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  • populating object collection property with Linq

    - by Benjamin Ortuzar
    I have an XML structure that has many doc nodes, and each node may have zero or more extract paragraphs (paras). <doc> <docitem>3</docitem> <docid>129826</docid> <doctitle>sample title</doctitle> <docdatetime>2009-07-03T16:59:00</docdatetime> <collectdatetime>2009-07-03T16:59:23</collectdatetime> <summary> <summarytext>sample summary</summarytext> </summary> <paras> <paraitemcount>2</paraitemcount> <para> <paraitem>1</paraitem> <paratext>sample text 1</paratext> </para> <para> <paraitem>2</paraitem> <paratext>sample text 2</paratext> </para> </paras> </doc> <doc> ... </doc> I also has some Linq code to populate some Document objects: List<Document> documentsList = (from doc in xmlDocument.Descendants("doc") select new Document { DocId = doc.Element("docid").Value, DocTitle = doc.Element("doctitle").Value, DocDateTime = DateTime.Parse(doc.Element("docdate").Value), DocSummary = doc.Element("summary").Value, DocParas = "" ///missing code to populate List<string> } ).ToList<Document>(); Is it possible add all the paras nodes into the Document.DocParas List<string> using Linq and Xpath, or should I do this task in a different way? Note: I'm using .NET C# 3.5

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  • Create System.Data.Linq.Table in Code for Testing

    - by S. DePouw
    I have an adapter class for Linq-to-Sql: public interface IAdapter : IDisposable { Table<Data.User> Activities { get; } } Data.User is an object defined by Linq-to-Sql pointing to the User table in persistence. The implementation for this is as follows: public class Adapter : IAdapter { private readonly SecretDataContext _context = new SecretDataContext(); public void Dispose() { _context.Dispose(); } public Table<Data.User> Users { get { return _context.Users; } } } This makes mocking the persistence layer easy in unit testing, as I can just return whatever collection of data I want for Users (Rhino.Mocks): Expect.Call(_adapter.Users).Return(users); The problem is that I cannot create the object 'users' since the constructors are not accessible and the class Table is sealed. One option I tried is to just make IAdapter return IEnumerable or IQueryable, but the problem there is that I then do not have access to the methods ITable provides (e.g. InsertOnSubmit()). Is there a way I can create the fake Table in the unit test scenario so that I may be a happy TDD developer?

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  • Beginner LINQ to XML inline XML error

    - by Kyle B.
    Imports System.Xml.Linq Imports System.Linq Partial Class test2 Inherits System.Web.UI.Page Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load Dim xml As XElement = <book> <title>My Title</title> <author>Kyle</author> <publisher>WROX</publisher> </book> End Sub End Class The above code is producing the following error: Compiler Error Message: BC30201: Expression expected. Source Error: Line 8: Line 9: Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load Line 10: Dim xml As XElement = <book> Line 11: <title>My Title</title> Line 12: <author>Kyle</author> Source File: C:\Inetpub\wwwroot\myproject\web\test2.aspx.vb Line: 10 Why? edit: Dim xml As XElement = New XElement("book", _ New XElement("title", "My Title"), _ New XElement("author", "Kyle"), _ New XElement("publisher", "WROX") _ ) The above code works, but obviously is not as elegant as the original and I would still appreciate an explanation of why my original syntax is wrong.

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  • Linq-To-Entities group by

    - by Oskar Kjellin
    Hey, I'm building a software for timereporting I have a Dictionary<string, Dictionary<string, double>>. The key in the main dictionary is a users name and their value is a dictionary of . I have a function GetDepartment(string UserName) which returns a string with the users department. What I want is to crate a new dictionary, of the same type, that has the department as the main key and in the subdictionary a where hours is the total for that department. I have been trying to do this with linq but did not succeed. Would be very glad for some help here! EDIT: This code does exactly what I want. But I want it in LINQ Dictionary<string, Dictionary<string, double>> temphours = new Dictionary<string, Dictionary<string, double>>(); ; foreach (var user in hours) { string department = GetDepartment(user.Key); if (!temphours.ContainsKey(department)) { temphours.Add(department, new Dictionary<string, double>()); } foreach (var customerReport in user.Value) { if (!temphours[department].ContainsKey(customerReport.Key)) { temphours[department].Add(customerReport.Key, 0); } temphours[department][customerReport.Key] += customerReport.Value; } }

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  • Linq to SQL case sensitivity causing problems

    - by Roger Lipscombe
    I've seen this question, but that's asking for case-insensitive comparisons when the database is case-sensitive. I'm having a problem with the exact opposite. I'm using SQL Server 2005, my database collation is set to Latin1_General_CI_AS. I've got a table, "User", like this: CREATE TABLE [dbo].[User] ( [Id] [int] IDENTITY(1,1) NOT NULL, [Name] [nvarchar](max) NOT NULL, CONSTRAINT [PK_Example] PRIMARY KEY CLUSTERED ( [Id] ASC ) ) And I'm using the following code to populate it: string[] names = new[] { "Bob", "bob", "BoB" }; using (MyDataContext dataContext = new AppCompatDataContext()) { foreach (var name in names) { string s = name; if (dataContext.Users.SingleOrDefault(u => u.Name == s) == null) dataContext.Users.InsertOnSubmit(new User { Name = name }); } dataContext.SubmitChanges(); } When I run this the first time, I end up with "Bob", "bob" and "BoB" in the table. When I run it again, I get an InvalidOperationException: "Sequence contains more than one element", because the query against the database returns all 3 rows, and... SELECT * FROM [User] WHERE Name = 'bob' ... is case-insensitive. That is: when I'm inserting rows, Linq to SQL appears to use C# case-sensitive comparisons. When I query later, Linq to SQL uses SQL Server case-insensitive comparisons. I'd like the initial insert to use case-insensitive comparisons, but when I change the code as follows... if (dataContext.Users.SingleOrDefault(u => u.Name.Equals(s, StringComparison.InvariantCultureIgnoreCase) ) == null) ... I get a NotSupportedException: "Method 'Boolean Equals(System.String, System.StringComparison)' has no supported translation to SQL." Question: how do I get the initial insert to be case-insensitive or, more precisely, match the collation of the column in the database? Update: This doesn't appear to be my problem. My problem appears to be that SingleOrDefault doesn't actually look at the pending inserts at all.

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  • SQL Query Not Functioning - No Error Message

    - by gamerzfuse
    // Write the data to the database $query = "INSERT INTO staff (name, lastname, username, password, position, department, birthmonth, birthday, birthyear, location, phone, email, street, city, state, country, zip, tags, photo) VALUES ('$name', '$lastname', '$username', '$password', '$position', '$department', '$birthmonth', '$birthday', '$birthyear', '$location', '$phone', '$email', '$street', '$city', '$state', '$country', '$zip', '$tags', '$photo')"; mysql_query($query); var_dump($query); echo '<p>' . $name . ' has been added to the Employee Directory.</p>'; if (!$query) { die('Invalid query: ' . mysql_error()); } Can someone tell me why the above code produced: string(332) "INSERT INTO staff (name, lastname, username, password, position, department, birthmonth, birthday, birthyear, location, phone, email, street, city, state, country, zip, tags, photo) VALUES ('Craig', 'Hooghiem', 'sdf', 'sdf', 'sdf', 'sdf', '01', '01', 'sdf', 'sdf', '', 'sdf', 'sdf', 'sd', 'sdf', 'sdf', 'sd', 'sdg', 'leftround.gif')" Craig has been added to the Employee Directory. But does not actually add anything into the database table "staff" ? I must be missing something obvious here.

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  • java: decoding URI query string

    - by Jason S
    I need to decode a URI that contains a query string; expected input/output behavior is something like the following: abstract class URIParser { /** example input: * something?alias=pos&FirstName=Foo+A%26B%3DC&LastName=Bar */ URIParser(String input) { ... } /** should return "something" for the example input */ public String getPath(); /** should return a map * {alias: "pos", FirstName: "Foo+A&B=C", LastName: "Bar"} */ public Map<String,String> getQuery(); } I've tried using java.net.URI, but it seems to decode the query string so in the above example I'm left with "alias=pos&FirstName=Foo+A&B=C&LastName=Bar" so there is ambiguity whether a "&" is a query separator or is a character in a query component. edit: just tried URI.getRawQuery() and it doesn't do the encoding, so I can split the query string with a "&", but then what do I do? Any suggestions?

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  • Databinding question: DataGridView <=> XDocument (using LINQ-to-XML)

    - by Pretzel
    Learning LINQ has been a lot of fun so far, but despite reading a couple books and a bunch of online resources on the topic, I still feel like a total n00b. Recently, I just learned that if my query returns an Anonymous type, the DataGridView I'm populating will be ReadOnly (because, apparently Anonymous types are ReadOnly.) Right now, I'm trying to figure out the easiest way to: Get a subset of data from an XML file into a DataGridView, Allow the user to edit said data, Stick the changed data back into the XML file. So far I have Steps 1 and 2 figured out: public class Container { public string Id { get; set; } public string Barcode { get; set; } public float Quantity { get; set; } } // For use with the Distinct() operator public class ContainerComparer : IEqualityComparer<Container> { public bool Equals(Container x, Container y) { return x.Id == y.Id; } public int GetHashCode(Container obj) { return obj.Id.GetHashCode(); } } var barcodes = (from src in xmldoc.Descendants("Container") where src.Descendants().Count() > 0 select new Container { Id = (string)src.Element("Id"), Barcode = (string)src.Element("Barcode"), Quantity = float.Parse((string)src.Element("Quantity").Attribute("value")) }).Distinct(new ContainerComparer()); dataGridView1.DataSource = barcodes.ToList(); This works great at getting the data I want from the XML into the DataGridView so that the user has a way to manipulate the values. Upon doing a Step-thru trace of my code, I'm finding that the changes to the values made in DataGridView are not bound to the XDocument object and as such, do not propagate back. How do we take care of Step 3? (getting the data back to the XML) Is it possible to Bind the XML directly to the DataGridView? Or do I have to write another LINQ statement to get the data from the DGV back to the XDocument? Suggstions?

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  • LINQ Normalizing data

    - by Brennan Mann
    I am using an OMS that stores up to three line items per record in the database. Below is an example of an order containing five line items. Order Header Order Detail Prod 1 Prod 2 Prod 3 Order Detail Prod 4 Prod 5 One order header record and two detail records. My goal is have a one to one relation for details records(i.e., one detail record per line item). In the past, I used an UNION ALL SQL statement to extract the data. Is there a better approcach to this problem using LINQ? Below is my first attempt at using LINQ. Any feedback, suggestions or recommendations would greatly be appreciated. For what I have read, an UNION statement can tax the process? var orderdetail = (from o in context.ORDERSUBHEADs select new { edpNo = o.EDPNOS_001, price = o.EXTPRICES_001, qty = o.ITEMQTYS_001 } ).Union(from o in context.ORDERSUBHEADs select new { edpNo = o.EDPNOS_002, price = o.EXTPRICES_002, qty = o.ITEMQTYS_002 } ).Union(from o in context.ORDERSUBHEADs select new { edpNo = o.EDPNOS_003, price = o.EXTPRICES_003, qty = o.ITEMQTYS_003 });

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  • Dynamic Linq Property Converting to Sql

