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  • A few announcements for those in the UK

    - by ScottGu
    This a quick post to announce a few upcoming events for those in the UK. I’ll be presenting in Glasgow, Scotland on March 25th I’m doing a free 5 hour presentation in Glasgow on March 25th. I’ll be covering VS 2010, ASP.NET 4, ASP.NET Web Forms 4, ASP.NET MVC 2, Silverlight and potentially show off a few new things that haven’t been announced yet. You can learn more about the event and register for free here.  There are only a few spots left – so register quickly.  When the event fills up there will be a wait-list – please add yourself to this as we’ll be encouraging people who won’t be able to attend to let us know ahead of time so that we can add more people to the event. I’ll be presenting in Birmingham, England on March 26th I’m doing a free 5 hour presentation in Birmingham (UK) on March 26th. I’ll be covering VS 2010, ASP.NET 4, ASP.NET Web Forms 4, ASP.NET MVC 2, Silverlight and also potentially show off a few new things that haven’t been announced yet. You can learn more about the event and register for free here. The event unfortunately filled up immediately (even before I had a chance to blog it) – but there is a waitlist.  If you’d like to attend please add yourself to it as hopefully a number of people will be able to attend off of it. UK Party at MIX If you are going to MIX and are from the UK send mail to [email protected] (or tweet him @plip) for an invite to a party being organized for UK MIX attendees next Sunday (March 14th).  Knowing the people involved I’m sure the party will be fun. <g> Hope this helps, Scott

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  • SharePoint Apps and Windows Azure

    - by ScottGu
    Last Monday I had an opportunity to present as part of the keynote of this year’s SharePoint Conference.  My segment of the keynote covered the new SharePoint Cloud App Model we are introducing as part of the upcoming SharePoint 2013 and Office 365 releases.  This new app model for SharePoint is additive to the full trust solutions developers write today, and is built around three core tenants: Simplifying the development model and making it consistent between the on-premises version of SharePoint and SharePoint Online provided with Office 365. Making the execution model loosely coupled – and enabling developers to build apps and write code that can run outside of the core SharePoint service. This makes it easy to deploy SharePoint apps using Windows Azure, and avoid having to worry about breaking SharePoint and the apps within it when something is upgraded.  This new loosely coupled model also enables developers to write SharePoint applications that can leverage the full capabilities of the .NET Framework – including ASP.NET Web Forms 4.5, ASP.NET MVC 4, ASP.NET Web API, EF 5, Async, and more. Implementing this loosely coupled model using standard web protocols – like OAuth, JSON, and REST APIs – that enable developers to re-use skills and tools, and easily integrate SharePoint with Web and Mobile application architectures. A video of my talk + demos is now available to watch online: In the talk I walked through building an app from scratch – it showed off how easy it is to build solutions using new SharePoint application, and highlighted a web + workflow + mobile scenario that integrates SharePoint with code hosted on Windows Azure (all built using Visual Studio 2012 and ASP.NET 4.5 – including MVC and Web API). The new SharePoint Cloud App Model is something that I think is pretty exciting, and it is going to make it a lot easier to build SharePoint apps using the full power of both Windows Azure and the .NET Framework.  Using Windows Azure to easily extend SaaS based solutions like Office 365 is also a really natural fit and one that is going to offer a bunch of great developer opportunities.  Hope this helps, Scott  P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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  • Aplicações do SharePoint e Windows Azure

    - by Leniel Macaferi
    Segunda-feira passada eu tive a oportunidade de me apresentar dando uma palestra na SharePoint Conference (em Inglês). Meu segmento na palestra cobriu o novo modelo de Aplicações para Nuvem do SharePoint (SharePoint Cloud App Model) que estamos introduzindo como parte dos próximos lançamentos do SharePoint 2013 e Office 365. Este novo modelo de aplicações para o SharePoint é aditivo para as soluções de total confiança que os desenvolvedores escrevem atualmente, e é construído em torno de três pilares principais: Simplificar o modelo de desenvolvimento tornando-o consistente entre a versão local do SharePoint e a versão online do SharePoint fornecida com o Office 365. Tornar o modelo de execução flexível - permitindo que os desenvolvedores criem aplicações e escrevam código que pode ser executado fora do núcleo do serviço do SharePoint. Isto torna mais fácil implantar aplicações SharePoint usando a Windows Azure, evitando a preocupação com a quebra do SharePoint e das aplicações que rodam dentro dele quando algo é atualizado. Este novo modelo flexível também permite que os desenvolvedores escrevam aplicações do SharePoint que podem alavancar as capacidades do .NET Framework - incluindo ASP.NET Web Forms 4.5, ASP.NET MVC 4, ASP.NET Web API, Entity Framework 5, Async, e mais. Implementar este modelo flexível utilizando protocolos padrão da web - como OAuth, JSON e APIs REST - que permitem aos desenvolvedores reutilizar habilidades e ferramentas, facilmente integrando o SharePoint com arquiteturas Web e arquiteturas para aplicações móveis. Um vídeo da minha palestra + demos está disponível para assistir on-line (em Inglês): Na palestra eu mostrei como construir uma aplicação a partir do zero - ela mostrou como é fácil construir soluções usando a nova aplicação SharePoint, e destacou um cenário web + workflow + móvel que integra o SharePoint com código hospedado na Windows Azure (totalmente construído usando o Visual Studio 2012 e ASP.NET 4.5 - incluindo MVC e Web API). O novo Modelo de Aplicações para Nuvem do SharePoint é algo que eu acho extremamente emocionante, e que vai tornar muito mais fácil criar aplicações SharePoint usando todo o poder da Windows Azure e do .NET Framework. Usar a Windows Azure para estender facilmente soluções baseadas em SaaS como o Office 365 é também algo muito natural e que vai oferecer um monte de ótimas oportunidades para os desenvolvedores.  Espero que ajude, - Scott P.S. Além do blog, eu também estou utilizando o Twitter para atualizações rápidas e para compartilhar links. Siga-me em: twitter.com/ScottGu Texto traduzido do post original por Leniel Macaferi.

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  • ASP.NET GZip Encoding Caveats

    - by Rick Strahl
    GZip encoding in ASP.NET is pretty easy to accomplish using the built-in GZipStream and DeflateStream classes and applying them to the Response.Filter property.  While applying GZip and Deflate behavior is pretty easy there are a few caveats that you have watch out for as I found out today for myself with an application that was throwing up some garbage data. But before looking at caveats let’s review GZip implementation for ASP.NET. ASP.NET GZip/Deflate Basics Response filters basically are applied to the Response.OutputStream and transform it as data is written to it through the ASP.NET Response object. So a Response.Write eventually gets written into the output stream which if a filter is also written through the filter stream’s interface. To perform the actual GZip (and Deflate) encoding typically used by Web pages .NET includes the GZipStream and DeflateStream stream classes which can be readily assigned to the Repsonse.OutputStream. With these two stream classes in place it’s almost trivially easy to create a couple of reusable methods that allow you to compress your HTTP output. In my standard WebUtils utility class (from the West Wind West Wind Web Toolkit) created two static utility methods – IsGZipSupported and GZipEncodePage – that check whether the client supports GZip encoding and then actually encodes the current output (note that although the method includes ‘Page’ in its name this code will work with any ASP.NET output). /// <summary> /// Determines if GZip is supported /// </summary> /// <returns></returns> public static bool IsGZipSupported() { string AcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"]; if (!string.IsNullOrEmpty(AcceptEncoding) && (AcceptEncoding.Contains("gzip") || AcceptEncoding.Contains("deflate"))) return true; return false; } /// <summary> /// Sets up the current page or handler to use GZip through a Response.Filter /// IMPORTANT: /// You have to call this method before any output is generated! /// </summary> public static void GZipEncodePage() { HttpResponse Response = HttpContext.Current.Response; if (IsGZipSupported()) { string AcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"]; if (AcceptEncoding.Contains("deflate")) { Response.Filter = new System.IO.Compression.DeflateStream(Response.Filter, System.IO.Compression.CompressionMode.Compress); Response.Headers.Remove("Content-Encoding"); Response.AppendHeader("Content-Encoding", "deflate"); } else { Response.Filter = new System.IO.Compression.GZipStream(Response.Filter, System.IO.Compression.CompressionMode.Compress); Response.Headers.Remove("Content-Encoding"); Response.AppendHeader("Content-Encoding", "gzip"); } } } As you can see the actual assignment of the Filter is as simple as: Response.Filter = new DeflateStream(Response.Filter, System.IO.Compression.CompressionMode.Compress); which applies the filter to the OutputStream. You also need to ensure that your response reflects the new GZip or Deflate encoding and ensure that any pages that are cached in Proxy servers can differentiate between pages that were encoded with the various different encodings (or no encoding). To use this utility function now is trivially easy: In any ASP.NET code that wants to compress its Response output you simply use: protected void Page_Load(object sender, EventArgs e) { WebUtils.GZipEncodePage(); Entry = WebLogFactory.GetEntry(); var entries = Entry.GetLastEntries(App.Configuration.ShowEntryCount, "pk,Title,SafeTitle,Body,Entered,Feedback,Location,ShowTopAd", "TEntries"); if (entries == null) throw new ApplicationException("Couldn't load WebLog Entries: " + Entry.ErrorMessage); this.repEntries.DataSource = entries; this.repEntries.DataBind(); } Here I use an ASP.NET page, but the above WebUtils.GZipEncode() method call will work in any ASP.NET application type including HTTP Handlers. The only requirement is that the filter needs to be applied before any other output is sent to the OutputStream. For example, in my CallbackHandler service implementation by default output over a certain size is GZip encoded. The output that is generated is JSON or XML and if the output is over 5k in size I apply WebUtils.GZipEncode(): if (sbOutput.Length > GZIP_ENCODE_TRESHOLD) WebUtils.GZipEncodePage(); Response.ContentType = ControlResources.STR_JsonContentType; HttpContext.Current.Response.Write(sbOutput.ToString()); Ok, so you probably get the idea: Encoding GZip/Deflate content is pretty easy. Hold on there Hoss –Watch your Caching Or is it? There are a few caveats that you need to watch out for when dealing with GZip content. The fist issue is that you need to deal with the fact that some clients don’t support GZip or Deflate content. Most modern browsers support it, but if you have a programmatic Http client accessing your content GZip/Deflate support is by no means guaranteed. For example, WinInet Http clients don’t support GZip out of the box – it has to be explicitly implemented. Other low level HTTP clients on other platforms too don’t support GZip out of the box. The problem is that your application, your Web Server and Proxy Servers on the Internet might be caching your generated content. If you return content with GZip once and then again without, either caching is not applied or worse the wrong type of content is returned back to the client from a cache or proxy. The result is an unreadable response for *some clients* which is also very hard to debug and fix once in production. You already saw the issue of Proxy servers addressed in the GZipEncodePage() function: // Allow proxy servers to cache encoded and unencoded versions separately