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• Select a Dictionary<T1, T2> with LINQ

  - by Rich

  I have used the "select" keyword and extension method to return an IEnumerable<T> with LINQ, but I have a need to return a generic Dictionary<T1, T2> and can't figure it out. The example I learned this from used something in a form similar to the following: IEnumerable<T> coll = from x in y select new SomeClass{ prop1 = value1, prop2 = value2 }; I've also done the same thing with extension methods. I assumed that since the items in a Dictionary<T1, T2> can be iterated as KeyValuePair<T1, T2> that I could just replace "SomeClass" in the above example with "new KeyValuePair<T1, T2> { ...", but that didn't work (Key and Value were marked as readonly, so I could not compile this code). Is this possible, or do I need to do this in multiple steps? Thanks.

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• Linq - Grouping where items fall in multiple groups?

  - by PirateKitten

  Is it possible using Linq to create a group where items fall into more than one group? Using the following trivial example: public class Data { public string ID; public int From; public int To; } And this list: List<Data> data = new List<Data>() { new Data() { ID = "A", From = 1, To = 3 }, // Call this A new Data() { ID = "B", From = 1, To = 2 }, // Call this B new Data() { ID = "C", From = 2, To = 3 } // Call this C }; I'd like to group by each possible integer in the ranges From and To (though instead of finding the min + max I could supply the query with the range I want, for example 1 to 3), and in each group would be a reference to the Data instance where the grouping int fits in its range. Hard to explain, easier to show each group and the instances I'd expect in each: [Group 1] 1 - A, B [Group 2] 2 - A, B, C [Group 3] 3 - A, C Is this possible? Or must groups be mutually exclusive?

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• where clause in linq query

  - by masoud

  in the below code "transmittalno.TransID" always has value but "doctranstocon.Transid" sometimes has value and sometimes does not, so when "doctranstocon.Transid" has value I have no problem but when there is not any value, when compare in the where clause like :"transmittalno.TransID == doctranstocon.Transid". It returns error" Object reference not set to an instance of an object." TranstoCons = from doctranstocon in _DocTranstoCons where ( transmittalno.TransID == doctranstocon.Transid ) select doctranstocon.tblTranstoCon I like TranstoCons returns null when there is not any value for " doctranstocon.Transid " How I can handle this error in the below linq query: var query = from transmittalno in _Transmittals Select new TransmittaltoConPresentationModel { TransID = transmittalno.TransID, Transmittal = transmittalno.TRANSMITTAL, TranstoCons = from doctranstocon in _DocTranstoCons where ( transmittalno.TransID == doctranstocon.Transid ) select doctranstocon.tblTranstoCon };

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• Linq 2 Sql DateTime format to string yyyy-MM-dd

  - by Bogdan Maxim

  Basically, i need the equivalent of T-SQL CONVERT(NVARCHAR(10), datevalue, 126) I've tried: from t in ctx.table select t.Date.ToString("yyyy-MM-dd") but it throws not supported exception from t in ctx.table select "" + t.Date.Year + "-" + t.Date.Month + "-" + t.Date.Day but i don't think it's an usable solution, because i might need to be able to change the format. The only option I see is to use Convert.ToString(t.Date, FormatProvider), but i need a format provider, and I'm not sure it works either.

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• Hangs with LINQ-SQL Server and TransactionScope

  - by Zian Choy

  I'm encountering a hang when the program tries to access the fruit database. I've already enabled network access MSDTC on both my development computer and the SQL Server server. Code: (pardon the code coloring...SO's misinterpreting my VB .NET) Using ts As New TransactionScope Dim fruit As New FruitDataContext Dim thingies As New ThingiesDataContext If (From f In fruit.tblApples Where f.Rotten = True).Count >= 1 Then 'Record today's date as the day that the rotten apples were dumped. End If 'Other complicated code that uses ThingiesDataContext and FruitDataContext du.SubmitChanges() ts.Complete() End Using

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• Using ASP.NET MVC, Linq To SQL, and StructureMap causing DataContext to cache data