    - by Matthew Hood
    I am trying to understand dynamic linq and expression trees. Very basically trying to do an equals supplying the column and value as strings. Here is what I have so far private IQueryable<tblTest> filterTest(string column, string value) { TestDataContext db = new TestDataContext(); // The IQueryable data to query. IQueryable<tblTest> queryableData = db.tblTests.AsQueryable(); // Compose the expression tree that represents the parameter to the predicate. ParameterExpression pe = Expression.Parameter(typeof(tblTest), "item"); Expression left = Expression.Property(pe, column); Expression right = Expression.Constant(value); Expression e1 = Expression.Equal(left, right); MethodCallExpression whereCallExpression = Expression.Call( typeof(Queryable), "Where", new Type[] { queryableData.ElementType }, queryableData.Expression, Expression.Lambda<Func<tblTest, bool>>(e1, new ParameterExpression[] { pe })); // Create an executable query from the expression tree. IQueryable<tblTest> results = queryableData.Provider.CreateQuery<tblTest>(whereCallExpression); return results; } That works fine for columns in the DB. But fails for properties in my code eg public partial class tblTest { public string name_test { get { return name; } } } Giving an error cannot be that it cannot be converted into SQL. I have tried rewriting the property as a Expression<Func but with no luck, how can I convert simple properties so they can be used with linq in this dynamic way? Many Thanks

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  • MsSQL 2005 query performance

    - by Max
    I have the following query: select ............. from //one table and about 20 left joins// where ( ( this_.driverName like 'blah*' or this_.renterName like 'blah*' ) or exists ( select this0__.id as y0_ from ThirdParty this0__ where this0__.name like 'blah*' and this0__.claim_id=this_.id ) ) order by this_.id asc And I have two environment: One with 175 000 records in table "this_" and second with 25 000 records in table "this_". This query works right on 175k database and it works smth about 2 seconds, but on base with 25k this query freezes. and if drop one the folloing item from where clause: ( this_.driverName like 'blah*' or this_.renterName like 'blah*' ) or exists ( select this0__.id as y0_ from ThirdParty this0__ where this0__.name like 'blah*' and this0__.claim_id=this_.id ) query runs normally. How can I to increase performance of this query?

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  • List Manipulation in C# using Linq

    - by Learner
    using System; using System.Collections.Generic; using System.Linq; using System.Linq.Expressions; using System.Text; namespace ConsoleApplication1 { public class Class1 { static void Main(string[] args) { List<Car> mylist = new List<Car>(); Car car1; Car car2; Car car3; car1 = new Car() { make = "Honda", id = 1 }; car2 = new Car() { make = "toyota", id = 2 }; car3 = new Car() { make = "Honda", id = 3, color = "red" }; mylist.Add(car1); mylist.Add(car2); **////mylist.Where(p => p.id == 1).SingleOrDefault() = car3;** } } public class Car { public int id { get; set; } public string make { get; set; } public string color { get; set; } } } How can I update the list by replacing the honda car of Id 1 with honda car with Id 3 in the best way.

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  • Creating LINQ to SQL Data Models' Data Contexts with ASP.NET MVC

    - by Maxim Z.
    I'm just getting started with ASP.NET MVC, mostly by reading ScottGu's tutorial. To create my database connections, I followed the steps he outlined, which were to create a LINQ-to-SQL dbml model, add in the database tables through the Server Explorer, and finally to create a DataContext class. That last part is the part I'm stuck on. In this class, I'm trying to create methods that work around the exposed data. Following the example in the tutorial, I created this: using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace MySite.Models { public partial class MyDataContext { public List<Post> GetPosts() { return Posts.ToList(); } public Post GetPostById(int id) { return Posts.Single(p => p.ID == id); } } } As you can see, I'm trying to use my Post data table. However, it doesn't recognize the "Posts" part of my code. What am I doing wrong? I have a feeling that my problem is related to my not adding the data tables correctly, but I'm not sure. Thanks in advance.

