asp alliance - Page 48 - Developer IT

ASP.NET MVC static-asset aides/practices

- by shannon

I want to keep assets that are only used by one view in a view-specific folder, so my Search.aspx properly finds images/*.jpg, and helps me maintain my convention: ~/Areas/Candidate/Views/Job/Search.aspx -> ~/Assets/Candidate/Job/Search/images/*.jpg Perhaps with the ability to easily reference controller- or area-common assets manually or automatically: ~/Assets/Candidate/Job/images/*.jpg ~/Assets/Candidate/images/*.jpg If you wonder why I'm doing this, then speak up; I'm probably missing something. But here's why: I don't want stale static assets sitting in my ASP.NET MVC projects, which I expect to be an automatic outcome of the ~/Assets/Images folder: i.e. As a shared asset loses its last reference-count, who knows to delete it, especially with it being so difficult to trace content link validity in MVC projects? How do you, personally, do this? I can imagine, for example: Implement HtmlHelper extension methods for URL-generation. Extending ViewPage and ViewMasterPage with URL-generation methods. Implementing an inbound request filter to search related folders for static assets. and, are there good libraries out there for this? For example, something that also automatically appends timestamps for .JS and .CSS files, writes the / tags for me, and maybe even that allows me to inject includes in the head section from outside head code?

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Error with Property Validation in Form Submission in ASP.NET MVC

- by Maxim Z.

I have a simple form on an ASP.NET MVC site that I'm building. This form is submitted, and then I validate that the form fields aren't null, empty, or improperly formatted. However, when I use ModelState.AddModelError() to indicate validation errors from my controller code, I get an error when my view is re-rendered. In Visual Studio, I get that the following line is highlighted as being the location of the error: <%=Html.TextBox("Email")%> The error is the following: NullReferenceException was unhandled by user code - object reference not set to an instance of an object. My complete code for that textbox is the following: <p> <label for="Email">Your Email:</label> <%=Html.TextBox("Email")%> <%=Html.ValidationMessage("Email", "*") %> </p> Here's how I'm doing that validation in my controller: try { System.Net.Mail.MailAddress address = new System.Net.Mail.MailAddress(email); } catch { ModelState.AddModelError("Email", "Should not be empty or invalid"); } return View(); Note: this applies to all of my fields, not just my Email field, as long as they are invalid.

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Visual Studio 2010 / ASP.NET MVC / Publish

- by SevenCentral

I just did a clean install on Windows 7 x64 Professional with the final release of Visual Studio 2010 Premium. In order to duplicate what I'm experiencing do the following in: Create a new ASP.NET MVC 2 Web Application Right click the project and select Properties On the Web tab, select "Use Local IIS Web Server" Click on Create Virtual Directory Save all Unload the project Edit the project file Change MvcBuildViews to true Save all Reload project Right click the project and select Publish Choose the file system publish method Enter a target location Choose Delete all existing files Select Publish Right click the project Select Publish Each time I do the above I get the following errror: "It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level..." The error originates from obj\debug\package\packagetmp\web.config, relative to the project directory. I can repeat this all day long with any MVC 2 project I've built. In order to fix this problem, I need to set MvcBuildViews to false in the project file. That's not really an option. This wasn't a problem in Visual Studio 2008 and it seems to be an issue with the way the Publish command stages files beneath the project directory. Can anyone else duplicate this error? Is this a bug or by design? Is there a fix, workaround, etc...? Thanks.

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What's missing in ASP.NET MVC?

- by LukaszW.pl

Hello programmers, I think there are not many people who don't think that ASP.NET MVC is one of the greatest technologies Microsoft gave us. It gives full control over the rendered HTML, provides separation of concerns and suits to stateless nature of web. Next versions of framework gaves us new features and tools and it's great, but... what solutions should Microsoft include in new versions of framework? What are biggest gaps in comparison with another web frameworks like PHP or Ruby? What could improve developers productivity? What's missing in ASP.NET MVC?

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server caching problem on ASP.NET MVC page

- by Rita

Hi I have server caching error on ASP.NET MVC Pages. The scenario is like this. I have two applications (1).External Website and (2).Internal Adminsite, both pointing to the same Database. There is one page called EditProfile Page on the External Website that registered customer can update his profile information like Firstname, Lastname and Address…etc. Similarly there is similar functionality on the Internal Adminsite on the page called CustomerProfile Page where the Site Admin can update all these fields. When the user updates the profile information from the Adminsite, those updates are not reflecting back to the Website. Now I tried restarting the Website on IIS and that din’t help. Again I tried both restarting the Website on IIS and opening a new browser, then those updates are reflecting back. I am wondering how I can come out of this caching problem without restarting the site and open a new browser window everytime? Are there any IIS settings that could help? This caching is happening only on couple of tables only and all the updates are showing up in the database. Appreciate your responses. Thanks

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Architecture for new ASP.NET web application

- by Anders Abel

I'm maintaining an application which currently is just a web service (built with WCF) and a database backend. The web service is built in layers with a linq-to-sql data access part with core functionality in an own assembly and on top of that the web service assembly which contains the WCF code. The core assembly also handles all business logic rules (very few actually). The customer now wants a Web interface for the application instead of just accessing it through other applications which are consuming the web service. I'm quite lost on modern web application design, so I would like some advice on what architecture and frameworks to use for the web application. The web application will be using the same core assembly with business rules and the linq-to-sql data access layer as the web service. Some concepts I've thought about are: ASP.NET MVC Webforms AJAX controls - possibly leting the AJAX controls access the existing web service through JSON. Are there any more concepts I should look into? Which one is the best for a fresh project? The development tools are Visual Studio 2008 Team Edition for Developers targeting .NET 3.5. An upgrade to Visual Studio 2010 Premium (or maybe even Ultimate) is possible if it gives any benefits.

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Visual Studio 2010 / ASP.NET MVC 2 / Publish Error

- by SevenCentral

I just did a clean install on Windows 7 x64 Professional with the final release of Visual Studio 2010 Premium. In order to duplicate what I'm experiencing do the following in: Create a new ASP.NET MVC 2 Web Application Right click the project and select Properties On the Web tab, select "Use Local IIS Web Server" Click on Create Virtual Directory Save all Unload the project Edit the project file Change MvcBuildViews to true Save all Reload project Right click the project and select Publish Choose the file system publish method Enter a target location Choose Delete all existing files Select Publish Right click the project Select Publish Each time I do the above I get the following errror: "It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level..." The error originates from obj\debug\package\packagetmp\web.config, relative to the project directory. I can repeat this all day long with any MVC 2 project I've built. In order to fix this problem, I need to set MvcBuildViews to false in the project file. That's not really an option. This wasn't a problem in Visual Studio 2008 and it seems to be an issue with the way the Publish command stages files beneath the project directory. Can anyone else duplicate this error? Is this a bug or by design? Is there a fix, workaround, etc...? Thanks.

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ASP.NET MVC Authorize by Group

- by Jimmo

I have what seems like a common issue with SaaS applications, but have not seen this question on here anywhere. I am using ASP.NET MVC with Forms Authentication. I have implemented a custom membership provider to handle logic, but have one issue (perhaps the issue is in my mental picture of the system). As with many SaaS apps, Customers create accounts and use the app in a way that looks like they are the only ones present (they only see their items, users, etc.) In reality, there are generic controllers and views presenting data depending on their account. When calling something like ValidateUser, I have access to their affiliation in the User object - what I don't have is the context of the request to which to compare it. As an example, One company called ABC goes to abc.mysite.com Another company called XYZ goes to xyz.mysite.com When an ABC user calls http://abc.mysite.com/product/edit/12 I have an [Authorize] attribute on the Edit method in the ProductController to make sure he is signed in and has sufficient permission to do so. If that same ABC user tried to access http://xyz.mysite.com/product/edit/12 I would not want to validate him in the context of that call. In the ValidateUser of the MembershipProvider, I have the information about the user, but not about the request. I can tell that the user is from ABC, but I cannot tell that the request is for XYZ at that point in the code. How should I resolve this?

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ASP.NET MVC Authorize by Subdomain

- by Jimmo

I have what seems like a common issue with SaaS applications, but have not seen this question on here anywhere. I am using ASP.NET MVC with Forms Authentication. I have implemented a custom membership provider to handle logic, but have one issue (perhaps the issue is in my mental picture of the system). As with many SaaS apps, customers create accounts and use the app in a way that looks like they are the only ones present (they only see their items, users, etc.). In reality, there are generic controllers and views presenting data depending on the customer represented in the URL. When calling something like the MembershipProvider.ValidateUser, I have access to the user's customer affiliation in the User object - what I don't have is the context of the request to compare whether it is a data request for the same customer as the user. As an example, One company called ABC goes to abc.mysite.com Another company called XYZ goes to xyz.mysite.com When an ABC user calls http://abc.mysite.com/product/edit/12 I have an [Authorize] attribute on the Edit method in the ProductController to make sure he is signed in and has sufficient permission to do so. If that same ABC user tried to access http://xyz.mysite.com/product/edit/12 I would not want to validate him in the context of that call. In the ValidateUser of the MembershipProvider, I have the information about the user, but not about the request. I can tell that the user is from ABC, but I cannot tell that the request is for XYZ at that point in the code. How should I resolve this?

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Can I import an existing member data used in old ASP to a new ASP.NET membership database? [closed]

- by Rick Brown

I have an old website that I designed and still maintain using old ASP that has a membership database (MS-SQL) that I built from scratch. It is a very simple database that has all the user information in one table (including login info and personal info) and then details and other odds and ends in other tables. It is WAY past time to upgrade this to .NET, especially since I need to add a Paypal payment system into it as soon as I can. I've designed several other sites with membership in .NET, but they have all been from scratch. Is there an easy way to transition from the old ASP site to a new .NET membership database without losing the data? There are hundreds of users with thousands of records relating to those users that I'd rather not lose, if possible. Any ideas on a relatively painless way to do this?

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Error while updating Database record with Entity Framework on ASP.NET MVC Page

- by Rupa

Hi I have an ASP.NET Page that updates registered User Address Details for a selected record. Below is the Update method that i am calling from Controller. When i am calling ApplyPropertyChanges method, I am getting the below error. Did anyone run into the same error while updating the record with Entity Framework. Appreciate your responses. Error Message: The existing object in the ObjectContext is in the Added state. Changes can only be applied when the existing object is in an unchanged or modified state. My Update Method Code: [HttpPost] public bool UpdateAddressDetail([Bind(Prefix = "RegUser")] AddressDetail regUserAddress, FormCollection formData) { regUserAddress.AD_Id = 3; regUserAddress.LastUpdated = HttpContext.User.Identity.Name; regUserAddress.UpdatedOn = DateTime.Now; regUserAddress.AddressType = ((AddressDetail)Session["CurrentAddress"]).AddressType ?? "Primary"; regUserAddress.Phone = ((AddressDetail)Session["CurrentAddress"]).Phone; regUserAddress.Country = ((AddressDetail)Session["CurrentAddress"]).AddressType ?? "USA"; miEntity.ApplyPropertyChanges(regUserAddress.EntityKey.EntitySetName, regUserAddress); miEntity.SaveChanges(); return true; }

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Organazing ASP.Net Single Page Application with Nancy

- by OnesimusUnbound

As a personal project, I'm creating a single page, asp.net web application using Nancy to provide RESTful services to the single page. Due to the complexity of the single page, particularly the JavaScripts used, I've think creating a dedicated project for the client side of web development and another for service side will organize and simplify the development. solution | +-- web / client side (single html page, js, css) | - contains asp.net project, and nancy library | to host the modules in application ptoject folder | +-- application / service (nancy modules, bootstrap for other layer) | . . . and other layers (three teir, domain driven, etc) . Is this a good way of organizing a complex single page application? Am I over-engineering the web app, incurring too much complexity?

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Long running operations (threads) in a web (asp.net) environment

- by rrejc

I have an asp.net (mvc) web site. As the part of the functions I will have to support some long running operations, for example: Initiated from user: User can upload (xml) file to the server. On the server I need to extract file, do some manipulation (insert into the db) etc... This can take from one minute to ten minutes (or even more - depends on file size). Of course I don't want to block the request when the import is running , but I want to redirect user to some progress page where he will have a chance to watch the status, errors or even cancel the import. This operation will not be frequently used, but it may happen that two users at the same time will try to import the data. It would be nice to run the imports in parallel. At the beginning I was thinking to create a new thread in the iis (controller action) and run the import in a new thread. But I am not sure if this is a good idea (to create working threads on a web server). Should I use windows services or any other approach? Initiated from system: - I will have to periodically update lucene index with the new data. - I will have to send mass emails (in the future). Should I implement this as a job in the site and run the job via Quartz.net or should I also create a windows service or something? What are the best practices when it comes to running site "jobs"? Thanks!

