, what I have done here is used a trick with the stack pointer… it goes as follows… Push 41 onto the stack Make the call to the function, which will push the IP register onto the stack and then jump to the displayChar label Move the value in the stack point to the bp register (sp currently points at IP register) Move the at the location of bp minus 2 bytes to dx (this is now the value 41h) display it, execute the ret instruction, which pops the ip value off the stack and goes back to the calling point This approach is still very raw, some further reading around shows that I should be pushing the value of bp onto the stack before replacing it with sp, but it is the starting thread to getting loosely coupled subroutines. Let’s see if you get what the following output would be? org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov bp,sp mov ah,2h mov dx,[bp+4] int 21h mov dx,[bp+2] int 21h ret ;---------------------------------------- main: push 41h push 42h call displayChar int 20h The output is… AB Where to from here? If by any luck some assembly programmer comes along and see this code and notices that I have made some fundamental flaw in my logic… I would like to know, so please leave a comment… appreciate any feedback!

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• Entity/Component based engine rendering separation from logic

  - by Denis Narushevich

  I noticed in Unity3D that each gameObject(entity) have its own renderer component, as far I understand, such component handle rendering logic. I wonder if it is a common practice in entity/component based engines, when single entity have renderer components and logic components such as position, behavior altogether in one box? Such approach sound odd to me, in my understanding entity itself belongs to logic part and shouldn't contain any render specific things inside. With such approach it is impossible to swap renderers, it would require to rewrite all that customized renderers. The way I would do it is, that entity would contain only logic specific components, like AI,transform,scripts plus reference to mesh, or sprite. Then some entity with Camera component would store all references to object that is visible to the camera. And in order to render all that stuff I would have to pass Camera reference to Renderer class and render all sprites,meshes of visible entities. Is such approach somehow wrong?

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• Geometry instancing in OpenGL ES 2.0

  - by seahorse

  I am planning to do geometry instancing in OpenGL ES 2.0 Basically I plan to render the same geometry(a chair) maybe 1000 times in my scene. What is the best way to do this in OpenGL ES 2.0? I am considering passing model view mat4 as an attribute. Since attributes are per vertex data do I need to pass this same mat4, three times for each vertex of the same triangle(since modelview remains constant across vertices of the triangle). That would amount to a lot of extra data sent to the GPU( 2 extra vertices*16 floats*(Number of triangles) amount of extra data). Or should I be sending the mat4 only once per triangle?But how is that possible using attributes since attributes are defined as "per vertex" data? What is the best and efficient way to do instancing in OpenGL ES 2.0?

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• Maintaining packages with code - Adding a property expression programmatically

  Every now and then I've come across scenarios where I need to update a lot of packages all in the same way. The usual scenario revolves around a group of packages all having been built off the same package template, and something needs to updated to keep up with new requirements, a new logging standard for example.You'd probably start by updating your template package, but then you need to address all your existing packages. Often this can run into the hundreds of packages and clearly that's not a job anyone wants to do by hand. I normally solve the problem by writing a simple console application that looks for files and patches any package it finds, and it is an example of this I'd thought I'd tidy up a bit and publish here. This sample will look at the package and find any top level Execute SQL Tasks, and change the SQL Statement property to use an expression. It is very simplistic working on top level tasks only, so nothing inside a Sequence Container or Loop will be checked but obviously the code could be extended for this if required. The code that actually sets the expression is shown below, the rest is just wrapper code to find the package and to find the task. /// <summary> /// The CreationName of the Tasks to target, e.g. Execute SQL Task /// </summary> private const string TargetTaskCreationName = "Microsoft.SqlServer.Dts.Tasks.ExecuteSQLTask.ExecuteSQLTask, Microsoft.SqlServer.SQLTask, Version=9.0.242.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91"; /// <summary> /// The name of the task property to target. /// </summary> private const string TargetPropertyName = "SqlStatementSource"; /// <summary> /// The property expression to set. /// </summary> private const string ExpressionToSet = "@[User::SQLQueryVariable]"; .... // Check if the task matches our target task type if (taskHost.CreationName == TargetTaskCreationName) { // Check for the target property if (taskHost.Properties.Contains(TargetPropertyName)) { // Get the property, check for an expression and set expression if not found DtsProperty property = taskHost.Properties[TargetPropertyName]; if (string.IsNullOrEmpty(property.GetExpression(taskHost))) { property.SetExpression(taskHost, ExpressionToSet); changeCount++; } } } This is a console application, so to specify which packages you want to target you have three options: Find all packages in the current folder, the default behaviour if no arguments are specified TaskExpressionPatcher.exe .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Find all packages in a specified folder, pass the folder as the argument TaskExpressionPatcher.exe C:\Projects\Alpha\Packages\ .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Find a specific package, pass the file path as the argument TaskExpressionPatcher.exe C:\Projects\Alpha\Packages\Package.dtsx The code was written against SQL Server 2005, but just change the reference to Microsoft.SQLServer.ManagedDTS to be the SQL Server 2008 version and it will work fine. If you get an error Microsoft.SqlServer.Dts.Runtime.DtsRuntimeException: The package failed to load due to error 0xC0011008… then check that the package is from the correct version of SSIS compared to the referenced assemblies, 2005 vs 2008 in other words. Download Sample Project TaskExpressionPatcher.zip (6 KB)

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• Update/Insert With ADF Web Service Data Control

  - by shay.shmeltzer

  The Web service data control (WSDC) in ADF is a powerful feature that allows you to easily build a UI on top of WS interfaces exposed by other systems. However when you drag a WSDC to a page you usually get a set of output components where the data is shown. So how would you actually do an update operation on those values? The answer is that you need a call to another method in your WSDC that does the update - but what if you want to pass to it the actual values that you get from the get method you invoked before? Here is a demo showing how to do that: The two tricks that are shown here are: Changing the properties of items in the DC to be updateable - this gives you inputText fields instead of outputText fields. And passing the currentRow.dataProvider to the update method (and choosing the right iterator for this).

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• How properly perform passing operation result to View

  - by atomAltera

  I'm developing web site on self made MVC engine. I have actionController that handles operations like register, login, post submit and etc. actionController receives operation name and parameters. Of course it mast handle errors such user with same nick already exists or password is to short about which action handler have to notify user. The question is which is the best way to organize errors, such that View could easily get localized user notification message. I see two ways First one: define error constants like ERR_NICK_BUSY = '1' ERR_NICK_INVALID = '2' ... and localization map local[ERR_NICK_BUSY] = 'User with the same nick already registered' local[ERR_NICK_INVALID ] = 'Nick, you entered is invalid' ... And second one: define abstract constants like ERR_FIELD_BUSY = '1' ERR_FIELD_INVALID = '2' ... and pass them with field name. In this case localization looks like local['nick_'+ERR_FIELD_BUSY] = 'User with the same nick already registered' ... I don't like both this methods. Can you advise something else?

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• Looking for Cutting-Edge Data Integration: 2010 Innovation Awards

  - by dain.hansen

  This year's Oracle Fusion Middleware Innovation Awards will honor customers and partners who are creatively using to various products across Oracle Fusion Middleware. Brand new to this year's awards is a category for Data Integration. Think you have something unique and innovative with one of our Oracle Data Integration products? We'd love to hear from you! Please submit today The deadline for the nomination is 5 p.m. PT Friday, August 6th 2010, and winning organizations will be notified by late August 2010. What you win! FREE pass to Oracle OpenWorld 2010 in San Francisco for select winners in each category. Honored by Oracle executives at awards ceremony held during Oracle OpenWorld 2010 in San Francisco. Oracle Middleware Innovation Award Winner Plaque 1-3 meetings with Oracle Executives during Oracle OpenWorld 2010 Feature article placement in Oracle Magazine and placement in Oracle Press Release Customer snapshot and video testimonial opportunity, to be hosted on oracle.com Podcast interview opportunity with Senior Oracle Executive

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