entity-framework

问题 List<Post> list = ( from c in db.TitleComments join t in db.Titles on c.TitleId equals t.Id join u in db.Users on c.UserId equals u.Id where t.Id == _titleId && c.Date > time orderby c.Date descending select new Post { Username = u.Username, PostingDate = c.Date.ToString(), Data = c.Comment } ).ToList(); The code above causes exception on the convertion of date to string, PostingDate = c.Date.ToString(). Any ideas how to get around this? Exception error: {"LINQ to Entities does not recognize

问题 I have: Dictionary<int, List<int>> dict = new ... var a = SomeEntity.Where(f => dict[f.key].Contains(f.someValue)) this produces error LINQ to Entities does not recognize the method 'System.Collections.Generic.List`1[System.Int32] get_Item(Int32)' method while with lists it works: List<int> l = new ... var a = SomeEntity.Where(f => l.Contains(f.someValue)) So is this limitation of linq to EF or am I missing something? 回答1: It's the nature of Entity Framework - when you put expressions into

问题 List<Post> list = ( from c in db.TitleComments join t in db.Titles on c.TitleId equals t.Id join u in db.Users on c.UserId equals u.Id where t.Id == _titleId && c.Date > time orderby c.Date descending select new Post { Username = u.Username, PostingDate = c.Date.ToString(), Data = c.Comment } ).ToList(); The code above causes exception on the convertion of date to string, PostingDate = c.Date.ToString(). Any ideas how to get around this? Exception error: {"LINQ to Entities does not recognize

问题 I have a stored procedure in my Entity Data Model and added it to the function imports. Problem is... Visual Studio generates the function code in the model's code-behind if and only if I specify the return to be an entity type. Scalar and null return types do not work. Visual Studio does not generate the function code when I choose them. Is there something I am missing, or is this a bug? Any work-arounds? Using Visual Studio 2008 v9.0.30729.1 SP (Service Pack 1) 回答1: It's not so much a bug

问题 Frankly I am a newbie in both C# and Asp.net MVC. I also do not know how the asp.net web application actually works on IIS and ASP.NET framework behind the scene. I am confused with the decision where I have to declare a field of DbContext (or any class derived from DbContext) in my asp.net mvc application. I have two choices: Declare the field as a static field inside global.asax such that all controllers can make use of it. Declare the field as an instance field inside each controller class

问题 I can't figure out why I'm getting this error. I have used this function successfully with previous versions of Entity Framework but I've set up a new project using EF6 and it's not cooperating. using System.Data; using System.Data.Objects.SqlClient; e.Result = from n in MyDB.tblBulletins where n.AnncStart <= DateTime.Now && n.AnncEnd > DateTime.Now && n.Approved == true orderby n.AnncStart descending, n.AnncDate descending select new { n.RecID, AnncTitle = n.AnncTitle + " <a href=

问题 I can't figure out why I'm getting this error. I have used this function successfully with previous versions of Entity Framework but I've set up a new project using EF6 and it's not cooperating. using System.Data; using System.Data.Objects.SqlClient; e.Result = from n in MyDB.tblBulletins where n.AnncStart <= DateTime.Now && n.AnncEnd > DateTime.Now && n.Approved == true orderby n.AnncStart descending, n.AnncDate descending select new { n.RecID, AnncTitle = n.AnncTitle + " <a href=

问题 I know it has been asked before, but after long hours of searching and coding I can't get to a working and clean approach. Here is what I have: public class QuestionModel { public int QuestionID { get; set; } public string QuestionText { get; set; } public IList<QuestionChoiceModel> Choices { get; set; } } public class QuestionChoiceModel { public int ChoiceID { get; set; } public string ChoiceText { get; set; } } I'm using EF 5 for this ASP.Net MVC application. Generic Repository Pattern and

问题 I have classes like: Person { Name Address } Employee : Person { Compensation - object } Visitor : Person { } If I write linq: var persons = Context.Persons .Include("Compensation"); I get error: A specified Include path is not valid. The EntityType 'Person' does not declare a navigation property with the name 'Compensation'. It works ok if I do: var persons = Context.Persons .OfType<Employee>() .Include("Compensation"); But I would like to get Employees and visitors in the same query. Looks

问题 I have classes like: Person { Name Address } Employee : Person { Compensation - object } Visitor : Person { } If I write linq: var persons = Context.Persons .Include("Compensation"); I get error: A specified Include path is not valid. The EntityType 'Person' does not declare a navigation property with the name 'Compensation'. It works ok if I do: var persons = Context.Persons .OfType<Employee>() .Include("Compensation"); But I would like to get Employees and visitors in the same query. Looks