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ASP -response-flush-flushes-partial-data

- by Anshu

I am developing a web app with an ASP server side and I use an iframe for data push. An ASP handler flushes every once in a while some javascript to the iframe: context.Response.Write("<script language='javascript'>top.update('lala');</script>"); context.Response.Flush(); My problem is that sometimes, when I receive the data, I don't get the full text. For example I will receive this : update('lala'); One workaround I have is to have a thread flushing '..........' every 500ms. (Then I will receive script...... which will complete my javascript.) However I am sure there must be a way to have Response.Flush() sending the whole chunk of data. Does someone have an idea on how to use properly Response.Flush() ? Thank you!

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Generic ASP.NET MVC Route Conflict

- by Donn Felker

I'm working on a Legacy ASP.NET system. I say legacy because there are NO tests around 90% of the system. I'm trying to fix the routes in this project and I'm running into a issue I wish to solve with generic routes. I have the following routes: routes.MapRoute( "DefaultWithPdn", "{controller}/{action}/{pdn}", new { controller = "", action = "Index", pdn = "" }, null ); routes.MapRoute( "DefaultWithClientId", "{controller}/{action}/{clientId}", new { controller = "", action = "index", clientid = "" }, null ); The problem is that the first route is catching all of the traffic for what I need to be routed to the second route. The route is generic (no controller is defined in the constraint in either route definition) because multiple controllers throughout the entire app share this same premise (sometimes we need a "pdn" sometimes we need a "clientId"). How can I map these generic routes so that they go to the proper controller and action, yet not have one be too greedy? Or can I at all? Are these routes too generic (which is what I'm starting to believe is the case). My only option at this point (AFAIK) is one of the following: In the contraints, apply a regex to match the action values like: (foo|bar|biz|bang) and the same for the controller: (home|customer|products) for each controller. However, this has a problem in the fact that I may need to do this: ~/Foo/Home/123 // Should map to "DefaultwithPdn" ~/Foo/Home/abc // Should map to "DefaultWithClientId" Which means that if the Foo Controller has an action that takes a pdn and another action that takes a clientId (which happens all the time in this app), the wrong route is chosen. To hardcode these contstraints into each possible controller/action combo seems like a lot of duplication to me and I have the feeling I've been looking at the problem for too long so I need another pair of eyes to help out. Can I have generic routes to handle this scenario? Or do I need to have custom routes for each controller with constraints applied to the actions on those routes? Thanks

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How to submit Nothing as a route value to ASP MVC

- by Adam

I have a route with several optional parameters. These are possible search terms in different fields. So, for example, if I have fields key, itemtype and text then I have in global.asax: routes.MapRoute( _ "Search", _ "Admin.aspx/Search/{Key}/{ItemType}/{Text}", _ New With {.controller = "Admin", .action = "Search" .Key = Nothing, .ItemType = Nothing, .Text = Nothing} _ ) My action takes optional parameters: Function Search(Optional ByVal Key As String = Nothing, _ Optional ByVal ItemType As Integer = 0, _ Optional ByVal Text As String = Nothing, _ Optional ByVal OtherText As String = Nothing) It then checks if the Key and Text strings have a non-null (and non-empty) value and adds search terms to the db request as needed. However, is it possible to send in a null value for, for example, Key but still send in a value for Text? If so, what does the URL look like? (Admin.aspx/Search//0/Foo doesn't work :) ) I know I can handle this using a parameter array instead, but wondered if this was possible using the sort of route described? I could of course define some other value as equivalent to null (for example, a space/%20) but is there any way to send a null value in the URL? I'm suspecting not, but thought I'd see if anyone knew of one. I'm using ASP MVC 2 for this project.