  - by Dragn1821

  I'll start by telling my project setup: ASP.NET MVC 1.0 StructureMap 2.6.1 VB I've created a bootstrapper class shown here: Imports StructureMap Imports DCS.Data Imports DCS.Services Public Class BootStrapper Public Shared Sub ConfigureStructureMap() ObjectFactory.Initialize(AddressOf StructureMapRegistry) End Sub Private Shared Sub StructureMapRegistry(ByVal x As IInitializationExpression) x.AddRegistry(New MainRegistry()) x.AddRegistry(New DataRegistry()) x.AddRegistry(New ServiceRegistry()) x.Scan(AddressOf StructureMapScanner) End Sub Private Shared Sub StructureMapScanner(ByVal scanner As StructureMap.Graph.IAssemblyScanner) scanner.Assembly("DCS") scanner.Assembly("DCS.Data") scanner.Assembly("DCS.Services") scanner.WithDefaultConventions() End Sub End Class I've created a controller factory shown here: Imports System.Web.Mvc Imports StructureMap Public Class StructureMapControllerFactory Inherits DefaultControllerFactory Protected Overrides Function GetControllerInstance(ByVal controllerType As System.Type) As System.Web.Mvc.IController Return ObjectFactory.GetInstance(controllerType) End Function End Class I've modified the Global.asax.vb as shown here: ... Sub Application_Start() RegisterRoutes(RouteTable.Routes) 'StructureMap BootStrapper.ConfigureStructureMap() ControllerBuilder.Current.SetControllerFactory(New StructureMapControllerFactory()) End Sub ... I've added a Structure Map registry file to each of my three projects: DCS, DCS.Data, and DCS.Services. Here is the DCS.Data registry: Imports StructureMap.Configuration.DSL Public Class DataRegistry Inherits Registry Public Sub New() 'Data Connections. [For](Of DCSDataContext)() _ .HybridHttpOrThreadLocalScoped _ .Use(New DCSDataContext()) 'Repositories. [For](Of IShiftRepository)() _ .Use(Of ShiftRepository)() [For](Of IMachineRepository)() _ .Use(Of MachineRepository)() [For](Of IShiftSummaryRepository)() _ .Use(Of ShiftSummaryRepository)() [For](Of IOperatorRepository)() _ .Use(Of OperatorRepository)() [For](Of IShiftSummaryJobRepository)() _ .Use(Of ShiftSummaryJobRepository)() End Sub End Class Everything works great as far as loading the dependecies, but I'm having problems with the DCSDataContext class that was genereated by Linq2SQL Classes. I have a form that posts to a details page (/Summary/Details), which loads in some data from SQL. I then have a button that opens a dialog box in JQuery, which populates the dialog from a request to (/Operator/Modify). On the dialog box, the form has a combo box and an OK button that lets the user change the operator's name. Upon clicking OK, the form is posted to (/Operator/Modify) and sent through the service and repository layers of my program and updates the record in the database. Then, the RedirectToAction is called to send the user back to the details page (/Summary/Details) where there is a call to pull the data from SQL again, updating the details view. Everything works great, except the details view does not show the new operator that was selected. I can step through the code and see the DCSDataContext class being accessed to update the operator (which does actually change the database record), but when the DCSDataContext is accessed to reload the details objects, it pulls in the old value. I'm guessing that StructureMap is causing not only the DCSDataContext class but also the data to be cached? I have also tried adding the following to the Global.asax, but it just ends up crashing the program telling me the DCSDataContext has been disposed... Private Sub MvcApplication_EndRequest(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.EndRequest StructureMap.ObjectFactory.ReleaseAndDisposeAllHttpScopedObjects() End Sub Can someone please help?

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• SQL Server stored procedures - update column based on variable name..?

  - by ClarkeyBoy

  Hi, I have a data driven site with many stored procedures. What I want to eventually be able to do is to say something like: For Each @variable in sproc inputs UPDATE @TableName SET @variable.toString = @variable Next I would like it to be able to accept any number of arguments. It will basically loop through all of the inputs and update the column with the name of the variable with the value of the variable - for example column "Name" would be updated with the value of @Name. I would like to basically have one stored procedure for updating and one for creating. However to do this I will need to be able to convert the actual name of a variable, not the value, to a string. Question 1: Is it possible to do this in T-SQL, and if so how? Question 2: Are there any major drawbacks to using something like this (like performance or CPU usage)? I know if a value is not valid then it will only prevent the update involving that variable and any subsequent ones, but all the data is validated in the vb.net code anyway so will always be valid on submitting to the database, and I will ensure that only variables where the column exists are able to be submitted. Many thanks in advance, Regards, Richard Clarke Edit: I know about using SQL strings and the risk of SQL injection attacks - I studied this a bit in my dissertation a few weeks ago. Basically the website uses an object oriented architecture. There are many classes - for example Product - which have many "Attributes" (I created my own class called Attribute, which has properties such as DataField, Name and Value where DataField is used to get or update data, Name is displayed on the administration frontend when creating or updating a Product and the Value, which may be displayed on the customer frontend, is set by the administrator. DataField is the field I will be using in the "UPDATE Blah SET @Field = @Value". I know this is probably confusing but its really complicated to explain - I have a really good understanding of the entire system in my head but I cant put it into words easily. Basically the structure is set up such that no user will be able to change the value of DataField or Name, but they can change Value. I think if I were to use dynamic parameterised SQL strings there will therefore be no risk of SQL injection attacks. I mean basically loop through all the attributes so that it ends up like: UPDATE Products SET [Name] = '@Name', Description = '@Description', Display = @Display Then loop through all the attributes again and add the parameter values - this will have the same effect as using stored procedures, right?? I dont mind adding to the page load time since this is mainly going to affect the administration frontend, and will marginly affect the customer frontend.

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• querying nested array elements in C#

  - by the berserker

  I have following object structure, deseralized from XML (WS): <ns2:Category> <ns2:CategoryId>800003</ns2:CategoryId> <ns2:CategoryName>Name1</ns2:CategoryName> <ns2:Categories> <ns2:Category> <ns2:CategoryId>800008</ns2:CategoryId> <ns2:CategoryName>Name2</ns2:CategoryName> <ns2:Categories> <ns2:Category> <ns2:CategoryId>800018</ns2:CategoryId> <ns2:CategoryName>Name3</ns2:CategoryName> <ns2:Categories/> </ns2:Category> <ns2:Category> <ns2:CategoryId>800028</ns2:CategoryId> <ns2:CategoryName>Name4</ns2:CategoryName> <ns2:Categories/> </ns2:Category> </ns2:Categories> </ns2:Category> <ns2:Category> <ns2:CategoryId>800009</ns2:CategoryId> <ns2:CategoryName>Name5</ns2:CategoryName> <ns2:Categories> <ns2:Category> <ns2:CategoryId>800019</ns2:CategoryId> <ns2:CategoryName>Name6</ns2:CategoryName> <ns2:Categories> <ns2:Category> <ns2:CategoryId>800119</ns2:CategoryId> <ns2:CategoryName>Name7</ns2:CategoryName> <ns2:Categories/> </ns2:Category> <ns2:Category> <ns2:CategoryId>800219</ns2:CategoryId> <ns2:CategoryName>Name111</ns2:CategoryName> <ns2:Categories/> </ns2:Category> </ns2:Categories> </ns2:Category> </ns2:Categories> </ns2:Category> </ns2:Categories> </ns2:Category> How would I find Category object with CategoryId 800119 efficiently? So, Im looking for something like FindCategory(long categoryId) - Prefferably with LINQ to objects. Any other option?

