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  • Auto-hydrate your objects with ADO.NET

    - by Jake Rutherford
    Recently while writing the monotonous code for pulling data out of a DataReader to hydrate some objects in an application I suddenly wondered "is this really necessary?" You've probably asked yourself the same question, and many of you have: - Used a code generator - Used a ORM such as Entity Framework - Wrote the code anyway because you like busy work     In most of the cases I've dealt with when making a call to a stored procedure the column names match up with the properties of the object I am hydrating. Sure that isn't always the case, but most of the time it's 1 to 1 mapping.  Given that fact I whipped up the following method of hydrating my objects without having write all of the code. First I'll show the code, and then explain what it is doing.      /// <summary>     /// Abstract base class for all Shared objects.     /// </summary>     /// <typeparam name="T"></typeparam>     [Serializable, DataContract(Name = "{0}SharedBase")]     public abstract class SharedBase<T> where T : SharedBase<T>     {         private static List<PropertyInfo> cachedProperties;         /// <summary>         /// Hydrates derived class with values from record.         /// </summary>         /// <param name="dataRecord"></param>         /// <param name="instance"></param>         public static void Hydrate(IDataRecord dataRecord, T instance)         {             var instanceType = instance.GetType();                         //Caching properties to avoid repeated calls to GetProperties.             //Noticable performance gains when processing same types repeatedly.             if (cachedProperties == null)             {                 cachedProperties = instanceType.GetProperties().ToList();             }                         foreach (var property in cachedProperties)             {                 if (!dataRecord.ColumnExists(property.Name)) continue;                 var ordinal = dataRecord.GetOrdinal(property.Name);                 var isNullable = property.PropertyType.IsGenericType &&                                  property.PropertyType.GetGenericTypeDefinition() == typeof (Nullable<>);                 var isNull = dataRecord.IsDBNull(ordinal);                 var propertyType = property.PropertyType;                 if (isNullable)                 {                     if (!string.IsNullOrEmpty(propertyType.FullName))                     {                         var nullableType = Type.GetType(propertyType.FullName);                         propertyType = nullableType != null ? nullableType.GetGenericArguments()[0] : propertyType;                     }                 }                 switch (Type.GetTypeCode(propertyType))                 {                     case TypeCode.Int32:                         property.SetValue(instance,                                           (isNullable && isNull) ? (int?) null : dataRecord.GetInt32(ordinal), null);                         break;                     case TypeCode.Double:                         property.SetValue(instance,                                           (isNullable && isNull) ? (double?) null : dataRecord.GetDouble(ordinal),                                           null);                         break;                     case TypeCode.Boolean:                         property.SetValue(instance,                                           (isNullable && isNull) ? (bool?) null : dataRecord.GetBoolean(ordinal),                                           null);                         break;                     case TypeCode.String:                         property.SetValue(instance, (isNullable && isNull) ? null : isNull ? null : dataRecord.GetString(ordinal),                                           null);                         break;                     case TypeCode.Int16:                         property.SetValue(instance,                                           (isNullable && isNull) ? (int?) null : dataRecord.GetInt16(ordinal), null);                         break;                     case TypeCode.DateTime:                         property.SetValue(instance,                                           (isNullable && isNull)                                               ? (DateTime?) null                                               : dataRecord.GetDateTime(ordinal), null);                         break;                 }             }         }     }   Here is a class which utilizes the above: [Serializable] [DataContract] public class foo : SharedBase<foo> {     [DataMember]     public int? ID { get; set; }     [DataMember]     public string Name { get; set; }     [DataMember]     