Response.AppendHeader("Vary", "Content-Encoding"); This ensures that any Proxy servers also check for the Content-Encoding HTTP Header to cache their content – not just the URL. The same thing applies if you do OutputCaching in your own ASP.NET code. If you generate output for GZip on an OutputCached page the GZipped content will be cached (either by ASP.NET’s cache or in some cases by the IIS Kernel Cache). But what if the next client doesn’t support GZip? She’ll get served a cached GZip page that won’t decode and she’ll get a page full of garbage. Wholly undesirable. To fix this you need to add some custom OutputCache rules by way of the GetVaryByCustom() HttpApplication method in your global_ASAX file: public override string GetVaryByCustomString(HttpContext context, string custom) { // Override Caching for compression if (custom == "GZIP") { string acceptEncoding = HttpContext.Current.Response.Headers["Content-Encoding"]; if (string.IsNullOrEmpty(acceptEncoding)) return ""; else if (acceptEncoding.Contains("gzip")) return "GZIP"; else if (acceptEncoding.Contains("deflate")) return "DEFLATE"; return ""; } return base.GetVaryByCustomString(context, custom); } In a page that use Output caching you then specify: <%@ OutputCache Duration="180" VaryByParam="none" VaryByCustom="GZIP" %> To use that custom rule. It’s all Fun and Games until ASP.NET throws an Error Ok, so you’re up and running with GZip, you have your caching squared away and your pages that you are applying it to are jamming along. Then BOOM, something strange happens and you get a lovely garbled page that look like this: Lovely isn’t it? What’s happened here is that I have WebUtils.GZipEncode() applied to my page, but there’s an error in the page. The error falls back to the ASP.NET error handler and the error handler removes all existing output (good) and removes all the custom HTTP headers I’ve set manually (usually good, but very bad here). Since I applied the Response.Filter (via GZipEncode) the output is now GZip encoded, but ASP.NET has removed my Content-Encoding header, so the browser receives the GZip encoded content without a notification that it is encoded as GZip. The result is binary output. Here’s what Fiddler says about the raw HTTP header output when an error occurs when GZip encoding was applied: HTTP/1.1 500 Internal Server Error Cache-Control: private Content-Type: text/html; charset=utf-8 Date: Sat, 30 Apr 2011 22:21:08 GMT Content-Length: 2138 Connection: close ?`I?%&/m?{J?J??t??` … binary output striped here Notice: no Content-Encoding header and that’s why we’re seeing this garbage. ASP.NET has stripped the Content-Encoding header but left our filter intact. So how do we fix this? In my applications I typically have a global Application_Error handler set up and in this case I’ve been using that. One thing that you can do in the Application_Error handler is explicitly clear out the Response.Filter and set it to null at the top: protected void Application_Error(object sender, EventArgs e) { // Remove any special filtering especially GZip filtering Response.Filter = null; … } And voila I get my Yellow Screen of Death or my custom generated error output back via uncompressed content. BTW, the same is true for Page level errors handled in Page_Error or ASP.NET MVC Error handling methods in a controller. Another and possibly even better solution is to check whether a filter is attached just before the headers are sent to the client as pointed out by Adam Schroeder in the comments: protected void Application_PreSendRequestHeaders() { // ensure that if GZip/Deflate Encoding is applied that headers are set // also works when error occurs if filters are still active HttpResponse response = HttpContext.Current.Response; if (response.Filter is GZipStream && response.Headers["Content-encoding"] != "gzip") response.AppendHeader("Content-encoding", "gzip"); else if (response.Filter is DeflateStream && response.Headers["Content-encoding"] != "deflate") response.AppendHeader("Content-encoding", "deflate"); } This uses the Application_PreSendRequestHeaders() pipeline event to check for compression encoding in a filter and adjusts the content accordingly. This is actually a better solution since this is generic – it’ll work regardless of how the content is cleaned up. For example, an error Response.Redirect() or short error display might get changed and the filter not cleared and this code actually handles that. Sweet, thanks Adam. It’s unfortunate that ASP.NET doesn’t natively clear out Response.Filters when an error occurs just as it clears the Response and Headers. I can’t see where leaving a Filter in place in an error situation would make any sense, but hey - this is what it is and it’s easy enough to fix as long as you know where to look. Riiiight! IIS and GZip I should also mention that IIS 7 includes good support for compression natively. If you can defer encoding to let IIS perform it for you rather than doing it in your code by all means you should do it! Especially any static or semi-dynamic content that can be made static should be using IIS built-in compression. Dynamic caching is also supported but is a bit more tricky to judge in terms of performance and footprint. John Forsyth has a great article on the benefits and drawbacks of IIS 7 compression which gives some detailed performance comparisons and impact reviews. I’ll post another entry next with some more info on IIS compression since information on it seems to be a bit hard to come by. Related Content Built-in GZip/Deflate Compression in IIS 7.x HttpWebRequest and GZip Responses © Rick Strahl, West Wind Technologies, 2005-2011Posted in ASP.NET   IIS7  