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  • Linq join two dictionaries using a common key

    - by rboarman
    Hello, I am trying to join two Dictionary collections together based on a common lookup value. var idList = new Dictionary<int, int>(); idList.Add(1, 1); idList.Add(3, 3); idList.Add(5, 5); var lookupList = new Dictionary<int, int>(); lookupList.Add(1, 1000); lookupList.Add(2, 1001); lookupList.Add(3, 1002); lookupList.Add(4, 1003); lookupList.Add(5, 1004); lookupList.Add(6, 1005); lookupList.Add(7, 1006); // Something like this: var q = from id in idList.Keys join entry in lookupList on entry.Key equals id select entry.Value; The Linq statement above is only an example and does not compile. For each entry in the idList, pull the value from the lookupList based on matching Keys. The result should be a list of Values from lookupList (1000, 1002, 1004). What’s the easiest way to do this using Linq? Thank you, Rick

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  • Sending items in a LINQ sequence to a method that returns void

    - by generalt
    Hello all. Often while I'm dealing with LINQ sequences, I want to send each item to a method returning void, avoiding a foreach loop. However, I haven't found an elegant way to do this. Today, I wrote the following code: private StreamWriter _sw; private void streamToFile(List<ErrorEntry> errors) { if (_sw == null) { _sw = new StreamWriter(Path.Combine (Path.GetDirectoryName(_targetDatabasePath), "errors.txt")); } Func<ErrorEntry, bool> writeSelector = (e) => { _sw.WriteLine(getTabDelimititedLine(e)); return true; }; errors.Select(writeSelector); _sw.Flush(); } As you can see, I write a lambda function that just returns true, and I realize that the Select method will return a sequence of booleans- I'll just ignore that sequence. However, this seems a little bit noobish and jank. Is there any elegant way to do this? Or am I just misapplying LINQ? Thanks.

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  • How do I setup Linq to SQL and WCF

    - by Jisaak
    So I'm venturing out into the world of Linq and WCF web services and I can't seem to make the magic happen. I have a VERY basic WCF web service going and I can get my old SqlConnection calls to work and return a DataSet. But I can't/don't know how to get the Linq to SQL queries to work. I'm guessing it might be a permissions problem since I need to connect to the SQL Database with a specific set of credentials but I don't know how I can test if that is the issue. I've tried using both of these connection strings and neither seem to give me a different result. <add name="GeoDataConnectionString" connectionString="Data Source=SQLSERVER;Initial Catalog=GeoData;Integrated Security=True" providerName="System.Data.SqlClient" /> <add name="GeoDataConnectionString" connectionString="Data Source=SQLSERVER;Initial Catalog=GeoData;User ID=domain\userName; Password=blahblah; Trusted_Connection=true" providerName="System.Data.SqlClient" /> Here is the function in my service that does the query and I have the interface add the [OperationContract] public string GetCity(int cityId) { GeoDataContext db = new GeoDataContext(); var city = from c in db.Cities where c.CITY_ID == 30429 select c.DESCRIPTION; return city.ToString(); } The GeoData.dbml only has one simple table in it with a list of city id's and city names. I have also changed the "Serialization Mode" on the DataContext to "Unidirectional" which from what I've read needs to be done for WCF. When I run the service I get this as the return: SELECT [t0].[DESCRIPTION] FROM [dbo].[Cities] AS [t0] WHERE [t0].[CITY_ID] = @p0 Dang, so as I'm writing this I realize that maybe my query is all messed up?

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  • Where Not In OR Except simulation of SQL in LINQ to Objects

    - by Thinking
    Suppose I have two lists that holds the list of source file names and destination file names respectively. The Sourcefilenamelist has files as 1.txt, 2.txt,3.txt, 4.txt while the Destinaitonlist has 1.txt,2.txt. I ned to write a linq query to find out which files are in SourceList that are absent in DestinationFile list. e.g. here the out put will be 3.txt and 4.txt. I have done this by a foreach statement. but now I want to do the same by using LINQ(C#). Edit: My Code is List<FileList> sourceFileNames = new List<FileList>(); sourceFileNames.Add(new FileList { fileNames = "1.txt" }); sourceFileNames.Add(new FileList { fileNames = "2.txt" }); sourceFileNames.Add(new FileList { fileNames = "3.txt" }); sourceFileNames.Add(new FileList { fileNames = "4.txt" }); List<FileList> destinationFileNames = new List<FileList>(); destinationFileNames.Add(new FileList { fileNames = "1.txt" }); destinationFileNames.Add(new FileList { fileNames = "2.txt" }); IEnumerable<FileList> except = sourceFileNames.Except(destinationFileNames); And Filelist is a simple class with only one property fileNames of type string.