public string Description { get; set; }     [DataMember]     public string Subject { get; set; }     [DataMember]     public string Body { get; set; }            public foo(IDataRecord record)     {         Hydrate(record, this);                }     public foo() {} }   Explanation: - Class foo inherits from SharedBase specifying itself as the type. (NOTE SharedBase is abstract here in the event we want to provide additional methods which could be overridden by the instance class) public class foo : SharedBase<foo> - One of the foo class constructors accepts a data record which then calls the Hydrate method on SharedBase passing in the record and itself. public foo(IDataRecord record) {      Hydrate(record, this); } - Hydrate method on SharedBase will use reflection on the object passed in to determine its properties. At the same time, it will effectively cache these properties to avoid repeated expensive reflection calls public static void Hydrate(IDataRecord dataRecord, T instance) {      var instanceType = instance.GetType();      //Caching properties to avoid repeated calls to GetProperties.      //Noticable performance gains when processing same types repeatedly.      if (cachedProperties == null)      {           cachedProperties = instanceType.GetProperties().ToList();      } . . . - Hydrate method on SharedBase will iterate each property on the object and determine if a column with matching name exists in data record foreach (var property in cachedProperties) {      if (!dataRecord.ColumnExists(property.Name)) continue;      var ordinal = dataRecord.GetOrdinal(property.Name); . . . NOTE: ColumnExists is an extension method I put on IDataRecord which I’ll include at the end of this post. - Hydrate method will determine if the property is nullable and whether the value in the corresponding column of the data record has a null value var isNullable = property.PropertyType.IsGenericType && property.PropertyType.GetGenericTypeDefinition() == typeof (Nullable<>); var isNull = dataRecord.IsDBNull(ordinal); var propertyType = property.PropertyType; . . .  - If Hydrate method determines the property is nullable it will determine the underlying type and set propertyType accordingly - Hydrate method will set the value of the property based upon the propertyType   That’s it!!!   The magic here is in a few places. First, you may have noticed the following: public abstract class SharedBase<T> where T : SharedBase<T> This says that SharedBase can be created with any type and that for each type it will have it’s own instance. This is important because of the static members within SharedBase. We want this behavior because we are caching the properties for each type. If we did not handle things in this way only 1 type could be cached at a time, or, we’d need to create a collection that allows us to cache the properties for each type = not very elegant.   Second, in the constructor for foo you may have noticed this (literally): public foo(IDataRecord record) {      Hydrate(record, this); } I wanted the code for auto-hydrating to be as simple as possible. At first I wasn’t quite sure how I could call Hydrate on SharedBase within an instance of the class and pass in the instance itself. Fortunately simply passing in “this” does the trick. I wasn’t sure it would work until I tried it out, and fortunately it did.   So, to actually use this feature when utilizing ADO.NET you’d do something like the following:        public List<foo> GetFoo(int? fooId)         {             List<foo> fooList;             const string uspName = "usp_GetFoo";             using (var conn = new SqlConnection(_dbConnection))             using (var cmd = new SqlCommand(uspName, conn))             {                 cmd.CommandType = CommandType.StoredProcedure;                 cmd.Parameters.Add(new SqlParameter("@FooID", SqlDbType.Int)                                        {Direction = ParameterDirection.Input, Value = fooId});                 conn.Open();                 using (var dr = cmd.ExecuteReader())                 {                     fooList= (from row in dr.Cast<DbDataRecord>()                                             select                                                 new foo(row)                                            ).ToList();                 }             }             return fooList;         }   Nice! Instead of having line after line manually assigning values from data record to an object you simply create a new instance and pass in the data record. Note that there are certainly instances where columns returned from stored procedure do not always match up with property names. In this scenario you can still use the above method and simply do your manual assignments afterward.