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  • Back to Basics: When does a .NET Assembly Dependency get loaded

    - by Rick Strahl
    When we work on typical day to day applications, it's easy to forget some of the core features of the .NET framework. For me personally it's been a long time since I've learned about some of the underlying CLR system level services even though I rely on them on a daily basis. I often think only about high level application constructs and/or high level framework functionality, but the low level stuff is often just taken for granted. Over the last week at DevConnections I had all sorts of low level discussions with other developers about the inner workings of this or that technology (especially in light of my Low Level ASP.NET Architecture talk and the Razor Hosting talk). One topic that came up a couple of times and ended up a point of confusion even amongst some seasoned developers (including some folks from Microsoft <snicker>) is when assemblies actually load into a .NET process. There are a number of different ways that assemblies are loaded in .NET. When you create a typical project assemblies usually come from: The Assembly reference list of the top level 'executable' project The Assembly references of referenced projects Dynamically loaded at runtime via AppDomain/Reflection loading In addition .NET automatically loads mscorlib (most of the System namespace) the boot process that hosts the .NET runtime in EXE apps, or some other kind of runtime hosting environment (runtime hosting in servers like IIS, SQL Server or COM Interop). In hosting environments the runtime host may also pre-load a bunch of assemblies on its own (for example the ASP.NET host requires all sorts of assemblies just to run itself, before ever routing into your user specific code). Assembly Loading The most obvious source of loaded assemblies is the top level application's assembly reference list. You can add assembly references to a top level application and those assembly references are then available to the application. In a nutshell, referenced assemblies are not immediately loaded - they are loaded on the fly as needed. So regardless of whether you have an assembly reference in a top level project, or a dependent assembly assemblies typically load on an as needed basis, unless explicitly loaded by user code. The same is true of dependent assemblies. To check this out I ran a simple test: I have a utility assembly Westwind.Utilities which is a general purpose library that can work in any type of project. Due to a couple of small requirements for encoding and a logging piece that allows logging Web content (dependency on HttpContext.Current) this utility library has a dependency on System.Web. Now System.Web is a pretty large assembly and generally you'd want to avoid adding it to a non-Web project if it can be helped. So I created a Console Application that loads my utility library: You can see that the top level Console app a reference to Westwind.Utilities and System.Data (beyond the core .NET libs). The Westwind.Utilities project on the other hand has quite a few dependencies including System.Web. I then add a main program that accesses only a simple utillity method in the Westwind.Utilities library that doesn't require any of the classes that access System.Web: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.ReadLine(); } StringUtils.NewStringId() calls into Westwind.Utilities, but it doesn't rely on System.Web. Any guesses what the assembly list looks like when I stop the code on the ReadLine() command? I'll wait here while you think about it… … … So, when I stop on ReadLine() and then fire up Process Explorer and check the assembly list I get: We can see here that .NET has not actually loaded any of the dependencies of the Westwind.Utilities assembly. Also not loaded is the top level System.Data reference even though it's in the dependent assembly list of the top level project. Since this particular function I called only uses core System functionality (contained in mscorlib) there's in fact nothing else loaded beyond the main application and my Westwind.Utilities assembly that contains the method accessed. None of the dependencies of Westwind.Utilities loaded. If you were to open the assembly in a disassembler like Reflector or ILSpy, you would however see all the compiled in dependencies. The referenced assemblies are in the dependency list and they are loadable, but they are not immediately loaded by the application. In other words the C# compiler and .NET linker are smart enough to figure out the dependencies based on the code that actually is referenced from your application and any dependencies cascading down into the dependencies from your top level application into the referenced assemblies. In the example above the usage requirement is pretty obvious since I'm only calling a single static method and then exiting the app, but in more complex applications these dependency relationships become very complicated - however it's all taken care of by the compiler and linker figuring out what types and members are actually referenced and including only those assemblies that are in fact referenced in your code or required by any of your dependencies. The good news here is: That if you are referencing an assembly that has a dependency on something like System.Web in a few places that are not actually accessed by any of your code or any dependent assembly code that you are calling, that assembly is never loaded into memory! Some Hosting Environments pre-load Assemblies The load behavior can vary however. In Console and desktop applications we have full control over assembly loading so we see the core CLR behavior. However other environments like ASP.NET for example will preload referenced assemblies explicitly as part of the startup process - primarily to minimize load conflicts. Specifically ASP.NET pre-loads all assemblies referenced in the assembly list and the /bin folder. So in Web applications it definitely pays to minimize your top level assemblies if they are not used. Understanding when Assemblies Load To clarify and see it actually happen what I described in the first example , let's look at a couple of other scenarios. To see assemblies loading at runtime in real time lets create a utility function to print out loaded assemblies to the console: public static void PrintAssemblies() { var assemblies = AppDomain.CurrentDomain.GetAssemblies(); foreach (var assembly in assemblies) { Console.WriteLine(assembly.GetName()); } } Now let's look at the first scenario where I have class method that references internally uses System.Web. In the first scenario lets add a method to my main program like this: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.ReadLine(); PrintAssemblies(); } public static void WebLogEntry() { var entry = new WebLogEntry(); entry.UpdateFromRequest(); Console.WriteLine(entry.QueryString); } UpdateFromWebRequest() internally accesses HttpContext.Current to read some information of the ASP.NET Request object so it clearly needs a reference System.Web to work. In this first example, the method that holds the calling code is never called, but exists as a static method that can potentially be called externally at some point. What do you think will happen here with the assembly loading? Will System.Web load in this example? No - it doesn't. Because the WebLogEntry() method is never called by the mainline application (or anywhere else) System.Web is not loaded. .NET dynamically loads assemblies as code that needs it is called. No code references the WebLogEntry() method and so System.Web is never loaded. Next, let's add the call to this method, which should trigger System.Web to be loaded because a dependency exists. Let's change the code to: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.WriteLine("--- Before:"); PrintAssemblies(); WebLogEntry(); Console.WriteLine("--- After:"); PrintAssemblies(); Console.ReadLine(); } public static void WebLogEntry() { var entry = new WebLogEntry(); entry.UpdateFromRequest(); Console.WriteLine(entry.QueryString); } Looking at the code now, when do you think System.Web will be loaded? Will the before list include it? Yup System.Web gets loaded, but only after it's actually referenced. In fact, just until before the call to UpdateFromRequest() System.Web is not loaded - it only loads when the method is actually called and requires the reference in the executing code. Moral of the Story So what have we learned - or maybe remembered again? Dependent Assembly References are not pre-loaded when an application starts (by default) Dependent Assemblies that are not referenced by executing code are never loaded Dependent Assemblies are just in time loaded when first referenced in code All of this is nothing new - .NET has always worked like this. But it's good to have a refresher now and then and go through the exercise of seeing it work in action. It's not one of those things we think about everyday, and as I found out last week, I couldn't remember exactly how it worked since it's been so long since I've learned about this. And apparently I'm not the only one as several other people I had discussions with in relation to loaded assemblies also didn't recall exactly what should happen or assumed incorrectly that just having a reference automatically loads the assembly. The moral of the story for me is: Trying at all costs to eliminate an assembly reference from a component is not quite as important as it's often made out to be. For example, the Westwind.Utilities module described above has a logging component, including a Web specific logging entry that supports pulling information from the active HTTP Context. Adding that feature requires a reference to System.Web. Should I worry about this in the scope of this library? Probably not, because if I don't use that one class of nearly a hundred, System.Web never gets pulled into the parent process. IOW, System.Web only loads when I use that specific feature and if I am, well I clearly have to be running in a Web environment anyway to use it realistically. The alternative would be considerably uglier: Pulling out the WebLogEntry class and sticking it into another assembly and breaking up the logging code. In this case - definitely not worth it. So, .NET definitely goes through some pretty nifty optimizations to ensure that it loads only what it needs and in most cases you can just rely on .NET to do the right thing. Sometimes though assembly loading can go wrong (especially when signed and versioned local assemblies are involved), but that's subject for a whole other post…© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  CSharp   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • System.Data.SQLite parameterized queries with multiple values?

