linqkit

问题 I have the code: var predicate = PredicateBuilder.True<Value>(); predicate = predicate.And(x => x.value1 == "1"); predicate = predicate.And(x => x.value2 == "2"); var vals = Value.AsExpandable().Where(predicate).ToList(); If I have PredicateBuilder.True<Value>() , it brings back what I expect, but if I have PredicateBuilder.False<Value>() , it brings back 0 records. Can someone explain what the the difference is and why in one scenario I get back 0 records an in the other I get what I expect.

问题 I have the code: var predicate = PredicateBuilder.True<Value>(); predicate = predicate.And(x => x.value1 == "1"); predicate = predicate.And(x => x.value2 == "2"); var vals = Value.AsExpandable().Where(predicate).ToList(); If I have PredicateBuilder.True<Value>() , it brings back what I expect, but if I have PredicateBuilder.False<Value>() , it brings back 0 records. Can someone explain what the the difference is and why in one scenario I get back 0 records an in the other I get what I expect.

问题 I want to use LinqKit's PredicateBuilder and pass the predicate into .Any method for related model. So I want to build a predicate: var castCondition = PredicateBuilder.New<CastInfo>(true); if (movies != null && movies.Length > 0) { castCondition = castCondition.And(c => movies.Contains(c.MovieId)); } if (roleType > 0) { castCondition = castCondition.And(c => c.RoleId == roleType); } And then use it to filter model that has relation to model in predicate: IQueryable<Name> result = _context

问题 I'm using LinqKit library which allows combining expressions on the fly. This is a pure bliss for writing Entity Framewok data acess layer because several expressions can optionally be reused and combined, which allows both for readable and efficient code. Consider following piece of code: private static readonly Expression<Func<Message, int, MessageView>> _selectMessageViewExpr = ( Message msg, int requestingUserId ) => new MessageView { MessageID = msg.ID, RequestingUserID =

问题 Code: public static GetRows() { var to_ret = db.TableRows.Select(x=> new TableRowModel( { TableRowId = x.TableRowId, Type = x.Type, Name = x.Name, CreatedAt = x.CreatedAt, ModifiedAt = x.ModifiedAt, Enums = x.Enums.AsExpandable().Select(y => y.ToEnumModel()) }); return to_ret; } public static EnumModel ToEnumModel(this Enum x) { var to_ret = new EnumModel() { CFPId = x.CFPId, CreatedAt = x.CreatedAt, ModifiedAt = x.ModifiedAt, }; return to_ret; } Running GetRows gives error saying: LINQ to

问题 If I want retrieve more columns with an already existing lambda tree expression like below, how would I do that? This works with Entity Frameworks and want it to still work. Expression<Func<DivisionTeam, DirectorTeamModel>> columns= (d) => new DirectorTeamModel { Id = d.Id, TeamId = d.Team.Id }; if (criteria.Template == ExportTemplate.Import || criteria.Template == ExportTemplate.Default) { // Retrieve additional columns from "columns" expression tree } return _divisionTeamsRepository

问题 Let's say I have defined the following variables: IQueryable<MyClass> myQueryable; Dictionary<string, Expression<Func<MyClass, bool>>> extraFields; // the dictionary is keyed by a field name Now, I want to tack on some dynamic fields to the IQueryable, so that it returns an IQueryable<ExtendedMyClass> , where ExtendedMyClass is defined as: class ExtendedMyClass { public MyClass MyObject {get; set;} public IEnumerable<StringAndBool> ExtraFieldValues {get; set;} } class StringAndBool { public

问题 Given a simple parent/child class structure. I want to use linqkit to apply a child lambda expression on the parent. I also want the Lambda expression to be provided by a utility method. public class Foo { public Bar Bar { get; set; } } public class Bar { public string Value { get; set; } public static Expression<Func<Bar, bool>> GetLambdaX() { return c => c.Value == "A"; } } ... Expression<Func<Foo, bool>> lx = c => Bar.GetLambdaX().Invoke(c.Bar); Console.WriteLine(lx.Expand()); The above

问题 I'm using LINQ to Entities for Entity Framework objects in my Data Access Layer. My goal is to filter as much as I can from the database, without applying filtering logic to in-memory results. For that purpose Business Logic Layer passes a predicate to Data Access Layer. I mean Func<MyEntity, bool> So, if I use this predicate directly, like public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.Where(x => isMatched(x)); } I'm

问题 I am experiencing a problem while attempting to execute a query that I have built dynamically using PredicateBuilder. I am able to build the query but when executing the query itself I get the following "TypeLoadException"... When running: return context.SearchRecords.AsExpandable().Where(predicate).ToList(); Could not load type 'System.Data.Entity.Infrastructure.IDbAsyncEnumerable`1' from assembly 'EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. I have