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ASP.Net forms authentication - multiple providers

- by Chris Klepeis

I have an ASP.Net 4.0 application, and within it is a folder called "Forum", setup as a sub application in IIS 7. This forum package implements a custom provider for .net membership. The forum is running in .net 3.5. I'd like to setup the main site so that when users login, it logs them into both my site and the forum site. Both the main site and the forum have separate .Net membership tables. How can I specify which provider to use with formsauthentication? right now I have FormsAuthentication.SetAuthCookie(...); this, however, just uses my default provider and does nothing with the provider for the forum I tried setting the forum app and my web app to have the same cookie name, as well as setting the machinekey on each: <machineKey validationKey="AutoGenerate" validation="SHA1" /> no dice. I googled and didnt really come up with any example of how to use multiple providers like I want to. I updated my web.config to have both provideers but this is useless if I cannot specify in my code which one to use.

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ASP.NET MVC Membership, Get new UserID

- by Vishal Bharakhda

I am trying to register a new user and also understand how to get the new userID so i can start creating my own user tables with a userID mapping to the asp.net membership user table. Below is my code: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Register(string userName, string email, string position, string password, string confirmPassword) { ViewData["PasswordLength"] = MembershipService.MinPasswordLength; ViewData["position"] = new SelectList(GetDeveloperPositionList()); if (ValidateRegistration(userName, email, position, password, confirmPassword)) { // Attempt to register the user MembershipCreateStatus createStatus = MembershipService.CreateUser(userName, password, email); if (createStatus == MembershipCreateStatus.Success) { FormsAuth.SignIn(userName, false /* createPersistentCookie */); return RedirectToAction("Index", "Home"); } else { ModelState.AddModelError("_FORM", ErrorCodeToString(createStatus)); } } // If we got this far, something failed, redisplay form return View(); } I've done some research and many sites inform me to use Membership.GetUser().ProviderUserKey; but this throws an error as Membership is NULL. I placed this line of code just above "return RedirectToAction("Index", "Home");" within the if statement. Please can someone advise me on this... Thanks in advance

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Classic ASP application-wide initializations and object caching

- by slack3r

In classic ASP (which I am forced to use), I have a few factory functions, that is, functions that return classes. I use JScript. In one include file I use these factory functions to create some classes that are used throughout the application. This include file is included with the #include directive in all pages. These factory functions do some "heavy lifting" and I don't want them to be executed on every page load. So, to make this clear I have something like this: // factory.inc function make_class(arg1, arg2) { function klass() { //... } // ... Some heavy stuff return klass; } // init.inc, included everywhere  // ... MyClass1 = make_class(myarg01, myarg02); MyClass2 = make_class(myarg11, myarg12); //... How can I achieve the same effect without calling make_class on every page load? I know that I can't cache the classes in the Application object I can't use the Application_OnStart hook in Global.asa I could probably create a scripting component, but I really don't want to do that So, is there something else I can do? Maybe some way to achieve caching of these classes, which are really objects in JScript. PS: [further clarification] In the above code "heavy stuff" is not so heavy, but I just want to know if there's a way to avoid it being executed all the time. It reads database meta information, builds a table of the primary keys in the database and another table that resolves strings to classes, etc.

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Filp route value in asp.net mvc routes

- by Herman

Hi all, I am new to asp.net mvc, so please bear with me. We have the following route dictionary setup. routes.MapRoute( "Default", // Route name "{language}/{controller}/{action}/{id}", // URL with parameters new { language = "en", controller = "Home", action = "Index", id = "" } // Parameter defaults ); for any given page in our app, we to render a link to the a french version of the same page. For example, the page: http://www.example.com/en/home should have link on that page that points to http://www.example.com/fr/home Now I have the following UrlHelper extension method public static string FilpLanguage(this UrlHelper urlHelper) { var data = urlHelper.RequestContext.RouteData; if (System.Threading.Thread.CurrentThread.CurrentCulture == CultureInfo.GetCultureInfoByIetfLanguageTag("en-CA")) data.Values["language"] = "fr"; else data.Values["language"] = "en"; return urlHelper.RouteUrl(data.Values.Where(item => item.Value != null)); } However, calling FilpLanguage on www.example.com/en/home will return the following URL: www.example.com/en/home?current=[,] Am I missing something here? where did the current parameter come from? Thanks in advance.