    - by Rezzie
    I am trying to do run a bulk deletion using parameterized queries. Currently, I have the following code: pendingDeletions = new SQLiteCommand(@"DELETE FROM [centres] WHERE [name] = $name", conn); foreach (string name in selected) pendingDeletions.Parameters.AddWithValue("$name", centre.Name); pendingDeletions.ExecuteNonQuery(); However, the value of the parameter seems to be overwritten each time and I end up just removing the last centre. What is the correct way to execute a parameterized query with a list of values?

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  • System.Data.SQLite parameter issue

    - by CasperT
    I have the following code: try { //Create connection SQLiteConnection conn = DBConnection.OpenDB(); //Verify user input, normally you give dbType a size, but Text is an exception var uNavnParam = new SQLiteParameter("@uNavnParam", SqlDbType.Text) { Value = uNavn }; var bNavnParam = new SQLiteParameter("@bNavnParam", SqlDbType.Text) { Value = bNavn }; var passwdParam = new SQLiteParameter("@passwdParam", SqlDbType.Text) {Value = passwd}; var pc_idParam = new SQLiteParameter("@pc_idParam", SqlDbType.TinyInt) { Value = pc_id }; var noterParam = new SQLiteParameter("@noterParam", SqlDbType.Text) { Value = noter }; var licens_idParam = new SQLiteParameter("@licens_idParam", SqlDbType.TinyInt) { Value = licens_id }; var insertSQL = new SQLiteCommand("INSERT INTO Brugere (navn, brugernavn, password, pc_id, noter, licens_id)" + "VALUES ('@uNameParam', '@bNavnParam', '@passwdParam', '@pc_idParam', '@noterParam', '@licens_idParam')", conn); insertSQL.Parameters.Add(uNavnParam); //replace paramenter with verified userinput insertSQL.Parameters.Add(bNavnParam); insertSQL.Parameters.Add(passwdParam); insertSQL.Parameters.Add(pc_idParam); insertSQL.Parameters.Add(noterParam); insertSQL.Parameters.Add(licens_idParam); insertSQL.ExecuteNonQuery(); //Execute query //Close connection DBConnection.CloseDB(conn); //Let the user know that it was changed succesfully this.Text = "Succes! Changed!"; } catch(SQLiteException e) { //Catch error MessageBox.Show(e.ToString(), "ALARM"); } It executes perfectly, but when I view my "brugere" table, it has inserted the values: '@uNameParam', '@bNavnParam', '@passwdParam', '@pc_idParam', '@noterParam', '@licens_idParam' literally. Instead of replacing them. I have tried making a breakpoint and checked the parameters, they do have the correct assigned values. So that is not the issue either. I have been tinkering with this a lot now, with no luck, can anyone help? Oh and for reference, here is the OpenDB method from the DBConnection class: public static SQLiteConnection OpenDB() { try { //Gets connectionstring from app.config const string myConnectString = "data source=data;"; var conn = new SQLiteConnection(myConnectString); conn.Open(); return conn; } catch (SQLiteException e) { MessageBox.Show(e.ToString(), "ALARM"); return null; } }

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  • Objective-C and sqlite's DATETIME type.

    - by sant0sk1
    I have a sqlite3 table that I'm trying to map to an object in objective-C. One attribute of the table is 'completed_at' which is stored as a DATETIME. I want to create a property on my objective-C class (which inherits from NSObject) that will map well to the 'completed_at' attribute. Objective-C has an NSDate type but I'm not sure if that will map directly?