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  • Using LINQ to Twitter OAuth with Windows 8

    - by Joe Mayo
    In previous posts, I explained how to use LINQ to Twitter with Windows 8, but the example was a Twitter Search, which didn’t require authentication. Much of the Twitter API requires authentication, so this post will explain how you can perform OAuth authentication with LINQ to Twitter in a Windows 8 Metro-style application. Getting Started I have earlier posts on how to create a Windows 8 app and add pages, so I’ll assume it isn’t necessary to repeat here. One difference is that I’m using Visual Studio 2012 RC and some of the terminology and/or library code might be slightly different.  Here are steps to get started: Create a new Windows metro style app, selecting the Blank App project template. Create a new Basic Page and name it OAuth.xaml.  Note: You’ll receive a prompt window for adding files and you should click Yes because those files are necessary for this demo. Add a new Basic Page named TweetPage.xaml. Open App.xaml.cs and change !rootFrame.Navigate(typeof(MainPage)) to !rootFrame.Navigate(typeof(TweetPage)). Now that the project is set up you’ll see the reason why authentication is required by setting up the TweetPage. Setting Up to Tweet a Status In this section, I’ll show you how to set up the XAML and code-behind for a tweet.  The tweet logic will check to see if the user is authenticated before performing the tweet. To tweet, I put a TextBox and Button on the XAML page. The following code omits most of the page, concentrating primarily on the elements of interest in this post: <StackPanel Grid.Row="1"> <TextBox Name="TweetTextBox" Margin="15" /> <Button Name="TweetButton" Content="Tweet" Click="TweetButton_Click" Margin="15,0" /> </StackPanel> Given the UI above, the user types the message they want to tweet, and taps Tweet. This invokes TweetButton_Click, which checks to see if the user is authenticated.  If the user is not authenticated, the app navigates to the OAuth page.  If they are authenticated, LINQ to Twitter does an UpdateStatus to post the user’s tweet.  Here’s the TweetButton_Click implementation: void TweetButton_Click(object sender, RoutedEventArgs e) { PinAuthorizer auth = null; if (SuspensionManager.SessionState.ContainsKey("Authorizer")) { auth = SuspensionManager.SessionState["Authorizer"] as PinAuthorizer; } if (auth == null || !auth.IsAuthorized) { Frame.Navigate(typeof(OAuthPage)); return; } var twitterCtx = new TwitterContext(auth); Status tweet = twitterCtx.UpdateStatus(TweetTextBox.Text); new MessageDialog(tweet.Text, "Successful Tweet").ShowAsync(); } For authentication, this app uses PinAuthorizer, one of several authorizers available in the LINQ to Twitter library. I’ll explain how PinAuthorizer works in the next section. What’s important here is that LINQ to Twitter needs an authorizer to post a Tweet. The code above checks to see if a valid authorizer is available. To do this, it uses the SuspensionManager class, which is part of the code generated earlier when creating OAuthPage.xaml. The SessionState property is a Dictionary<string, object> and I’m using the Authorizer key to store the PinAuthorizer.  If the user previously authorized during this session, the code reads the PinAuthorizer instance from SessionState and assigns it to the auth variable. If the user is authorized, auth would not be null and IsAuthorized would be true. Otherwise, the app navigates the user to OAuthPage.xaml, which I’ll discuss in more depth in the next section. When the user is authorized, the code passes the authorizer, auth, to the TwitterContext constructor. LINQ to Twitter uses the auth instance to build OAuth signatures for each interaction with Twitter.  You no longer need to write any more code to make this happen. The code above accepts the tweet just posted in the Status instance, tweet, and displays a message with the text to confirm success to the user. You can pull the PinAuthorizer instance from SessionState, instantiate your TwitterContext, and use it as you need. Just remember to make sure you have a valid authorizer, like the code above. As shown earlier, the code navigates to OAuthPage.xaml when a valid authorizer isn’t available. The next section shows how to perform the authorization upon arrival at OAuthPage.xaml. Doing the OAuth Dance This section shows how to authenticate with LINQ to Twitter’s built-in OAuth support. From the user perspective, they must be navigated to the Twitter authentication page, add credentials, be navigated to a Pin number page, and then enter that Pin in the Windows 8 application. The following XAML shows the relevant elements that the user will interact with during this process. <StackPanel Grid.Row="2"> <WebView x:Name="OAuthWebBrowser" HorizontalAlignment="Left" Height="400" Margin="15" VerticalAlignment="Top" Width="700" /> <TextBlock Text="Please perform OAuth process (above), enter Pin (below) when ready, and tap Authenticate:" Margin="15,15,15,5" /> <TextBox Name="PinTextBox" Margin="15,0,15,15" Width="432" HorizontalAlignment="Left" IsEnabled="False" /> <Button