linq-to-entities

来源： https://stackoverflow.com/questions/12036377/how-to-use-and-operator-in-linq-join

来源： https://stackoverflow.com/questions/63991230/how-to-make-linq-join-work-if-one-of-the-fields-in-composite-key-is-nullable

来源： https://stackoverflow.com/questions/15566416/linq-to-entity-using-anonymous-object-in-a-query

问题 I have a problem converting simple linq query to Lambda Expression. My queries look like this: int[] array = List<int> array2 = sql.OfType<Table1>().Select(x=>x.ID).Take(10).ToList(); var result = sql.OfType<Table1>().Where(x => array.Contains(x.ID)).Take(10).ToList(); and the final result should be: static void DynamicSQLQuery<T>(IQueryable<T> sql, string fieldName) { List<int> array = sql.OfType<T>().Select(SelectExpression<T>(fieldName)).Take(10).ToList(); var result = sql.OfType<T>()

问题 I am trying to group join in EF core 3.1 the problem it returns Processing of the LINQ expression 'DbSet failed. This may indicate either a bug or a limitation in EF Core my code is like this var employees = await (from enrollment in RepositoryContext.Enrollments join allowance in RepositoryContext.Allowances.Include(y=>y.AllowanceType) on enrollment.EmployeeId equals allowance.EmployeeId into allowances select new { enrollment, allowances } ).AsNoTracking().ToListAsync(); the allowances is

问题 I am looking for some guidance/help on how to approach my problem as I'm running out of ideas. I am trying to take a custom extension function and pass it to the database via Entity Framework (EF Core 3.1) using Linq to Entities but I am getting a "{method} could not be translated" error regardless of what I do. I have tried using HasDbFunction along with HasTranslation using this link Thinktecture - Entity Framework Core - Custom Functions (using HasDbFunction) to no avail. I have also tried

问题 I have an entity with a foreign key relationship to an asp.net membership provider users table. This portion of the model looks like this: I can't seem to assign the foreign key relationship when inserting the Users table record, the record containing the foreign key to the aspnet_Users table. I keep getting the error: An item with the same key has already been added. The code I'm using looks like: UserAdmin userToAdd = new UserAdmin(); ... userToAdd.aspnet_Users = membershipUser; //line

问题 What could be causing this problem? public ActionResult Index(int page = 0) { const int pageSize = 3; var areas = repo.FindAllAreas(); var paginatedArea = new PaginatedList<Area>(areas, page, pageSize); return View(paginatedArea); } using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace UTEPSA.Controllers { class PaginatedList<T> : List<T> { public int PageIndex { get; private set; } public int PageSize { get; private set; } public int TotalCount { get

问题 I'm writing some LINQ to fetch records based on an email, however, the generated SQL contains an additional IS NULL condition which doesn't need to be there because I am checking the parameter value for null in the code prior to adding the condition to the query. My LINQ code is: if (email != null) { query = query.Where(r => r.Email == email); } The SQL condition generated from this is: (([Extent1].[Email] = @p__linq__0) OR (([Extent1].[Email] IS NULL) AND (@p__linq__0 IS NULL))) The ((

问题 I'm writing some LINQ to fetch records based on an email, however, the generated SQL contains an additional IS NULL condition which doesn't need to be there because I am checking the parameter value for null in the code prior to adding the condition to the query. My LINQ code is: if (email != null) { query = query.Where(r => r.Email == email); } The SQL condition generated from this is: (([Extent1].[Email] = @p__linq__0) OR (([Extent1].[Email] IS NULL) AND (@p__linq__0 IS NULL))) The ((