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  • SQLite data-types

    - by Alan Harris-Reid
    Hi there, When creating a table in SQLite3, I get confused when confronted with all the possible datatypes which imply similar contents, so could anyone tell me the difference between the following data-types? INT, INTEGER, SMALLINT, TINYINT DEC, DECIMAL LONGCHAR, LONGVARCHAR DATETIME, SMALLDATETIME Is there some documentation somewhere which lists the min./max. capacities of the various data-types? For example, I guess smallint holds a larger maximum value than tinyint, but a smaller value than integer, but I have no idea of what these capacities are. Any help would be appreciated. Alan Harris-Reid

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  • Refernce platform specific System.Data.SQLite

    - by Dmitriy Nagirnyak
    Hi, I am using SQLite for the unit testing and might use it as a database for local development/staging. The System.Data.SQLite has basically 2 versions: x86 and x64. Correct one should be used for the specific platform. I have 64 bit Win7, other guys in the team might use 32-bit OSs. The server's platform is not known at this stage. If I use 32-bit version of the assembly on 64-bit platform I get BadImageFormatException: Could not load file or assembly 'System.Data.SQLite'. I believe similar will happen trying to use 64-bit assembly on 32-bit platform. So my question is what is the best way to reference the SQLite assembly so that it does not depend on the platform and people can just use it? It is ok to use 32-bit version of assembly on a 64-bit platform (Maybe there is a switch for that somewhere?). Thanks, Dmitriy.

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  • How to use LIKE query in sqlite & iPhone

    - by 4thSpace
    I'm using the following for a LIKE query. Is this technique for LIKE correct? selectstmtSearch = nil; if(selectstmtSearch == nil){ const char *sql = "SELECT col1, col2 FROM table1 t1 JOIN table2 t2 ON t1.cityid = t2.cityid where t1.cityname like ?001 order by t1.cityname"; if(sqlite3_prepare_v2(databaseSearch, sql, -1, &selectstmtSearch, NULL) == SQLITE_OK) { sqlite3_bind_text(selectstmtSearch, 1, [[NSString stringWithFormat:@"%%%@%%", searchText] UTF8String], -1, SQLITE_TRANSIENT); } } The problem I'm having is after a few uses of this, I get an error 14 on sqlite3_open(), which is unable to open database. If I replace the LIKE with something such as: SELECT col1, col2 FROM table1 t1 JOIN table2 t2 ON t1.cityid = t2.cityid where t1.cityname = ? order by t1.cityname It works fine. I do open/close the DB before after the above code. Is there a way to troubleshoot exactly why the database can't be opened and what its relationship to my LIKE syntax is?

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  • How to directly store SQLite data in XCode?

    - by Justin
    Hi guys: Searched on here and got some vague answers, so I thought i'd rephrase the problem to get some clearer answers- Right now I have an SQL Lite db that reads/parses information from a pre-formatted .txt file. When I open the app, there is a slight 'lag' as the iDevice parses the info, then gets fetched for the iDevice. I'm just wondering if there's any way to just 'save' all the information directly in the xCode so there's no lag/fetch time? Thank you.

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  • What Features Do You Want To See in .NET 5/C# 5?

    - by Randolpho
    .NET 4 and Visual Studio 2010 are finally here, along with a host of new features. But we wouldn't be who we are if we didn't long for a feature that didn't make the cut, or that was never even considered. So sound off and let the folks at Microsoft know: What features do you want to see in .NET 5? What features do you want to see in C# 5? F#? VB.NET? Before you vote to close: some may find this question too subjective to let stand, but there are other threads that have stood the test of time. Let this one stand as well.

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  • Specify which row to return on SQLite Group By

    - by lozzar
    I'm faced with a bit of a difficult problem. I store all the versions of all documents in a single table. Each document has a unique id, and the version is stored as an integer which is incremented everytime there is a new version. I need a query that will only select the latest version of each document from the database. While using GROUP BY works, it appears that it will break if the versions are not inserted in the database in the order of version (ie. it takes the maximum ROWID which will not always be the latest version). Note, that the latest version of each document will most likely be a different number (ie. document A is at version 3, and document B is at version 6). I'm at my wits end, does anybody know how to do this (select all the documents, but only return a single record for each document_id, and that the record returned should have the highest version number)?

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  • sqlite database, RoR and VCS

    - by ryanprayogo
    What is the common way of dealing with the development.sqlite3 files with VCS (in particular, git)? If I commit this file to the VCS, will it be merged with another developer's copy? Or should each developer run the db:migrate task each time a new migration file is created?