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Deploying Asp.net MVC web application [migrated]

- by Pankaj Upadhyay

I have been trying to find a neat tutorial, guide or step by step instructions for deploying an Asp.net MVC3 webapp but have found nothing so far. Everyone talks about his version of the stroy and different type of MVC versions. Right now, I have build a simple Asp.net MVC web application which i need to deploy on my shared hosting account. In a very simple manner, I need to know which files should i copy. Do i upload everything in my webproject directory to the server including the controller directory, views, models, content and bin directory ?. What about the Global.asax, web.config, packages.config, myapp.publish.xml. In short, I have no idea which files should be uploaded and which should be not. I am sure of one thing that i need few(MVC and Razor dlls) following dlls in bin directory. Just treat me as someone who has never deployed any website NOTE:- I don't have VS SP1 installed and it doesn't install either. Basically i need a manual procedure.

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Visual Studio 2010 / ASP.NET MVC 2 / Publish

- by SevenCentral

I just did a clean install on Windows 7 x64 Professional with the final release of Visual Studio 2010 Premium. In order to duplicate what I'm experiencing do the following in: Create a new ASP.NET MVC 2 Web Application Right click the project and select Properties On the Web tab, select "Use Local IIS Web Server" Click on Create Virtual Directory Save all Unload the project Edit the project file Change MvcBuildViews to true Save all Reload project Right click the project and select Publish Choose the file system publish method Enter a target location Choose Delete all existing files Select Publish Right click the project Select Publish Each time I do the above I get the following errror: "It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level..." The error originates from obj\debug\package\packagetmp\web.config, relative to the project directory. I can repeat this all day long with any MVC 2 project I've built. In order to fix this problem, I need to set MvcBuildViews to false in the project file. That's not really an option. This wasn't a problem in Visual Studio 2008 and it seems to be an issue with the way the Publish command stages files beneath the project directory. Can anyone else duplicate this error? Is this a bug or by design? Is there a fix, workaround, etc...? Thanks.

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Why would he say "We don't want to support MVC3"?

- by MadBurn

I work in a small shop at a fairly big company doing intranet web applications. By small, I mean there is 1 other guy in my position... and he graduated with me last December. (we aren't the only IT, but the only ones in our field) We are switching out an old COBOL system and converting it's only used application suite to a Web App. My company has contracted to a Web Application firm to help with this process who has chosen ASP.NET MVC, during one of the important meetings I asked if they will be using MVC2 or MVC3. Their lead developer said: "MVC2, we don't want to support MVC3. haha" My question is, why is this? This was several months ago and I've been doing extensive and self training gearing up for the MVC switch. From everything I am understanding, MVC3 is just like MVC2 if you don't use Razor and it fixes a number of smaller bugs that MVC2 had. So in my eyes, I can't see any reason to NOT use MCV3. There has to be something I'm missing. Since I don't really have any mentors to turn to in the real world, I'm coming here. What problems are there with MVC3 that might possibly lead him to say this that I'm missing?

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Javascript/Jquery pop-up window in Asp.Net MVC4

- by Mark

Below I have a "button" (just a span with an icon) that creates a pop-up view of a div in my application to allow users to compare information in seperate windows. However, I get and Asp.Net Error as follows: **Server Error in '/' Application. The resource cannot be found. Requested URL: /Home/[object Object]** Does anyone have an Idea of why this is happending? Below is my code: <div class="module_actions"> <div class="actions"> <span class="icon-expand2 pop-out"></span> </div> </div> <script> $(document).ajaxSuccess(function () { var Clone = $(".pop-out").click(function () { $(this).parents(".module").clone().appendTo("#NewWindow"); }); $(".pop-out").click(function popitup(url) { LeftPosition = (screen.width) ? (screen.width - 400) / 1 : 0; TopPosition = (screen.height) ? (screen.height - 700) / 1 : 0; var sheight = (screen.height) * 0.5; var swidth = (screen.width) * 0.5; settings = 'height=' + sheight + ',width=' + swidth + ',top=' + TopPosition + ',left=' + LeftPosition + ',scrollbars=yes,resizable=yes,toolbar=no,status=no,menu=no, directories=no,titlebar=no,location=no,addressbar=no' newwindow = window.open(url, '/Index', settings); if (window.focus) { newwindow.focus() } return false; }); });

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Asynchronous Streaming in ASP.NET WebApi

