linq-to-sql – Page 14

how to update the multiple rows at a time using linq to sql?

January 2, 2023 by Tarik

To update one column here are some syntax options: Option 1 var ls=new int[]{2,3,4}; using (var db=new SomeDatabaseContext()) { var some= db.SomeTable.Where(x=>ls.Contains(x.friendid)).ToList(); some.ForEach(a=>a.status=true); db.SubmitChanges(); } Option 2 using (var db=new SomeDatabaseContext()) { db.SomeTable .Where(x=>ls.Contains(x.friendid)) .ToList() .ForEach(a=>a.status=true); db.SubmitChanges(); } Option 3 using (var db=new SomeDatabaseContext()) { foreach (var some in db.SomeTable.Where(x=>ls.Contains(x.friendid)).ToList()) { some.status=true; } db.SubmitChanges(); } … Read more

A dependent property in a ReferentialConstraint is mapped to a store-generated column

December 30, 2022 by Tarik

Is it possible that you defined a bad column relation between your tables? In my case, I had different columns and one was set as autonumeric.

Linq to SQL how to do “where [column] in (list of values)”

December 30, 2022 by Tarik

Use where list.Contains(item.Property) Or in your case: var foo = from codeData in channel.AsQueryable<CodeData>() where codeIDs.Contains(codeData.CodeId) select codeData; But you might as well do that in dot notation: var foo = channel.AsQueryable<CodeData>() .Where(codeData => codeIDs.Contains(codeData.CodeId));

Random row from Linq to Sql

December 24, 2022 by Tarik

You can do this at the database, by using a fake UDF; in a partial class, add a method to the data context: partial class MyDataContext { [Function(Name=”NEWID”, IsComposable=true)] public Guid Random() { // to prove not used by our C# code… throw new NotImplementedException(); } } Then just order by ctx.Random(); this will do … Read more

NHibernate vs LINQ to SQL

December 23, 2022 by Tarik

LINQ to SQL forces you to use the table-per-class pattern. The benefits of using this pattern are that it’s quick and easy to implement and it takes very little effort to get your domain running based on an existing database structure. For simple applications, this is perfectly acceptable (and oftentimes even preferable), but for more … Read more

efficient way to implement paging

December 20, 2022 by Tarik

Trying to give you a brief answer to your doubt, if you execute the skip(n).take(m) methods on linq (with SQL 2005 / 2008 as database server) your query will be using the Select ROW_NUMBER() Over … statement, with is somehow direct paging in the SQL engine. Giving you an example, I have a db table … Read more

How to select only the records with the highest date in LINQ

December 16, 2022 by Tarik

If you just want the last date for each account, you’d use this: var q = from n in table group n by n.AccountId into g select new {AccountId = g.Key, Date = g.Max(t=>t.Date)}; If you want the whole record: var q = from n in table group n by n.AccountId into g select g.OrderByDescending(t=>t.Date).FirstOrDefault();

Linq: adding conditions to the where clause conditionally

December 11, 2022 by Tarik

If you do not call ToList() and your final mapping to the DTO type, you can add Where clauses as you go, and build the results at the end: var query = from u in DataContext.Users where u.Division == strUserDiv && u.Age > 18 && u.Height > strHeightinFeet select u; if (useAge) query = query.Where(u … Read more

How do you perform a CROSS JOIN with LINQ to SQL?

December 9, 2022 by Tarik

A cross-join is simply the Cartesian product of two sets. There’s no explicit join operator for it. var combo = from p in people from c in cars select new { p.Name, c.Make, c.Model, c.Colour };

LINQ to SQL Left Outer Join

November 22, 2022 by Tarik

You don’t need the into statements: var query = from customer in dc.Customers from order in dc.Orders .Where(o => customer.CustomerId == o.CustomerId) .DefaultIfEmpty() select new { Customer = customer, Order = order } //Order will be null if the left join is null And yes, the query above does indeed create a LEFT OUTER join. … Read more