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  • sqlite, C#, UPDATE OR REPLACE

    - by acidzombie24
    I do something like UPDATE OR REPLACE someTable SET a=1, b=2 WHERE c=3 I expect if it doesnt exist it will be inserted into the DBs. But nothing happens and i get no errors. How can i insert data, replace it if it already exist and use a where for the condition (instead of replacing BC of a unique ID)

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  • Python: convert buffer type of SQLITE column into string

    - by Volatil3
    I am new to Python 2.6. I have been trying to fetch date datetime value which is in yyyy-mm-dd hh:m:ss format back in my Python program. On checking the column type in Python I get the error: 'buffer' object has no attribute 'decode'. I want to use the strptime() function to split the date data and use it but I can't find how to convert a buffer to string. The following is a sample of my code (also available here): conn = sqlite3.connect("mrp.db.db", detect_types=sqlite3.PARSE_DECLTYPES) cursor = conn.cursor() qryT = """ SELECT dateDefinitionTest FROM t WHERE IDproject = 4 AND IDstatus = 5 ORDER BY priority, setDate DESC """ rec = (4,4) cursor.execute(qryT,rec) resultsetTasks = cursor.fetchall() cursor.close() # closing the resultset for item in resultsetTasks: taskDetails = {} _f = item[10].decode("utf-8") The exception I get is: 'buffer' object has no attribute 'decode'

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  • Detect if a table contains a column in Android/sqlite

    - by sandis
    So I have an app on the market, and with an update I want to add some columns to the database. No problems so far. But I want to detect if the database in use is missing these columns, and add them if this is the case. I need this to be done dynamically and not just after the update to the new version, because the application is supposed to still be able to import older databases. Normally I would be able to use the PRAGMA query, but Im not sure how to do this with Android. I cant use execSQL since it is a query, and I cant figure out how to use PRAGMA with the query()-function. Ofcourse I could just catch exceptions and then add the column, or always add the columns to each table before I start to work with it, but that is not a neat solution. Cheers,

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  • How to create multiple tables with the same schema using SQLite jdbc

    - by Space_C0wb0y
    I want to split a large table horizontally, and I would like to make sure that all three of them have the same schema. Currently I am using this piece of code to create the tables: statement .executeUpdate("CREATE TABLE AnnotationsMolecularFunction (Id INTEGER PRIMARY KEY ASC AUTOINCREMENT, " + "ProteinId NOT NULL, " + "GOId NOT NULL, " + "UNIQUE (ProteinId, GOId)" + "FOREIGN KEY(ProteinId) REFERENCES Protein(Id))"); There is one such statement for each table. This is bad, because if I decide to change the schema later (which will most certainly happen), I will have to change it three times, which begs for errors, so I would like a way to make sure that the other tables have the same schema without explicitly writing it again. I can use: statement .executeUpdate("CREATE TABLE AnnotationsBiologicalProcess AS SELECT * FROM AnnotationsMolecularFunction"); to create the other tables with the same columns, but the constraints are not aplied. I could of course just generate the same query-string three times with different table-names in Java, but I would like to know if there is an SQL-way of achieving this.

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  • Subsonic SQLite Multiple Files

    - by Marcus Vinicius de LIma
    Hi, I have an application that must be accessed for many users. To optimize the performance I intend to store each user profile information at a independant database file. I need everytime a user login the application, to setup a new provider linked with his own database. All databases have the same structure. So while querying user the commom generated DAL classes must switch for the database file relative the the user. Is there a way for configure SubSonic for doing that switch at runtime? Thanks.

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  • Android SQLite database locale, locking, and version

    - by gdoten
    In some books and online I see these method calls being made after a database is created: db.setLocale(Locale.getDefault()); db.setLockingEnabled(true); db.setVersion(DB_VERSION); Why is this done? As far as I can tell, after creating a new database, the system adds a table named android_metadata with one field named locale and that table has one row with the locale field set to "en_US". Now I assume the column has that value because I am using a U.S. phone, and if I were using a phone from a different region then the locale field would be set appropriately. Can anyone confirm this? I'm guessing that the setLocale method would only be useful in the case that you install a pre-built database onto a phone and then want to change the locale to match the phone's locale. Sound right? The documentation for setLockingEnabled says it defaults to true so there's no need to make that call, right? Lastly, what's with the call to setVersion? I can't find a table that contains this information so I've been assuming that the database file itself stores the version number somewhere. So when I create a database, which requires you to have already specified the version number in the call to the SQLiteOpenHelper constructor, there's no point in calling setVersion. Again, perhaps this method exists for the case of installing a pre-built database to a device and you then wish to change the database's version (though I can't think of when doing this would make sense). Thanks for any insight!

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