entity-framework-4

问题 I've been using Entity Framework Profiler to test my data access in an MVC project and have come accross several pages where I'm making far more db queries than I need to because of N+1 problems. Here is a simple example to show my problem: var club = this.ActiveClub; // ActiveClub uses code similar to context.Clubs.First() var members = club.Members.ToList(); return View("MembersWithAddress", members); The view loops through Members and then follows a navigion property on each member to also

问题 My solution is Silverlight which uses WCF RIA service SP1 and Entity Framework 4. I have a problem with loading large size data. I've got this error message. System.ServiceModel.DomainServices.Client.DomainException : Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. I think that it's a problem regards with timeout, so I tried below code. It worked when I hadn't install WCF Ria service "SP1". But it's not working since I've

问题 I'm running into a small problem where I'm trying to bind a DataTextColumn of a DataGrid to a Calculated Field. WPF <DataGrid ItemsSource="{Binding Path=CurrentRoster, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" AutoGenerateColumns="False" AlternatingRowBackground="Gainsboro" AlternationCount="2"> <DataGrid.Columns> <DataGridComboBoxColumn Header="Student Enrolled" ItemsSource="{Binding Source={StaticResource AvailableStudents}}" SelectedItemBinding="{Binding Path=Student}"> <

问题 Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None); config.ConnectionStrings.ConnectionStrings["MyConnectionString",String.Format("DataSource={0};")].ConnectionString=textBox1.Text; config.Save(ConfigurationSaveMode.Modified, true); ConfigurationManager.RefreshSection("connectionStrings"); I'm having trouble at line two. I cant seem to get the syntax correct. As you can see, i only want to update the DataSource value only. For example, if current

问题 I am using entity framework code first approach, and I am building a generic Repository class that provides data access. In this class I want an Add(T entity) method. However, there is no InsertOnSubmit method as part of the DbSet<T> class, and if I try to use the Add method, I get a compile time error: The type 'TEntity' must be a reference type in order to use it as parameter 'TEntity' in the generic type or method 'System.Data.Entity.DbContext.Set<TEntity>()' This is the method: public

问题 I have run into a scenario where Entity Framework 4.0 does not generate an association to an entity backed by a table having a unique index, and I am wondering why. The basic setup is this: Let's say I have two tables in SQL Server 2008 R2 and a foreign key relation: CREATE TABLE [dbo].[User]( [Id] [int] IDENTITY(1,1) NOT NULL, [GroupId] [int] NULL, CONSTRAINT [PK_User] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS

问题 We have an ASP.Net MVC3 application that is running on Azure, connecting to a Sql Azure Database via Entity Framework. The Developer that produced this has Pooling=False in the connection string. I would have thought this was a bad idea - wouldn't we want to re-use the connections if possible? Can anyone give me some guidance of when this might be a good idea? Thanks! 回答1: Yes, it is bad idea to have pooling=False. I don't use this option even for development. You should always use the SQL

问题 I think I'm going in circles. I'm working on an MVC 3 solution using EF4 & POCOs (database-first) and IoC. My repository and UoW patterns were mostly adopted from this article and this article. My solution is made up of the following projects: Implementations: Presentation (MVC site) Domain Services (business layer) Domain Repository (data access) Domain Context (my EF4 edmx and generated context) Domain Models (my EF4 generated POCOs) Interfaces: Domain Services Interfaces (business layer

问题 I have 1:N relationship between Program and Student tables which EF converted into navigation property. Now I want to delete all those records in this navigation students. I started like this: foreach(Student student in program.Students) program.Students.Remove(student); But I am a little bit skeptical about this. Than I tried this way: while (program.Students.Count > 0) program.Students.Remove(program.Students.ToList()[0]); But this seems weird too. Is there some simpler way to do this or if

问题 Hi I have a table Customer. One of the columns in table is DateCreated . This column is NOT NULL but default values is defined for this column in db. When I add new Customer using EF4 from my code. var customer = new Customer(); customer.CustomerName = "Hello"; customer.Email = "hello@ello.com"; // Watch out commented out. //customer.DateCreated = DateTime.Now; context.AddToCustomers(customer); context.SaveChanges(); Above code generates following query. exec sp_executesql N'insert [dbo].