var query_actualizar = from x in ctx.banner
let orden = ctx.banner.Where(y.id_banner == id_banner).First(y=> y.orden)
where x.orden > orden
select x;
foreach (banner ord in query_actualizar)
{
ord.orden = ord.orden - 1;
}Good morning I would like to make a query in LINQ: SQL = > Update BANNER set ORDER = ORDER - 1 where ORDER > (select ORDER from BANNER where ID_BANNER = 18)
When making the query I get this error: 
The problem with your original query is that First what you expect is a conditional that meets the record you want to return. There are several options to do what you ask, one is:
var query_actualizar = from x in ctx.banner
let orden = ctx.banner.First(y=> y.id_banner == id_banner).orden
where x.orden > orden
select x;
Another
var query_actualizar = from x in ctx.banner
let orden = ctx.banner.Where(y.id_banner == id_banner).Select(y=>y.orden).FirstOrDefault();
where x.orden > orden
select x;
Right now I can not prove it, but I think either of you should work. If not, tell me about it.
I edit with the new information
Test using the FirstOrDefault method to get the first element of the sequence that meets the condition:
var query_actualizar = from x in ctx.banner
let orden = ctx.banner.FirstOrDefault(y => y.id_banner == id_banner).orden
where x.orden > orden
select x;
Hello, Santiaguito, test your code, and I got the following error, sent the image, please some idea of how to correct this ?, Thanks
Holas Pikoh and Santiaguito, I came out with this code, Gracias!.
var query_actualizar = from x in ctx.banner
let orden = ctx.banner.First(y=> y.id_banner == id_banner).orden
where x.orden > orden
select x;I think it would be convenient to first evaluate if the result of the query with firstordefault is different from null, before invoking the Where. Inside the library assembly. Indicates:
// Exceptions:
// System.ArgumentNullException:
// source or predicate is null.