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• Constructor or Explicit cast

  - by Felan

  In working with Linq to Sql I create a seperate class to ferry data to a web page. To simplify creating these ferry objects I either use a specialized constructor or an explicit conversion operator. I have two questions. First which approach is better from a readibility perspective? Second while the clr code that is generated appeared to be the same to me, are there situations where one would be treated different than the other by the compiler (in lambda's or such). Example code (DatabaseFoo uses specialized constructor and BusinessFoo uses explicit operator): public class DatabaseFoo { private static int idCounter; // just to help with generating data public int Id { get; set; } public string Name { get; set; } public DatabaseFoo() { Id = idCounter++; Name = string.Format("Test{0}", Id); } public DatabaseFoo(BusinessFoo foo) { this.Id = foo.Id; this.Name = foo.Name; } } public class BusinessFoo { public int Id { get; set; } public string Name { get; set; } public static explicit operator BusinessFoo(DatabaseFoo foo) { return FromDatabaseFoo(foo); } public static BusinessFoo FromDatabaseFoo(DatabaseFoo foo) { return new BusinessFoo {Id = foo.Id, Name = foo.Name}; } } public class Program { static void Main(string[] args) { Console.WriteLine("Creating the initial list of DatabaseFoo"); IEnumerable<DatabaseFoo> dafoos = new List<DatabaseFoo>() { new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo()}; foreach(DatabaseFoo dafoo in dafoos) Console.WriteLine(string.Format("{0}\t{1}", dafoo.Id, dafoo.Name)); Console.WriteLine("Casting the list of DatabaseFoo to a list of BusinessFoo"); IEnumerable<BusinessFoo> bufoos = from x in dafoos select (BusinessFoo) x; foreach (BusinessFoo bufoo in bufoos) Console.WriteLine(string.Format("{0}\t{1}", bufoo.Id, bufoo.Name)); Console.WriteLine("Creating a new list of DatabaseFoo by calling the constructor taking BusinessFoo"); IEnumerable<DatabaseFoo> fufoos = from x in bufoos select new DatabaseFoo(x); foreach(DatabaseFoo fufoo in fufoos) Console.WriteLine(string.Format("{0}\t{1}", fufoo.Id, fufoo.Name)); } }

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• Linq - get compare with transliterated value of fields

  - by Maxim

  Hi! I have a table (sql server). One of its columns ('Name') Contains Cyrillic values. From parameters i recieve value, that contains in this field but the are transliterated. i mean something like: var q = from r in m_DataContext.Table where CTransliteration.Transliterate(r.Name).Contains(trans_text) select r; How can i transliterate value on-fly?

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• ASP.NET LINQ to SQL SubmitChanges() doesn't update the database

  - by Alex

  In my 2nd ASP.NET MVC project I'm facing a very weird problem: when I call the SubmitChanges method of the DataContext class, nothing updates in the database. It's weird because everything works fine with my first project. I'm using a remote database created in Sql Server Management Studio, I tried doing some queries there and in Visual Studio 2010 (where I have the connection to the database), they all work. Where might the problem be hidden?

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• Using XAML + designer to edit Plain Old CLR Objects?

  - by Joe White

  I want to write a POCO in XAML, and use a DataTemplate to display that object in the GUI at runtime. So far, so good; I know how to do all that. Since I'll already have a DataTemplate that can transform my POCO into a WPF visual tree, is there any way to get the Visual Studio designer to play along, and have the Design View show me the POCO+DataTemplate's resulting GUI, as I edit the POCO's XAML? (Obviously the designer wouldn't know how to edit the "design view"; I wouldn't expect the Toolbox or click-and-drag to work on the design surface. That's fine -- I just want to see a preview as I edit.) If you're curious, the POCOs in question would be level maps for a game. (At this point, I'm not planning to ship an end-user map editor, so I'll be doing all the editing myself in Visual Studio.) So the XAML isn't WPF GUI objects like Window and UserControl, but it's still not something where I would want to blindly bang out some XAML and hope for the best. I want to see what I'm doing (the GUI map) as I'm doing it. If I try to make a XAML file whose root is my map object, the designer shows "Intentionally Left Blank - The document root element is not supported by the visual designer." It does this even if I've defined a DataTemplate in App.xaml's <Application.Resources>. But I know the designer can show my POCO, when it's inside a WPF object. One possible way of accomplishing what I want would be to have a ScratchUserControl that just contains a ContentPresenter, and write my POCO XAML inside that ContentPresenter's Content property, e.g.: <UserControl ...> <ContentPresenter> <ContentPresenter.Content> <Maps:Map .../> </ContentPresenter.Content> </ContentPresenter> </UserControl> But then I would have to be sure to copy the content back out into its own file when I was done editing, which seems tedious and error-prone, and I don't like tedious and error-prone. And since I can preview my XAML this way, isn't there some way to do it without the UserControl?