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  • PDO update query with conditional?

    - by dmontain
    I have a PDO mysql that updates 3 fields. $update = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2, field3=:field3 WHERE key=:key"); But I want field3 to be updated only when $update3 = true; (meaning that the update of field3 is controlled by a conditional statement) Is this possible to accomplish with a single query? I could do it with 2 queries where I update field1 and field2 then check the boolean and update field3 if needed in a separate query. //run this query to update only fields 1 and 2 $update_part1 = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2 WHERE key=:key"); //if field3 should be update, run a separate query to update it separately if ($update3){ $update_part2 = $mypdo->prepare("UPDATE tablename SET field3=:field3 WHERE key=:key"); } But hopefully there is a way to accomplish this in 1 query?

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  • MySQL query killing my server

    - by Webnet
    Looking at this query there's got to be something bogging it down that I'm not noticing. I ran it for 7 minutes and it only updated 2 rows. //set product count for makes $tru->query->run(array( 'name' => 'get-make-list', 'sql' => 'SELECT id, name FROM vehicle_make', 'connection' => 'core' )); while($tempMake = $tru->query->getArray('get-make-list')) { $tru->query->run(array( 'name' => 'update-product-count', 'sql' => 'UPDATE vehicle_make SET product_count = ( SELECT COUNT(product_id) FROM taxonomy_master WHERE v_id IN ( SELECT id FROM vehicle_catalog WHERE make_id = '.$tempMake['id'].' ) ) WHERE id = '.$tempMake['id'], 'connection' => 'core' )); } I'm sure this query can be optimized to perform better, but I can't think of how to do it. vehicle_make = 45 rows taxonomy_master = 11,223 rows vehicle_catalog = 5,108 rows All tables have appropriate indexes

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  • Linq to sql Repository pattern , Some doubts

    - by MindlessProgrammer
    I am using repository pattern with linq to sql, I am using a repository class per table. I want to know , am i doing at good/standard way, ContactRepository Contact GetByID() Contact GetAll() COntactTagRepository List<ContactTag> Get(long contactID) List<ContactTag> GetAll() List<ContactTagDetail> GetAllDetails() class ContactTagDetail { public Contact Contact {get;set;} public ContactTag COntactTag {get;set;} } When i need a contact i call method in contactrepository, same for contacttag but when i need contact and tags together i call GetDetais() in ContactTag repository its not returning the COntactTag entity generated by the orm insted its returning ContactTagDetail entity conatining both COntact and COntactTag generated by the orm, i know i can simple call GetAll in COntactTag repository and can access Contact.ContactTag but as its linq to sql it will there is no option to Deferred Load in query level, so whenever i need a entity with a related entity i create a projection class Another doubt is where i really need to right the method i can do it in both contact & ContactTag repostitory like In contact repository GetALlWithTags() or something but i am doing it in in COntactTag repository Whats your suggestions ?

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  • DataReader already open when using LINQ

    - by Jamie Dixon
    I've got a static class containing a static field which makes reference to a wrapper object of a DataContext. The DataContext is basically generated by Visual Studio when we created a dbml file & contains methods for each of the stored procedures we have in the DB. Our class basically has a bunch of static methods that fire off each of these stored proc methods & then returns an array based on a LINQ query. Example: public static TwoFieldBarData[] GetAgesReportData(string pct) { return DataContext .BreakdownOfUsersByAge(Constants.USER_MEDICAL_PROFILE_KEY, pct) .Select(x => new TwoFieldBarData(x.DisplayName, x.LeftValue, x.RightValue, x.TotalCount)) .ToArray(); } Every now and then, we get the following error: There is already an open DataReader associated with this Command which must be closed firs This is happening intermittently and I'm curious as to what is going on. My guess is that when there's some lag between one method executing and the next one firing, it's locking up the DataContext and throwing the error. Could this be a case for wrapping each of the DataContext LINQ calls in a lock(){} to obtain exclusivity to that type and ensure other requests are queued?

