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• WPF/.NET data access models - resource recommendations

  - by jasonk

  We're in the early design/prep phases of transferring/updating a rather large "legacy" 3 tier client-server app to a new version. We’re looking at doing WPF over Winforms as it appears to be the direction Microsoft is pushing development of the future and we’d like the maximize the life cycle/span of the apps. That said during the rewrite we’d like to make as many changes to our data access/presentation model to improve performance as much as possible up front as many. I’ve been doing some research along that vein but the vast majority of the resources I've found that discuss WPF focus only simple data tracking apps or focus on the very basics UI design/controls. The few items that even discuss data presentation are fairly elementary in depth. Are there any books/articles/recommended reading/other resources recommended for development related to large enterprise level business apps? Any “gotchas” that should/could be avoided? General advice to minimize the time underwater

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• Django gives "I/O operation on closed file" error when reading from a saved ImageField

  - by Rob Osborne

  I have a model with two image fields, a source image and a thumbnail. When I update the new source image, save it and then try to read the source image to crop/scale it to a thumbnail I get an "I/O operation on closed file" error from PIL. If I update the source image, don't save the source image, and then try to read the source image to crop/scale, I get an "attempting to read from closed file" error from PIL. In both cases the source image is actually saved and available in later request/response loops. If I don't crop/scale in a single request/response loop but instead upload on one page and then crop/scale in another page this all works fine. This seems to be a cached buffer being reused some how, either by PIL or by the Django file storage. Any ideas on how to make an ImageField readable after saving?

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• Database Modelling - Conceptually different entities but with near identical fields

  - by Andrew Shepherd

  Suppose you have two sets of conceptual entities: MarketPriceDataSet which has multiple ForwardPriceEntries PoolPriceForecastDataSet which has multiple PoolPriceForecastEntry Both different child objects have near identical fields: ForwardPriceEntry has MarketPriceDataSetId (foreign key to parent table) StartDate EndDate SimulationItemId ForwardPrice PoolPriceForecastEntry has PoolPriceForecastDataSetId (foreign key to parent table) StartDate EndDate SimulationItemId ForecastPoolPrice If I modelled them as separate tables, the only difference would be the foreign key, and the name of the price field. There has been a debate as to whether the two near identical tables should be merged into one. Options I've thought of to model this is: Just keep them as two independent, separate tables Have both sets in the one table with an additional "type" field, and a parent_id equalling a foreign key to either parent table. This would sacrifice referential integrity checks. Have both sets in the one table with an additional "type" field, and create a complicated sequence of joining tables to maintain referential integrity. What do you think I should do, and why?

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• how do I migrate Datamapper on appengine

  - by Roy

  I've changed my model from class Place include DataMapper::Resource has n, :trails property :id, Serial property :name, String, :length => 140 property :tag, String, :required => true timestamps :at end to class Place include DataMapper::Resource has n, :trails property :id, Serial property :name, String, :length => 140 property :tag, String, :required => true property :trail_count, Integer, :default => 0 timestamps :at end I just added "property :trail_count, Integer, :default = 0" and i want to migrate the existing appengine table to have the extra field "trail_count" i've read that DataMapper.auto_upgrade! should do it. but i get an error "undefined method `auto_upgrade!' for DataMapper:Module" can you please help How do i migrate the DM models?

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• Rails best practice on conditional parameters in a controller action

  - by randombits

  I have a controller create action looks for one or more parameters in the following ruleset. Let's say we have two parameters, foo and bar. The rules are the following: 1) if foo doesn't exist in the parameter list, bar must. 2) if bar doesn't exist in the parameter list, foo must. 3) they can both co-exist. they can't both be omitted (that's redundant with my rules above :) ) Can anyone show an example in Rails on how this is handled in the controller? Should I use a before_filter? Would appreciate some guidance as this isn't something that ActiveRecord validates.. so I'd need to build an error message to the user directly from controller logic, not model logic. For bonus points, I output the error in XML, so if you can show how that's done, that'd be great. Hypothetically let's call the resource "Lorem", so it is created via http://foo/lorem.xml and we have lorem_controller.rb.