Name="AuthenticatePinButton" Content="Authenticate" Margin="15" IsEnabled="False" Click="AuthenticatePinButton_Click" /> </StackPanel> The WebView in the code above is what allows the user to see the Twitter authentication page. The TextBox is for entering the Pin, and the Button invokes code that will take the Pin and allow LINQ to Twitter to complete the authentication process. As you can see, there are several steps to OAuth authentication, but LINQ to Twitter tries to minimize the amount of code you have to write. The two important parts of the code to make this happen are the part that starts the authentication process and the part that completes the authentication process. The following code, from OAuthPage.xaml.cs, shows a couple events that are instrumental in making this process happen: public OAuthPage() { this.InitializeComponent(); this.Loaded += OAuthPage_Loaded; OAuthWebBrowser.LoadCompleted += OAuthWebBrowser_LoadCompleted; } The OAuthWebBrowser_LoadCompleted event handler enables UI controls when the browser is done loading – notice that the TextBox and Button in the previous XAML have their IsEnabled attributes set to False. When the Page.Loaded event is invoked, the OAuthPage_Loaded handler starts the OAuth process, shown here: void OAuthPage_Loaded(object sender, RoutedEventArgs e) { auth = new PinAuthorizer { Credentials = new InMemoryCredentials { ConsumerKey = "", ConsumerSecret = "" }, UseCompression = true, GoToTwitterAuthorization = pageLink => Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => OAuthWebBrowser.Navigate(new Uri(pageLink, UriKind.Absolute))) }; auth.BeginAuthorize(resp => Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => { switch (resp.Status) { case TwitterErrorStatus.Success: break; case TwitterErrorStatus.RequestProcessingException: case TwitterErrorStatus.TwitterApiError: new MessageDialog(resp.Error.ToString(), resp.Message).ShowAsync(); break; } })); } The PinAuthorizer, auth, a field of this class instantiated in the code above, assigns keys to the Credentials property. These are credentials that come from registering an application with Twitter, explained in the LINQ to Twitter documentation, Securing Your Applications. Notice how I use Dispatcher.RunAsync to marshal the web browser navigation back onto the UI thread. Internally, LINQ to Twitter invokes the lambda expression assigned to GoToTwitterAuthorization when starting the OAuth process.  In this case, we want the WebView control to navigate to the Twitter authentication page, which is defined with a default URL in LINQ to Twitter and passed to the GoToTwitterAuthorization lambda as pageLink. Then you need to start the authorization process by calling BeginAuthorize. This starts the OAuth dance, running asynchronously.  LINQ to Twitter invokes the callback assigned to the BeginAuthorize parameter, allowing you to take whatever action you need, based on the Status of the response, resp. As mentioned earlier, this is where the user performs the authentication process, enters the Pin, and clicks authenticate. The handler for authenticate completes the process and saves the authorizer for subsequent use by the application, as shown below: void AuthenticatePinButton_Click(object sender, RoutedEventArgs e) { auth.CompleteAuthorize( PinTextBox.Text, completeResp => Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => { switch (completeResp.Status) { case TwitterErrorStatus.Success: SuspensionManager.SessionState["Authorizer"] = auth; Frame.Navigate(typeof(TweetPage)); break; case TwitterErrorStatus.RequestProcessingException: case TwitterErrorStatus.TwitterApiError: new MessageDialog(completeResp.Error.ToString(), completeResp.Message).ShowAsync(); break; } })); } The PinAuthorizer CompleteAuthorize method takes two parameters: Pin and callback. The Pin is from what the user entered in the TextBox prior to clicking the Authenticate button that invoked this method. The callback handles the response from completing the OAuth process. The completeResp holds information about the results of the operation, indicated by a Status property of type TwitterErrorStatus. On success, the code assigns auth to SessionState. You might remember SessionState from the previous description of TweetPage – this is where the valid authorizer comes from. After saving the authorizer, the code navigates the user back to TweetPage, where they can type in a message, click the Tweet button, and observe that they have successfully tweeted. Summary You’ve seen how to get started with using LINQ to Twitter in a Metro-style application. The generated code contained a SuspensionManager class with way to manage information across multiple pages via its SessionState property. You also saw how LINQ to Twitter performs authorization in two steps of starting the process and completing the process when the user provides a Pin number. Remember to marshal callback thread back onto the UI – you saw earlier how to use Dispatcher.RunAsync to accomplish this. There were a few steps in the process, but LINQ to Twitter did minimize the amount of code you needed to write to make it happen. You can download the MetroOAuthDemo.zip sample on the LINQ to Twitter Samples Page.   @JoeMayo