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  • Custom Detail in Linq-to-SQL Master-Detail DataGridViews

    - by Andres
    Hi, looking for a way to create Linq-to-SQL Master-Detail WinForms DataGridViews where the Detail part of the Linq query is a custom one. Can do fine this: DataClasses1DataContext db = new DataClasses1DataContext(".\\SQLExpress"); var myQuery = from o in db.Orders select o; dataGridView1.DataSource = new BindingSource() { DataSource = myQuery }; dataGridView2.DataSource = new BindingSource() { DataSource = dataGridView1.DataSource, DataMember = "OrderDetails" }; but I'd like to have the Detail part under my precise control, like var myQuery = from o in db.Orders join od in db.OrderDetails on o.ID equals od.OrderID into MyOwnSubQuery select o; and use it for the second grid: dataGridView2.DataSource = new BindingSource() { DataSource = dataGridView1.DataSource, DataMember = "MyOwnSubQuery" // not working... }; the real reason I want it is a bit more complex (I'd like to have the Detail part to be some not-pre-defined join actually), but I'm hoping the above conveyed the idea. Can I only have the Detail part as a plain sub-table coming out of the pre-defined relation or can I do more complex stuff with the Detail part? Does anyone else feel this is kind of limited (if the first example is the best we can do)? Thanks!

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  • make reference to an empty query in flex

    - by Adam
    a bit of a dumb questions I'm sure I'm trying to allow user to set an item to be default. I've got a function that run a query to first find the current default item. Then runs a second query that unsets the current default item. Then a third query runs to set the new user selected item to be the default. This seem to work fine when a default item has been perviously selected, but when I try to set the default item initially I get the good old "Cannot access a property or method of a null object reference." error. This is because the first query that runs returns no items I'm sure. So I need to write an if statement that if the first query returns nothing to skip the second and go right to the third. The only problem is I can't make a reference to a null object. So how do I go about writing this statement. Thanks

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  • Using LINQ on observable with GroupBy and Sum aggregate

    - by Mark Oates
    I have the following block of code which works fine; var boughtItemsToday = (from DBControl.MoneySpent bought in BoughtItemDB.BoughtItems select bought); BoughtItems = new ObservableCollection<DBControl.MoneySpent>(boughtItemsToday); It returns data from my MoneySpent table which includes ItemCategory, ItemAmount, ItemDateTime. I want to change it to group by ItemCategory and ItemAmount so I can see where I am spending most of my money, so I created a GroupBy query, and ended up with this; var finalQuery = boughtItemsToday.AsQueryable().GroupBy(category => category.ItemCategory); BoughtItems = new ObservableCollection<DBControl.MoneySpent>(finalQuery); Which gives me 2 errors; Error 1 The best overloaded method match for 'System.Collections.ObjectModel.ObservableCollection.ObservableCollection(System.Collections.Generic.List)' has some invalid arguments Error 2 Argument 1: cannot convert from 'System.Linq.IQueryable' to 'System.Collections.Generic.List' And this is where I'm stuck! How can I use the GroupBy and Sum aggregate function to get a list of my categories and the associated spend in 1 LINQ query?! Any help/suggestions gratefully received. Mark

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  • Update query with conditional?

    - by dmontain
    I'm not sure if this possible. If not, let me know. I have a PDO mysql that updates 3 fields. $update = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2, field3=:field3 WHERE key=:key"); But I want field3 to be updated only when $update3 = true; (meaning that the update of field3 is controlled by a conditional statement) Is this possible to accomplish with a single query? I could do it with 2 queries where I update field1 and field2 then check the boolean and update field3 if needed in a separate query. //run this query to update only fields 1 and 2 $update_part1 = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2 WHERE key=:key"); //if field3 should be update, run a separate query to update it separately if ($update3){ $update_part2 = $mypdo->prepare("UPDATE tablename SET field3=:field3 WHERE key=:key"); } But hopefully there is a way to accomplish this in 1 query?

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