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• WebService: Firefox can't establish a connection to the server at 192.168.10.203:8080

  - by hp1

  Hi, I am trying to create a WebService. I am not able to access the URL. If I try to connect to http://192.168.10.203:8080/EchoBeanService/EchoBean?wsdl I get an error: Firefox can't establish a connection to the server at 192.168.10.203:8080 However, if I am able to connect to the using localhost in the URL: http://localhost:8080/EchoBeanService/EchoBean?wsdl Echo.java package services; public interface Echo { public String printEcho(); public String printEchoParam(String str); } EchoBean.java package model; import javax.jws.WebService; import javax.ejb.Stateless; import javax.jws.WebMethod; import services.Echo; @Stateless @WebService public class EchoBean implements Echo { public EchoBean(){} @WebMethod public String printEcho(){ return "WebServices Echo "; } @WebMethod public String printEchoParam(String str){ return ("In PrintEcho( String " + str +" )" ); } } -H

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• How do I get a right outer join in L2E?

  - by Dan

  I have two tables that I set up through the VS Entity Data Model Diagram tool. I'm trying to do a right outer join and it doesn't return results from the 2nd table. I have set up a 0..1 to MANY relationship from the diagram tool. When I run a Linq-To-Entities query, it still defaults to an INNER JOIN. From my understanding of entities, if I set up the relationship using VS, when I join the tables, it should automagically figure out the join syntax based on the relationship I supply. It doesn't seem to be doing that. I am using EF v1 (not Linq-to-Sql). Query I'm running: from s in SomeTable join t in SomeOtherTable on s.ID equals t.ID select new { s.MyFieldName, t.MyOtherFieldName }

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• Javascript does not work on IIS

  - by Cat Mitch

  I have a .NET library executing as part of our website that renders HTML to image formats. It uses the IE rendering engine, and will happily run any javascript if present to do the rendering. The problem is we just moved the code to a new server, and javascript seems to be disabled. I tried changing (briefly the Application Pools Process Model Identity from NetworkService to LocalSystem, and that worked fine. Hence it must be a permissions problem. So my questions are this: 1) What is the specific permission I need to set to allow the IE rendering engine to execute javascript, inside the IIS application pool? 2) What is the best way to enable that in my application pool? Do I just somehow set it in NetworkService, or create a new identify (how is that done?) Thanks!

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• IDENTITY_INSERT is set to off error

  - by kingrichard2005

  I have a MVC web application with a table in the model that I would like to add to. I have the primary key set along with the other data fields, but every time I try to add to the table, I get the following error: "Cannot insert explicit value for identity column in table 'TABLE_NAME' when IDENTITY_INSERT is set to OFF." I'm not sure why this problem is coming up, I have the primary key set as the identity and it is also set to auto increment in the Visual Studio table designer. Is there any way I can adjust the IDENTITY_INSERT parameter in the table designer in Visual Studio?? Or is there some other issue that might be causing this.

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• How to create mapping for a List<SomeNativeType> in FluentNhibernate ?

  - by Mahesh Velaga

  Hi all, I am trying to create a mapping file for the following Model using Fluent NHibernate. But, I am not sure of how to do the mapping for the List in the mapping file. public class MyClass { public virtual Guid Id { get; set; } public virtual string Name { get; set; } public virtual List<string> MagicStrings { get; set; } } public class EnvironmentMapping : ClassMap<Models.Environment> { public EnvironmentMapping() { Id(x => x.Id); Map(x => x.Name); //HasMany(x => string) What should this be ? } } Help in this regard is much appreciated. Thanks!

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• Using Sculpture with NHibernate or Entity Framework

  - by Sergei

  I recently ran across this open-source project: http://www.codeplex.com/Sculpture Sculpture is a code-generator which allows you to design your domain model and then use persistence 'molds' such as NHibernate/EF and probably more to generate repositories. It takes care of all the mapping and Data access generation. It looks like it does a heck of a lot more, but i'm pretty much sold at this point. However, i would like to know if anyone here used this for real-world solutions. If so, how well does it scale? How did the generated DAL work for you?

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• Out-Of-Memory while doing Core Data migration

  - by Kamchatka

  Hello, I'm migrating a CoreData model between two versions of an application. I was storing binary data as blobs in the previous version and I want to take them out of the blobs for performance. My issue is that during the migration it seems that Core Data loads everything into memory which leads to Low Memory Warnings and then to my app being killed. Apple documentation suggests the following : http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmCustomizingTheProcess.html#//apple_ref/doc/uid/TP40005510-SW9 However, it seems to rely on the fact that the large objects are applied different mapping. In my case, all the objects are basically the same and the same mapping has to be applied to each of them. I don't see in this case how I could apply their technique. How should I handle a migration with very large objects ?