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• How to use the IN operator in linq

  - by Hallaghan

  I'm querying a view and filtering the results with a column named status. I'd like to query it so I can search for rows with different status, by using the IN operator as I'd do in SQL. As so: SELECT * FROM VIEW WHERE Status in ('....', '.....') How can I achieve this?

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• Manual Linq to SQL entity framework mapping

  - by kprobst

  I've been playing with the O/R designer in VS and I was wondering if someone could shed come light on this. I'm used to OR mappers that are largely manual (homegrown and e.g., NHibernate). I don't mind encoding the entity classes myself, since they don't change all that often to begin with, and I have this irrational fear of designers and auto generated code as it is. I have noticed that the generated entity classes contain a lot of boilerplate extensibility methods, e.g. On[Property]Changed() and so on where [Property] is a mapped member of the class. These are placed in the setters of the property accessors. I assume it's OK if I don't include these when I do my hand coding, correct? They would be nice if I needed some sort of interception pattern but that's certainly not the case. I guess I just need to know if any of those methods are required by the entity framework to keep track of changes to the mapping types in order for things to work when updating the database. Thanks!

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• Visual C# 2008 Express connection to SQL Server 2008 Express problem

  - by Phil

  Hi guys, I have a problem with Visual C# 2008 express (SP1) connecting to SQL Server 2008 express. The "Add Connection" window (wherever initiated) doesn't list existing sql server and no option for sql server except a compact edition. Note that, I've got the VWD 2008 express (SP1) on the same machine which shows the window regularly (with SQL server listed) and SQL Server Management studio works fine with the server as well. I've seen other similar posts, did take some advices: reinstalled the VC#, services run ok, etc... but with no success with VC# so far. Again, on the same machine the VWD shows the dialog with sql server option regularly, but VC# shows only 3 options in "Change data source" dialog (1. Microsoft Access Database File (OLE DB) 2. Microsoft SQL Server Compact 3.5, 3. Microsoft SQL Server Database File) Any idea? Thanks in advice, Phil

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• Calling SubmitChanges on DataContext does not update database.

  - by drasto

  In C# ASP.NET MVC application I use Link to SQL to provide data for my application. I have got simple database schema like this: In my controller class I reference this data context called Model (as you can see on the right side of picture in properties) like this: private Model model = new Model(); I've got a table (List) of Series rendered on my page. It renders properly and I was able to add delete functionality to delete Series like this: public ActionResult Delete(int id) { model.Series.DeleteOnSubmit(model.Series.SingleOrDefault(s => s.ID == id)); model.SubmitChanges(); return RedirectToAction("Index"); } Where appropriate action link looks like this: <%: Html.ActionLink("Delete", "Delete", new { id=item.ID })%> Also create (implemented in similar way) works fine. However edit does not work. My edit looks like this: public ActionResult Edit(int id) { return View(model.Series.SingleOrDefault(s => s.ID == id)); } [HttpPost] public ActionResult Edit(Series series) { if (ModelState.IsValid) { UpdateModel(series); series.Title = series.Title + " some string to ensure title has changed"; model.SubmitChanges(); return RedirectToAction("Index"); } I have controlled that my database has a primary key set up correctly. I debugged my application and found out that everything works as expected until the line with model.SubmitChanges();. This command does not apply the changes of Title property(or any other) against the database. Please help.

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• Sql Server Backup and move backup file: How to cope with file permissions?

  - by Stefan Steinegger

  With our product we have a simple backup tool for the sql server database. This tool should just make a full backup and restore to and from any folder. Of course, the user (usually an administrator) needs permission to write to the target folder. To avoid the problem of not being able to perform a backup to a network drive, I write the backup to a temp file in the Sql Server backup directory. Then I move it to the target folder. This requires permission to delete the temporary file from the sql servers backup folder. Restore is the same in the other direction. This seemed to work fine until someone tested it on vista, where the user does not have write access to the backup folder by default. So there are many solutions to solve this, but none of them seemed to be really nice. One solution would be to find another folder for the temporary file. Both the sql server user as well as the administrator performing the backup need read and write permissions. Is there such a directory? Any other ideas? Thanks a lot.

