I have a List and each Filter object has a property called "Id". I want to fetch all the records from my database using Linq to SQL that contains those ids. The List is not part of the database it is just an independent list.
not very clear question. however this is what, i suppose, u r trying to do
from c in datacontext.TableName where
IndependentList.Contains(c=>c.id)
select c
Related
I'm writing a timesheet application (Silverlight) and I'm completely stuck on getting linq queries working. I'm netw to linq and I just read, and did many examples from, a Linq book, including Linq to Objects, linq to SQl and linq to Entities.(I assume, but am not 100% sure that the latter is what Lightswitch uses). I plan to study a LOT more Linq, but just need to get this one query working.
So I have an entity called Items which lists every item in a job and it's serial no
So: Job.ID int, ID int, SerialNo long
I also have a Timesheets entity that contains shift dates, job no and start and end serial no produced
So Job.ID int, ShiftDate date, Shift int, StartNo long, EndNo long
When the user select a job from an autocomplete box, I want to look up the MAX(SerialNo) for that job in the timesheets entity. If that is null (i.e. none have been produced), I want to lookup the MIN(SerialNo) from the Items entity for that job (i.e. what's the first serial no they should produce)
I realize I need a first or default and need to specify the MIN(SerialNo) from Items as a default.
My Timesheet screen uses TimesheetProperty as it's datasource
I tried the following just to get the MAX(SerialNo) from Timesheets entity:
var maxSerialNo =
(from ts in this.DataWorkspace.SQLData.Timesheets
where ts.Job.ID == this.TimesheetProperty.Job.ID
select ts.StartNo).Min();
but I get the following errors:
Instance argument: cannot convert from 'Microsoft.LightSwitch.IDataServiceQueryable' to 'System.Collections.Generic.IEnumerable
'Microsoft.LightSwitch.IDataServiceQueryable' does not contain a definition for 'Min' and the best extension method overload 'System.Linq.Enumerable.Min(System.Collections.Generic.IEnumerable)' has some invalid arguments
I also don't get why I can't use this:
var maxSerialNo = this.DataWorkspace.SQLData.Timesheets.Min(ts => ts.StartNo);
Can anyone point me in the right direction?
Thanks
Mark
IDataServiceQueryable doesn't support full set of LINQ operator like IEnumerable has.
IDataServiceQueryable – This is a LightSwitch-specific type that allows a restricted set of “LINQ-like” operators that are remote-able to the middle-tier and ultimately issued to the database server. This interface is the core of the LightSwitch query programming model. IDataServiceQueryable has a member to execute the query, which returns results that are IEnumerable. [Reference]
Possible solution is, execute your query first to get collection of type IEnumerable by calling .ToList(), then you can call .Min() against the first query result. But that isn't good idea if you have large amount of data, because .ToList() will retrieve all data match the query and do further processing in client side, which is inefficient.
Another way is, change your query using only operators supported by IDataServiceQueryable to avoid retrieving unnecessary data to client. For example, to get minimum StartNo you can try to use orderby descending then get the first data instead of using .Min() operator :
var minStartNo =
(
from ts in this.DataWorkspace.SQLData.Timesheets
where ts.Job.ID == this.TimesheetProperty.Job.ID
orderby ts.StartNo descending select ts
).FirstOrDefault();
I need to support legacy client and compose ADO datasets from our Linq queries. The problem is how get specific column information (varchar length, decimal precision, etc) that cannot be obtained using reflection.
for example, I have table Customer with field Name varchar(80)
When I fetch data from linq to entities query:
var data = (from c in ctx.Customers select c.Name).ToList()
I cannot obtain maxSize for the column data[i].Name and adodataset raises an error.
I already have simple solution:
Code to extract column metadata from ObjectContext by property reference
Simple code that parses expression from Queryable and links output properties to edm columns.
But I have a lot of issues parsing complex queries that include multiple nested groupbys/unions/joins etc.
Does anybody know any other way (maybe using materialization shaper or similar)?
Thanks to EFProviderWrappers by Joseph Kowalski I have made similar provider and published it on codeplex
I have list A that has a lookup to list B that allows multiple entries. One A to multiple related Bs - standard practice. I want to find A where B contains a reference to a particular instance of 'b'.
I've tried:
var As = from a in ARecs where a.Bs.Contains(b) select a;
But I get the usual 'multiple tables involved' error. How do I go about this please?
thanks in advance
the error I'm getting is "The query uses unsupported elements, such as references to more than one list, or the projection of a complete entity by using EntityRef/EntitySet."
The A and B list code is generated by SPMetal if that makes any difference
Some LINQ cannot be turned into CAML (did I forget to mention this was on SPMetal generated LINQ to Sharepoint - doh!) and needs to be performed as 2 queries - the first ToList then the 2nd on that list. This worked for me.
Var Bs = A.ToList().Where(record => record.Bs.Contains(b))
Can anyone help me, to convert the below sql query to Linq (Lambda Expressions).
Thanks in Advance.
SQL Query:
UPDATE A INNER JOIN B ON (A.Trade Number=B.Trade Number) AND
(A.AccountId=B.AccountId) SET A.Float = B.CCY, A.Float = B.BASIS,
A.LastReset = B.FIXING, A.LastLibor = B.INTRATE;
Updates are not expressed as LINQ statements. You can use LINQ to load the record you wish to modify, but the actual update will involve a separate method call, the details of which will depend on which database technology you're using.
So, assuming you already have a reference to the record you wish to update from A, load the associated record from B (using LINQ), perform the updates to A programatically, and then save the changes to A.
Here's an example using LINQ-to-SQL.
So I'm extremely new to Linq in .Net 3.5 and have a question. I use to use a custom class that would handle the following results from a store procedure:
Set 1: ID Name Age
Set 2: ID Address City
Set 3: ID Product Price
With my custom class, I would have received back from the database a single DataSet with 3 DataTables inside of it with columns based on what was returned from the DB.
My question is how to I achive this with LINQ? I'm going to need to hit the database 1 time and return multiple sets with different types of data in it.
Also, how would I use LINQ to return a dynamic amount of sets depending on the parameters (could get 1 set back, could get N amount back)?
I've looked at this article, but didn't find anything explaining multiple sets (just a single set that could be dynamic or a single scalar value and a single set).
Any articles/comments will help.
Thanks
I believe this is what you're looking for
Linq to SQL Stored Procedures with Multiple Results - IMultipleResults
I'm not very familiar with LINQ myself but here is MSDN's site on LINQ Samples that might be able to help you out.
EDIT: I apologize, I somehow missed the title where you mentioned you wanted help using LINQ with Stored Procedures, my below answer does not address that at all and unfortunately I haven't had the need to use sprocs with LINQ so I'm unsure if my below answer will help.
LINQ to SQL is able hydrate multiple sets of data into a object graph while hitting the database once. However, I don't think LINQ is going to achieve what you ultimately want -- which as far as I can tell is a completely dynamic set of data that is defined outside of the query itself. Perhaps I am misunderstanding the question, maybe it would help if you provide some sample code that your existing application is using?
Here is a quick example of how I could hydrate a anonymous type with a single database call, maybe it will help:
var query = from p in db.Products
select new
{
Product = p,
NumberOfOrders = p.Orders.Count(),
LastOrderDate = p.Orders.OrderByDescending().Take(1).Select(o => o.OrderDate),
Orders = p.Orders
};