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• Form to sort an index in rails

  - by shmichael

  I'm a newcomer to Rails. I want to build a simple form that determines the sort order of a list. I've implemented a form in the likes of - <%= radio_button_tag :sort, "rating" %> <%= label_tag :sort_rating, "order by rating" %> <%= radio_button_tag :sort, "name" %> <%= label_tag :sort_name, "order by name" %> And now I am unsure how to implement the sort at the controller/model level. The aspects I am puzzled about are: Where should the sort be performed How could the sort parameter be persisted How could the code be reused Right now, I can't even get the selected sort method to remain selected after a submit. I would most appreciate any guidance or reference to an example.

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• Posting a form with anchor link at the end?

  - by Marcus

  I have a form for comments like the one below but after the form is posted I wish to navigate to http://www.myurl.com/mypage#commentform but I don't know how to do this. Instead of changing my form maybe there is a way to return a View with my model and add #commentform to my url? <div id="commentform"> <h2>Leave a comment</h2> <% using (Html.BeginForm("Comment","Post", FormMethod.Post)) %> <% { %> <div> <%=Html.EditorFor(post => post.Comment) %> <div class="editor-button"> <input type="submit" value="Comment" /> </div> </div> <% } %> </div>

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• Ruby on Rails - f.error_messages not showing up

  - by Brian Roisentul

  Hi, I've read many posts about this issue but I never got this to work. My model looks like this: class Announcement < ActiveRecord::Base validates_presence_of :title, :description end My controller's create method(only its relevant part) looks like this: def create respond_to do |format| if @announcement.save flash[:notice] = 'Announcement was successfully created.' format.html { redirect_to(@announcement) } format.xml { render :xml => @announcement, :status => :created, :location => @announcement } else @announcement = Announcement.new @provinces = Province.all @types = AnnouncementType.all @categories = Tag.find_by_sql 'select * from tags where parent_id=0 order by name asc' @subcategories= '' format.html { render :action => "new" } #new_announcement_path format.xml { render :xml => @announcement.errors, :status => :unprocessable_entity } end end end My form looks like this: <% form_for(@announcement) do |f| %> <%= error_messages_for 'announcement' %> <!--I've also treid f.error_messages--> ... What am I doing wrong?

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• Mixing Transaction Script pattern with DDD/CQRS

  - by Herman

  Hi all, Here is the situation, in order to support our legacy system, we need to insert to a table whenever a user logs in. This is basically an CRUD operation, so it doesn't really make sense to create repository/entity/command/event for this since this doesn't tie to any business rules at all. The only benefit to create a CQRS command is that this database write can happen asynchronously under that model. Which is a better route to take? Use CQRS, and then call a stored proc. when handling that command? Just call database directly in the controller (I am using asp.net mvc)

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• Chrome Extension contenteditable get and set caret position

  - by jwize

  I am creating an extension where I need to insert a link into the gmail window. I am able to create a simple extension button in the top of the window and execute code that does replaces all the links. Now, I want to do add links in the contenteditable section as I type. It seems like there should be a simple way to replace text with a link in the document object model. If this is not true I need to do three things. Insert text from the current caret position Capture the caret position. Set the caret position by its offset. I have tried using window.getSelection within the gmail context(that is a body element that is set to contenteditable and embedded inside an iframe in the gmail tab) to get the current range and position. The selection is always empty and contains no ranges regardless of whether text is selected or not.

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• Ruby on Rails: attr_accessor for submodels

  - by williamjones

  I'm working with some models where a lot of a given model's key attributes are actually stored in a submodel. Example: class WikiArticle has_many :revisions has_one :current_revision, :class_name => "Revision", :order => "created_at DESC" end class Revision has_one :wiki_article end The Revision class has a ton of database fields, and the WikiArticle has very few. However, I often have to access a Revision's fields from the context of a WikiArticle. The most important case of this is probably on creating an article. I've been doing that with lots of methods that look like this, one for each field: def description if @description @description elsif current_revision current_revision.description else "" end end def description=(string) @description = string end And then on my save, I save @description into a new revision. This whole thing reminds me a lot of attr_accessor, only it doesn't seem like I can get attr_accessor to do what I need. How can I define an attr_submodel_accessor such that I could just give field names and have it automatically create all those methods the way attr_accessor does?

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• Entity framework (3.5): How to translate a certain LINQ query to eSQL?