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• "Attach or Add an entity that is not new...loaded from another DataContext. This is not supported."

  - by sah302

  Similar error as other questions, but not quite the same, I am not trying to attach anything. What I am trying to do is insert a new row into a linking table, specifically UserAccomplishment. Relations are set in LINQ to User and Accomplishment Tables. I have a generic insert function: Public Function insertRow(ByVal entity As ImplementationType) As Boolean If entity IsNot Nothing Then Dim lcfdatacontext As New LCFDataContext() Try lcfdatacontext.GetTable(Of ImplementationType)().InsertOnSubmit(entity) lcfdatacontext.SubmitChanges() lcfdatacontext.Dispose() Return True Catch ex As Exception Return False End Try Else Return False End If End Function If you try and give UserAccomplishment the two appropriate objects this will naturally crap out if either the User or Accomplishment already exist. It only works when both user and accomplishment don't exist. I expected this behavior. What does work is simply giving the userAccomplishment object a user.id and accomplishment.id and populating the rest of the fields. This works but is kind of awkward to use in my app, it would be much easier to simply pass in both objects and have it work out what already exists and what doesn't. Okay so I made the following (please ignore the fact that this is horribly inefficient because I know it is): Public Class UserAccomplishmentDao Inherits EntityDao(Of UserAccomplishment) Public Function insertLinkerObjectRow(ByVal userAccomplishment As UserAccomplishment) Dim insertSuccess As Boolean = False If Not userAccomplishment Is Nothing Then Dim userDao As New UserDao() Dim accomplishmentDao As New AccomplishmentDao() Dim user As New User() Dim accomplishment As New Accomplishment() 'see if either object already exists in db' user = userDao.getOneByValueOfProperty("Id", userAccomplishment.User.Id) accomplishment = accomplishmentDao.getOneByValueOfProperty("Id", userAccomplishment.Accomplishment.Id) If user Is Nothing And accomplishment Is Nothing Then 'neither the user or the accomplishment exist, both are new so insert them both, typical insert' insertSuccess = Me.insertRow(userAccomplishment) ElseIf user Is Nothing And Not accomplishment Is Nothing Then 'user is new, accomplishment is not new, so just insert the user, and the relation in userAccomplishment' Dim userWithExistingAccomplishment As New UserAccomplishment(userAccomplishment.User, userAccomplishment.Accomplishment.Id, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(userWithExistingAccomplishment) ElseIf Not user Is Nothing And accomplishment Is Nothing Then 'user is not new, accomplishment is new, so just insert the accomplishment, and the relation in userAccomplishment' Dim existingUserWithAccomplishment As New UserAccomplishment(userAccomplishment.UserId, userAccomplishment.Accomplishment, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(existingUserWithAccomplishment) Else 'both are not new, just add the relation' Dim userAccomplishmentBothExist As New UserAccomplishment(userAccomplishment.User.Id, userAccomplishment.Accomplishment.Id, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(userAccomplishmentBothExist) End If End If Return insertSuccess End Function End Class Alright, here I basically check if the supplied user and accomplishment already exists in the db, and if so call an appropriate constructor that will leave whatever already exists empty, but supply the rest of the information so the insert can succeed. However, upon trying an insert: Dim result As Boolean = Me.userAccomplishmentDao.insertLinkerObjectRow(userAccomplishment) In which the user already exists, but the accomplishment does not (the 99% typical scenario) I get the error: "An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported." I have debugged this multiple times now and am not sure why this is occuring, if either User or Accomplishment exist, I am not including it in the final object to try to insert. So nothing appears to be attempted to be added. Even in debug, upon insert, the object was set to empty. So the accomplishment is new and the user is empty. 1) Why is it still saying that and how can I fix it ..using my current structure 2) Pre-emptive 'use repository pattern answers' - I know this way kind of sucks in general and I should be using the repository pattern. However, I can't use that in the current project because I don't have time to refactor that due to my non existence knowledge of it and time constraints. The usage of the app is going to so small that the inefficient use of datacontext's and what have you won't matter so much. I can refactor it once it's up and running, but for now I just need to 'push through' with my current structure. Edit: I also just tested this when having both already exists, and only insert each object's IDs into the table, that works. So I guess I could manually insert whichever object doesn't exist as a single insert, then put the ids only into the linking table, but I still don't know why when one object exists, and I make it empty, it doens't work.

