entity-framework-4

问题 Suppose I have a table with the column Description, varchar(100). If try to insert a string with more than 100 characters, the insert will fail. Is there a way in Entity Framework to automatically truncate or trim the string to fit into the column before inserting into the column? In my scenario, I really don't care whether the string is truncated, I just want it inserted rather than just failing and logging the rror. Since the model already knows the length limits, I was thinking there might

问题 I have a database and i using 2 different schemas. Schemas are like namespaces (correct me if i am wrong). This way i have 1 db and currently 2 schemas... so the tables in 1 schema can be named the same as the tables in the other schema because they are in separate schemas. How do i get EF Code first to talk to a different schema and not the default schema? Is it somethign to do with MapSingleType and overriding a method or can i do something else? ANy help really appreciated. 回答1: You can

问题 I have models based on EF Code First and I want to use them with the default MembershipProvider, but I don't know how to write the model correctly, so it won't erase all my data on recreating the tables when there were changes made to the model. 回答1: Currently (EF 4.1 CTP) EF Code First doesn't have that option. It always drops a table if you made changes to model. Update: EF 4.1 RTM allows you to create a custom database initializer and specify creation of db objects and data seeding. 回答2:

问题 I am doing some profiling on a WCF service that uses EF (System.Data.Entities) to read from a sql DB. When I spin up multiple parallel clients that hit the service, the CPUs all go to 100%, performance generally tanks, and everything bogs down. In profiling this with the concurrency profiler, I found 85% of the time is spent in synchronization, with only about 4% being actual code execution. Looking deeper into the stack trace, most of the synchronization seems to be from a call to

问题 In LINQ to SQL, I can create a repository dynamically using DataContext.GetTable<T> . Is there a similar way to do this in Entity Framework 4 other than declaring the properties on the specific DbContext ? For example: public MyDbContext: DbContext { public DbSet<MySet> MySets {get; set;} } I would like to know how can I create/get a reference to MySets dynamically as I can with LINQ to SQL as in: var mySet = MyDbContext.GetTable<MySet>(); 回答1: DbContext has method for this: var set = context

问题 from last 10 days I am trying many ways/example/tutorials which are provide in net to solve my problems. But, for all of those cases I fail down. I want to upload images for specific/multiple products, save them in database and display them in Home page by calling their ID . Can anyone give me step by step example/tutorials/link for this. Please don't give an partial answer/suggestion . Because I am already bore about those. 回答1: I just solved my Problems and here is the solution : This is my

问题 If model-first, we use [MetadataType(typeof(ConceptMetadataSource))] to attach a MetadataSource file which contains all the data annotations like [HiddenInput(DisplayValue = false)] or [Display(Name = "Title")] . For example: [MetadataType(typeof(ConceptMetadataSource))] public partial class Concept ... Now, I am using database-first approach since there is an existing database. This time, the entity classes are automatically created by edmx model. At the beginning of each entity class, there

问题 How do you represent a many-to-many relationship in the EF4 Code-First CTP3? For example if I have the following classes: class User { public int Id { get; set; } public string Name { get; set; } public ICollection<Profile> Profiles { get; set; } } class Profile { public int Id { get; set; } public string Name { get; set; } } In the database there is a UserProfiles table that has the FK for User and FK for Profile. How can I map this? EDIT: I understand how to to currently map with having a

问题 I have an entity, let's call it CommonEntity that has a primary key used as a foreign key in many other entities. As the application is developed these links will continue to grow. I'd like a way to see if CommonEntity can be safely deleted (i.e. it's not used by any other entities). I realise I can do if(!ce.EntityA.Any() && !ce.EntityB.Any() ... && !ce.EntityN.Any()) { //Delete } but I'm hoping for a way to just check all of the relationships automatically, as I don't love the idea of

问题 I have been struggling on executing EF Migrate.exe to work. My Solution has couple of projects. The migrations and the entities live in the project Data. The controllers and views live in Web. I tried using the migrate.exe - however I am struggling getting the first argument (assembly) to be accepted. Documentations says: Assembly: Specifies the name of the assembly that contains the migrations configuration type. I have tried: migrate.exe "MySolution\DataProject\bin\Debug\Data.dll" ERROR: