linq-to-sql

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

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

来源： https://stackoverflow.com/questions/51783974/group-child-records-by-parentid-and-sum-the-amount-linq-c-sharp

来源： https://stackoverflow.com/questions/51783974/group-child-records-by-parentid-and-sum-the-amount-linq-c-sharp

来源： https://stackoverflow.com/questions/13951061/how-to-insert-update-delete-records-from-tables-without-primary-key-using-linq

来源： https://stackoverflow.com/questions/13951061/how-to-insert-update-delete-records-from-tables-without-primary-key-using-linq

问题 I have the following query that receives a list of ints as a parameter: public int GetMostRecent(List<int> TheIDs) { ...using MyDC... var TheMostRecentID = (from d in MyDC.Data where TheIDs.Contains(d.ID) orderby d.DateTime select d.ID).LastOrDefault(); } Is this the best way to match a list within a parameter collection to data in the database or is there a better way than using the .Contains() method in linq-to-sql. Thanks. 回答1: What you have is correct. This will be translated into an IN

问题 I have a list of keywords in an ArrayList and I wanted to be able to build a query to find records in a table based on this keywords. Since the list of keywords is dynamic I cannot build a fixed query here. I do something like this: foreach (string kw in keywords) { query = query.Where(p => p.Name.StartsWith(kw)); } The "StartsWith" is required here because I need to search those records that actually start with the provided keyword. In T-SQL it Would be something like this Select * from

问题 I have a list of keywords in an ArrayList and I wanted to be able to build a query to find records in a table based on this keywords. Since the list of keywords is dynamic I cannot build a fixed query here. I do something like this: foreach (string kw in keywords) { query = query.Where(p => p.Name.StartsWith(kw)); } The "StartsWith" is required here because I need to search those records that actually start with the provided keyword. In T-SQL it Would be something like this Select * from

问题 I recently updated the project code into .NET Core 3.1 and EF Core 3.1, now most of my linq queries brake, EX. public override ICollection<ContactDetailModel> GetAll(ICollection<int> ids) { return _context .Set<TEntity>() .IgnoreDeletedEntities() .Where(x => ids.Distinct().Contains(x.ContactId)) .Select(EntityToDTOMapper) .ToList(); } This code throws an error where I use Contains, I saw in some other posts this issues has been fixed as a bug, but yet it fails. Error I get is "could not be