entity-framework-4

问题 Situation: What I'd like to do is have access to the data context for the life cycle of a page. This is primarily to (a) avoid series of using() and to avoid (b) out of scope exceptions in the view when a lazy loaded property is accessed. Edit: I'm using MVC 4 and Entity Framework 4.3.1 (the latest) What I typically do is using (MyDB b = new MyDB()) { ...do all my stuff } In my controller or the data layer. The nice thing about this, based on my reading, is it's clean, causes no memory leaks

问题 I have a query hitting EF4 using STEs and I'm having an issue with user-defined sorting. In debugging this, I have removed the dynamic sorting and am hard-coding it and I still have the issue. If I swap/uncomment the var results = xxx lines in GetMyBusinesses() , my results are not sorted any differently - they are always sorting it ascendingly. FYI, Name is a varchar(200) field in SQL 2008 on my Business table. private IQueryable<Business> GetMyBusinesses(MyDBContext CurrentContext) { var

问题 I've looked at hundreds of similar questions on SO to the one asked, but haven't found my answer. If this has been asked before, please accept my apologies. I have a SQL database with a column of cities and a column of their states respectively. I use the Entity Framework as my DAL and in my BLL have lots of LINQ to format, move stuff, etc. I have on my UI a drop-down which currently accepts a ToList() from a method in my BLL and all works well, but I need to alter this method to return city

问题 I essentially have three tables with FK's Make MakeId MakeName Model ModelId ModelName MakeId (FK) Vehicle VehicleId DatePurchased ModelId (FK) I would like a navigation property from Vehicle to Make without modifying my database I tried: public class Make { public int MakeId {get;set;} <snip>...</snip> public virtual Vehicle Vehicles {get;set;} } <snip>Model</snip> public class Vehicle { public int VehicleId {get;set} <snip>...</snip> public virtual Make VehicleMake {get;set;} } public class

问题 I have sql query: FROM tbl_UploadFile AS AllFiles LEFT JOIN tbl_FirstFile AS firstFiles ON AllFiles.Guid=firstFiles.[FileId] LEFT JOIN tbl_SecondFile AS secondFiles ON AllFiles.Guid=secondFiles.[FileId] LEFT JOIN tbl_ThirdFile AS thirdFiles ON AllFiles.Guid=thirdFiles.[FileId] WHERE firstFiles.[FileId] is NULL AND secondFiles.[FileId] is NULL AND thirdFiles.[FileId] is NULL; This query return guid from tbl_UploadFile, if this guid doen't use on tbl_FirstFile, tbl_SecondFile and tbl_ThirdFile.

问题 I'm trying to convert an SQL query to Linq containing several left outer joins, but I'm encountering an odd situation. The relevant part of my SQL is: SELECT * FROM dbo.SessionDetails as sd left outer join dbo.VoipDetails as vd on vd.SessionIdTime = sd.SessionIdTime and vd.SessionIdSeq = sd.SessionIdSeq left outer join dbo.Gateways as fgw on vd.FromGatewayId = fgw.GatewayId My Linq query so far is: var query = from sd in dbo.SessionDetails join vd in dbo.VoipDetails on new { sd.SessionIdTime,

问题 I am creating a login screen where I get the user Id and password from the form .How do I use the entity framework to check if a duplicate id already exists in the database ? I am using entity framework 4 and asp.net 4.0 I am really new to the entity framework so a simple response would be very helpful. Thanks ! 回答1: Duplicate id? So do you want to validate that login is correct or do you want to check that login already exists during creating a new user? If you want to validate login use:

问题 I have an entity framework model, and I noticed that one table, a usergroup table is missing from the diagrams in the model file. This meant I could not modify it from the standard SQL calls to become part of the entity framework (i.e., to make a class file for it with entities). I can see it under "entity sets" but not in the diagram. Every time I try to add, it doesn't show it as an option to add in the "update model" menu. So I deleted it from Entity set, and then I finally saw it in

问题 I am attempting to create an ASP.NET MVC 3 application using C#, Entity Framework 4.0 code-first and SQL Server CE, and the automated scaffolding. Everything works fine until I try to actually use a page that connects to the SQL Server CE database. My connection in the web.config is this <add name="BRX" connectionString="Data Source=|DataDirectory|BRX.sdf" providerName="System.Data.SqlServerCe.4.0"/> My model class looks like this using System; using System.Collections.Generic; using System

问题 I have a simple Login page that suddenly (After upgrading Jquery.js and Jquery-ui.js to 1.10.2 and 1.10.3 respectively) started to actually reach the action result instead of showing the client side validation messages defined on the E.F Data Annotations. So I found out that removing the only CheckBoxFor that I have besides the User and Password, the submit button actually works as it should be so that it raises client validations only without reaching the controller. Any reason for this