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  • javascript onmouseover hide a div block

    - by Loki
    SO this is my code so far: JS: <script type="text/javascript"> function Hide(srcField) { var x = srcField.getAttribute('name'); var string = new RegExp("hide_ID",'gi'); switch (x) { case "1": var dataRows= document.getElementsByID("obrazovanje"); alert (dataRows[0].innerHTML); dataRows[0].className.replace('',string); break; case "2": var dataRows= document.getElementsByID("rad_iskustvo"); dataRows[0].className.replace('',string); break; case "3": var dataRows= document.getElementsByID("strani_jezici"); dataRows[0].className.replace('',string); break; case "4": var dataRows= document.getElementsByID("znanja_vjestine"); dataRows[0].className.replace('',string); break; case "5": var dataRows= document.getElementsByID("osobine_interesi"); dataRows[0].className.replace('',string); break; } } </script> CSS: .hide_ID, { display:none } HTML: <a name="1"><h4><span name="1" onmouseover="Hide(this)">OBRAZOVANJE:</span></h4></a> <div ID="obrazovanje"> <ul> <li>2001.-2005. elektrotehnicar</li> <li>2009.-2012. racunarstvo</li> </ul> </div> the idea is that i want to hide the div block when i hover over the title that's in h4, but it doesn't seem to hide it... any ideas? i started using replace but it still didn't work, before that it was just 'dataRows[0].className = "hide_ID"' but that didn't work either.

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  • Is this an example for parametric polymorphism?

    - by mrt181
    Hi i am educating myself oop principles. I would like to know if this is a correct example of Cardellis definition of parametric polymorphism. Please enlighten me. The example is in cfml's script based syntax. <cfcomponent> <cfscript> public numeric function getlength(any arg, string type){ switch (arguments.type){ case "array": return arraylen(arguments.arg); break; case "struct": return structcount(arguments.arg); break; case "string": return len(arguments.arg); break; case "numeric": return len(arguments.arg); break; case "object": // gets the number of parent classes, substracting the railo base class return -1 + arraylen(structfindkey(getmetadata(arguments.arg),"extends","all")); break; default: // throw was added to railo as a user defined function to use it in cfscript throw("InvalidTypeArgument","The provided type argument is invalid for method getlength"); } } </cfscript> </cfcomponent>

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  • Weird SQL Server 2005 Collation difference between varchar() and nvarchar()

    - by richardtallent
    Can someone please explain this: SELECT CASE WHEN CAST('iX' AS nvarchar(20)) > CAST('-X' AS nvarchar(20)) THEN 1 ELSE 0 END, CASE WHEN CAST('iX' AS varchar(20)) > CAST('-X' AS varchar(20)) THEN 1 ELSE 0 END Results: 0 1 SELECT CASE WHEN CAST('i' AS nvarchar(20)) > CAST('-' AS nvarchar(20)) THEN 1 ELSE 0 END, CASE WHEN CAST('i' AS varchar(20)) > CAST('-' AS varchar(20)) THEN 1 ELSE 0 END Results: 1 1 On the first query, the nvarchar() result is not what I'm expecting, and yet removing the X make the nvarchar() sort happen as expected. (My original queries used the '' and N'' literal syntax to distinguish varchar() and nvarchar() rather than CAST() and got the same result.) Collation setting for the database is SQL_Latin1_General_CP1_CI_AS.