  - by Sebastian P.R. Gingter

  Hi there, I have the following LINQ query that I need to translate to Entity SQL /eSQL): return (ObjectQuery<User>) from user in Users where !user.Roles.Any(r => r.AnIntegerProperty < 0) select user; User.Roles is an navigation property to the n:m relation to Roles and there also is a Role.Users navigation property the other way round. There aren't User_Roles or Roles_User Entities available in the model, and I can't add these. I also can't use the LINQ statement here, because I need to add .OrderBy("it." + propertyname) (comes from another source, can't change that too) later on which is not possible if the ObjectQuery is build with linq. So how do I translate this to eSQL? And where can I find good eSQL samples? I searched for a whole day until now and must admit that eSQL reference is lousy and there aren't any usable examples around the web.

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• C++ : Lack of Standardization at the Binary Level

  - by Nawaz

  Why ISO/ANSI didn't standardize C++ at the binary level? There are many portability issues with C++, which is only because of lack of it's standardization at the binary level. Don Box writes, (quoting from his book Essential COM, chapter COM As A Better C++) C++ and Portability Once the decision is made to distribute a C++ class as a DLL, one is faced with one of the fundamental weaknesses of C++, that is, lack of standardization at the binary level. Although the ISO/ANSI C++ Draft Working Paper attempts to codify which programs will compile and what the semantic effects of running them will be, it makes no attempt to standardize the binary runtime model of C++. The first time this problem will become evident is when a client tries to link against the FastString DLL's import library from a C++ developement environment other than the one used to build the FastString DLL. Are there more benefits Or loss of this lack of binary standardization?

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• Doctrine enum type by value

  - by MitMaro

  I have a column in a table defined as following in my yaml file: myTable: columns: value: type: enum length: 2 values: ['yes', 'no'] In the code I am trying to insert data into this table but I can't figure out a way to insert the data using the enum text value (ie. 'yes' or 'no'). What I was trying was is something like this: $obj = new myTable(); // the model for this table $obj->value = 'yes'; // if I use the numerical value for this it works I am using Doctrine 1.1.0.

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• View bound to paged collection view not updating all of the time.

  - by Thomas

  I new to silverlight and trying to make a business application using the mvvm pattern and ria services. I have a view model class that contains a PagedCollectoinView and it is set to the item source of a datagrid. When I update the PagedCollectionView the datagrid is only updated the first time then after that subsequent changes to the data to not reflect in the view until after another edit. Things seem to be delayed one edit. Below is a summarized example of my xaml and code behind. This is the code for my view model public class CustomerContactLinks : INotifyPropertyChanged { private ObservableCollection<CustomerContactLink> _CustomerContact; public ObservableCollection<CustomerContactLink> CustomerContact { get { if (_CustomerContact == null) _CustomerContact = new ObservableCollection<CustomerContactLink>(); return _CustomerContact; } set { _CustomerContact = value; } } private PagedCollectionView _CustomerContactPaged; public PagedCollectionView CustomerContactPaged { get { if (_CustomerContactPaged == null) _CustomerContactPaged = new PagedCollectionView(CustomerContact); return _CustomerContactPaged; } } private TicketSystemDataContext _ctx; public TicketSystemDataContext ctx { get { if (_ctx == null) _ctx = new TicketSystemDataContext(); return _ctx; } } public void GetAll() { ctx.Load(ctx.GetCustomerContactInfoQuery(), LoadCustomerContactsComplete, null); } private void LoadCustomerContactsComplete(LoadOperation<CustomerContactLink> lo) { foreach (var entity in lo.Entities) { CustomerContact.Add(entity as CustomerContactLink); } } #region INotifyPropertyChanged Members public event PropertyChangedEventHandler PropertyChanged; private void RaisePropertyChanged(string propertyName) { if (PropertyChanged != null) { this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } #endregion } Here is the basics of my XAML <Data:DataGrid x:Name="GridCustomers" MinHeight="100" MaxWidth="1000" IsReadOnly="True" AutoGenerateColumns="False"> <Data:DataGrid.Columns> <Data:DataGridTextColumn Header="First Name" Binding="{Binding Customer.FirstName}" Width="105" /> <Data:DataGridTextColumn Header="MI" Binding="{Binding Customer.MiddleName}" Width="35" /> <Data:DataGridTextColumn Header="Last Name" Binding="{Binding Customer.LastName}" Width="105"/> <Data:DataGridTextColumn Header="Address1" Binding="{Binding Contact.Address1}" Width="130"/> <Data:DataGridTextColumn Header="Address2" Binding="{Binding Contact.Address2}" Width="130"/> <Data:DataGridTextColumn Header="City" Binding="{Binding Contact.City}" Width="110"/> <Data:DataGridTextColumn Header="State" Binding="{Binding Contact.State}" Width="50"/> <Data:DataGridTextColumn Header="Zip" Binding="{Binding Contact.Zip}" Width="45"/> <Data:DataGridTextColumn Header="Home" Binding="{Binding Contact.PhoneHome}" Width="85"/> <Data:DataGridTextColumn Header="Cell" Binding="{Binding Contact.PhoneCell}" Width="85"/> <Data:DataGridTextColumn Header="Email" Binding="{Binding Contact.Email}" Width="118"/> </Data:DataGrid.Columns> </Data:DataGrid> <DataForm:DataForm x:Name="CustomerDetails" Header="Customer Details" AutoGenerateFields="False" AutoEdit="False" AutoCommit="False" CommandButtonsVisibility="Edit" Width="1000" Margin="0,5,0,0"> <DataForm:DataForm.EditTemplate> </DataForm:DataForm.EditTemplate> </DataForm:DataForm> And here is my code behind public Customers() { InitializeComponent(); BusyDialogIndicator.IsBusy = true; Loaded += new RoutedEventHandler(Customers_Loaded); CustomerDetails.BeginningEdit += new EventHandler(CustomerDetails_BeginningEdit); } void CustomerDetails_BeginningEdit(object sender, System.ComponentModel.CancelEventArgs e) { CustomerContacts.CustomerContactPaged.EditItem(CustomerDetails.CurrentItem); } private void Customers_Loaded(object sender, RoutedEventArgs e) { CustomerContacts = new CustomerContactLinks(); CustomerContacts.GetAll(); GridCustomers.ItemsSource = CustomerContacts.CustomerContactPaged; GridCustomerPager.Source = CustomerContacts.CustomerContactPaged; GridCustomers.SelectionChanged += new SelectionChangedEventHandler(GridCustomers_SelectionChanged); BusyDialogIndicator.IsBusy = false; } void GridCustomers_SelectionChanged(object sender, SelectionChangedEventArgs e) { CustomerDetails.CurrentItem = GridCustomers.SelectedItem as CustomerContactLink; } private void SaveChanges_Click(object sender, RoutedEventArgs e) { if (WebContext.Current.User.IsAuthenticated) { bool commited = CustomerDetails.CommitEdit(); if (commited && (!CustomerDetails.IsItemChanged && CustomerDetails.IsItemValid)) { CustomerContacts.Update(CustomerDetails.CurrentItem as CustomerContactLink); CustomerContacts.ctx.SubmitChanges(); CustomerContacts.CustomerContactPaged.CommitEdit(); CustomerContacts.CustomerContactPaged.Refresh(); (GridCustomers.ItemsSource as PagedCollectionView).Refresh(); } } }

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• acl9 and devise don't seem to work well together

  - by Nik

  I have a user model which is access controlled by ACL9 in userscontroller: ACL9 related stuff before_filter :load_user, :only = [:show] access_control do allow :owner, :of = :user, :to = [:show] end def load_user user = User.find(params[:id]) end in ApplicaitonController I have a rescue_from 'Acl9::AccessDenied', :with = :access_denied def access_denied authenticate_user! # a method from Devise end it is no problem to type in url for sign in page http://localhost:3000/users/sign_in but it is a problem when for example I type in the user page first, which I am to expect to be redirected to sign in page automatically thru the logic above http://localhost:3000/users/1 #= infinite redirect hell. it tries to redirect back to users/1 again(!?) instead of directing to users/sign_in Does anyone have an opinion as to what might be going wrong? Thanks!

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• Scaffold default files are the best practice?

  - by antpaw

  Hey, i have some experience with MVC. but I'm new to rails. I'm using the scaffold command to generate some default files. The model looks clean and nice, but the controller and the views aren't really dry. The contents of new.html.erb and edit.html.erb are almost the same and the methods new/edit and create/update are doing almost the same thing. In other frameworks i've used only one view for updating and creating new entries and also the same method in my controller by setting the id as an optional parameter. Do they use this structure to keep things RESTful (i have not much of a clue about rest :()? Is it the best practice to use this default stuff for crud?

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• Multiple classes in a Python module

  - by ralphL

  I'm very new to Python (I'm coming from a JAVA background) and I'm wondering if anyone could help me with some of the Python standards. Is it a normal or "proper" practice to put multiple class in a module? I have been working with Django and started with the tutorials and they place their database model classes in the same module. Is this something that is normally done or should I stick with 1 class per module? Is their a reason I would do one over the other? Hope I'm being clear and not to generic. Thanks to everyone in advance!

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