- by andresv

Hi everyone, if you use the cool MVC4 WebApi you might encounter yourself in a common situation where you need to return a rather large amount of data (most probably from a database) and you want to accomplish two things: Use streaming so the client fetch the data as needed, and that directly correlates to more fetching in the server side (from our database, for example) without consuming large amounts of memory. Leverage the new MVC4 WebApi and .NET 4.5 async/await asynchronous execution model to free ASP.NET Threadpool threads (if possible). So, #1 and #2 are not directly related to each other and we could implement our code fulfilling one or the other, or both. The main point about #1 is that we want our method to immediately return to the caller a stream, and that client side stream be represented by a server side stream that gets written (and its related database fetch) only when needed. In this case we would need some form of "state machine" that keeps running in the server and "knows" what is the next thing to fetch into the output stream when the client ask for more content. This technique is generally called a "continuation" and is nothing new in .NET, in fact using an IEnumerable<> interface and the "yield return" keyword does exactly that, so our first impulse might be to write our WebApi method more or less like this: public IEnumerable<Metadata> Get([FromUri] int accountId) { // Execute the command and get a reader using (var reader = GetMetadataListReader(accountId)) { // Read rows asynchronously, put data into buffer and write asynchronously while (reader.Read()) { yield return MapRecord(reader); } } } While the above method works, unfortunately it doesn't accomplish our objective of returning immediately to the caller, and that's because the MVC WebApi infrastructure doesn't yet recognize our intentions and when it finds an IEnumerable return value, enumerates it before returning to the client its values. To prove my point, I can code a test method that calls this method, for example: [TestMethod] public void StreamedDownload() { var baseUrl = @"http://localhost:57771/api/metadata/1"; var client = new HttpClient(); var sw = Stopwatch.StartNew(); var stream = client.GetStreamAsync(baseUrl).Result; sw.Stop(); Debug.WriteLine("Elapsed time Call: {0}ms", sw.ElapsedMilliseconds); } So, I would expect the line "var stream = client.GetStreamAsync(baseUrl).Result" returns immediately without server-side fetching of all data in the database reader, and this didn't happened. To make the behavior more evident, you could insert a wait time (like Thread.Sleep(1000);) inside the "while" loop, and you will see that the client call (GetStreamAsync) is not going to return control after n seconds (being n == number of reader records being fetched).Ok, we know this doesn't work, and the question would be: is there a way to do it?Fortunately, YES! and is not very difficult although a little more convoluted than our simple IEnumerable return value. Maybe in the future this scenario will be automatically detected and supported in MVC/WebApi.The solution to our needs is to use a very handy class named PushStreamContent and then our method signature needs to change to accommodate this, returning an HttpResponseMessage instead of our previously used IEnumerable<>. The final code will be something like this: public HttpResponseMessage Get([FromUri] int accountId) { HttpResponseMessage response = Request.CreateResponse(); // Create push content with a delegate that will get called when it is time to write out // the response. response.Content = new PushStreamContent( async (outputStream, httpContent, transportContext) => { try { // Execute the command and get a reader using (var reader = GetMetadataListReader(accountId)) { // Read rows asynchronously, put data into buffer and write asynchronously while (await reader.ReadAsync()) { var rec = MapRecord(reader); var str = await JsonConvert.SerializeObjectAsync(rec); var buffer = UTF8Encoding.UTF8.GetBytes(str); // Write out data to output stream await outputStream.WriteAsync(buffer, 0, buffer.Length); } } } catch(HttpException ex) { if (ex.ErrorCode == -2147023667) // The remote host closed the connection. { return; } } finally { // Close output stream as we are done outputStream.Close(); } }); return response; } As an extra bonus, all involved classes used already support async/await asynchronous execution model, so taking advantage of that was very easy. Please note that the PushStreamContent class receives in its constructor a lambda (specifically an Action) and we decorated our anonymous method with the async keyword (not a very well known technique but quite handy) so we can await over the I/O intensive calls we execute like reading from the database reader, serializing our entity and finally writing to the output stream. Well, if we execute the test again we will immediately notice that the a line returns immediately and then the rest of the server code is executed only when the client reads through the obtained stream, therefore we get low memory usage and far greater scalability for our beloved application serving big chunks of data.Enjoy!Andrés.

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