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  • Glob function (c) and backup file (file~)

    - by arnoras
    I'm using glob function for a autocompletion function. I'm showing you the problem because it's difficult to explain: matched = ~/.tcsh glob(matched, 0, NULL, &pglob); glob put all matched files in a char ** and when I print it I have: case[0] = .tcshrc case[1] = I should have .tcshrc~ in case[1], but nothing =S, I've seen a flag "GLOB_TILDE" like this " glob(matched, GLOB_TILDE, NULL, &pglob); But it doesn't change anything! Can someone help me?

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  • Is using decimal ranges in a switch impossible in C#?

    - by phobia
    I'm justing starting out learning C# and I've become stuck at something very basic. For my first "app" I thought I'd go for something simple, so I decided for a BMI calculator. The BMI is calculated into a decimal type which I'm now trying to use in a switch statement, but aparently decimal can't be used in a switch? What would be the C# solution for this: decimal bmi = calculate_bmi(h, w); switch (bmi) { case < 18.5: bmi_description = "underweight."; break; case > 25: bmi_description = "overweight"; case > 30: bmi_description = "very overweight"; case > 40: bmi_description = "extreme overweight"; break; }

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  • Why no switch on pointers?

    - by meeselet
    For instance: #include <stdio.h> void why_cant_we_switch_him(void *ptr) { switch (ptr) { case NULL: printf("NULL!\n"); break; default: printf("%p!\n", ptr); break; } } int main(void) { void *foo = "toast"; why_cant_we_switch_him(foo); return 0; } gcc test.c -o test test.c: In function 'why_cant_we_switch_him': test.c:5: error: switch quantity not an integer test.c:6: error: pointers are not permitted as case values Just curious. Is this a technical limitation? EDIT People seem to think there is only one constant pointer expression. Is that is really true, though? For instance, here is a common paradigm in Objective-C (it is really only C aside from NSString, id and nil, which are merely a pointers, so it is still relevant — I just wanted to point out that there is, in fact, a common use for it, despite this being only a technical question): #include <stdio.h> #include <Foundation/Foundation.h> static NSString * const kMyConstantObject = @"Foo"; void why_cant_we_switch_him(id ptr) { switch (ptr) { case kMyConstantObject: // (Note that we are comparing pointers, not string values.) printf("We found him!\n"); break; case nil: printf("He appears to be nil (or NULL, whichever you prefer).\n"); break; default: printf("%p!\n", ptr); break; } } int main(void) { NSString *foo = @"toast"; why_cant_we_switch_him(foo); foo = kMyConstantObject; why_cant_we_switch_him(foo); return 0; } gcc test.c -o test -framework Foundation test.c: In function 'why_cant_we_switch_him': test.c:5: error: switch quantity not an integer test.c:6: error: pointers are not permitted as case values It appears that the reason is that switch only allows integral values (as the compiler warning said). So I suppose a better question would be to ask why this is the case? (though it is probably too late now.)

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  • Scala match question

    - by javier
    Hello to everyone. I came across with an error on my Scala code that I cannot solve by myself (I am new at Scala). I have the following code: def myFunction(list: List[Any]): String = { var strItems : String = ""; list.foreach(item => { strItems += item match { case x:JsonSerializable => x.toJson() case y:String => ("\"" + y + "\"") case _ => item.toString } if(item != list.last) strItems += ","; }) strItems; } The error I am getting is: error: pattern type is incompatible with expected type; found : String required: Unit case y:String = ("\"" + y + "\"") Any idea why? PS: is there a more performant way to code myFunction

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