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• Wildcards in T-SQL LIKE vs. ASP.net parameters

  - by Vinzcent

  In my SQL statement I use wildcards. But when I try to select something, it never select something. While when I execute the query in Microsoft SQL Server Management Studio, it works fine. What am I doing wrong? Click handler protected void btnTitelAuteur_Click(object sender, EventArgs e) { cvalTitelAuteur.Enabled = true; cvalTitelAuteur.Validate(); if (Page.IsValid) { objdsSelectedBooks.SelectMethod = "getBooksByTitleAuthor"; objdsSelectedBooks.SelectParameters.Clear(); objdsSelectedBooks.SelectParameters.Add(new Parameter("title", DbType.String)); objdsSelectedBooks.SelectParameters.Add(new Parameter("author", DbType.String)); objdsSelectedBooks.Select(); gvSelectedBooks.DataBind(); pnlZoeken.Visible = false; pnlKiezen.Visible = true; } } In my Data Access Layer public static DataTable getBooksByTitleAuthor(string title, string author) { string sql = "SELECT 'AUTHOR' = tblAuthors.FIRSTNAME + ' ' + tblAuthors.LASTNAME, tblBooks.*, tblGenres.GENRE " + "FROM tblAuthors INNER JOIN tblBooks ON tblAuthors.AUTHOR_ID = tblBooks.AUTHOR_ID INNER JOIN tblGenres ON tblBooks.GENRE_ID = tblGenres.GENRE_ID " +"WHERE (tblBooks.TITLE LIKE '%@title%');"; SqlDataAdapter da = new SqlDataAdapter(sql, GetConnectionString()); da.SelectCommand.Parameters.Add("@title", SqlDbType.Text); da.SelectCommand.Parameters["@title"].Value = title; DataSet ds = new DataSet(); da.Fill(ds, "Books"); return ds.Tables["Books"]; }

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• LinqToSQL: Not possible to update PrimaryKey?

  - by Zuhaib

  I have a simple table (lets call it Table1) that has a NVARCHAR field as the PK. Table1 has no association with any other tables. When I update Table1's PK column using LinqToSQL it fails. If I update other column it succeeds. I could delete this row and insert new one in Table1, but I don't want to. There is a transaction table which has Table1's PK column as a column. When the PK of Table1 is changed I want no effect in the transaction table. But when the row from Table1 is deleted, I want the transaction rows to be deleted. The cascading is done via Trigger. As there is not association between these two tables, if I update the PK column of Table1 using normal SQL, it works and there is no effect on the transaction table as expected. When I delete the row the trigger deletes the rows from transaction table. For this reason I can't delete and then add new row in Table1. So what can be done to successfully update the PrimaryKey of the Table1?

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• Hidden features of PL/SQL

  - by Adam Paynter

  In light of the "Hidden features of..." series of questions, what little-known features of PL/SQL have become useful to you? Edit: Features specific to PL/SQL are preferred over features of Oracle's SQL syntax. However, because PL/SQL can use most of Oracle's SQL constructs, they may be included if they make programming in PL/SQL easier.

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• How does C#'s DateTime.Now affect query plan caching in SQL Server?

  - by Bill Paetzke

  Given: Let's say we have a stored procedure. It reports data back to a user on a webpage. The user can set a date range. If the user sets today's date as the "end date," which includes today's data, the web app passes DateTime.Now to the sql proc. Let's say that one user runs a report--5/1/2010 to now--over and over several times. On the webpage, the user sees "5/1/2010" to "5/4/2010." But the web app passes DateTime.Now to the sql proc as the end date. So, the end date in the proc will always be different, although the user is querying a similar date range. Assume the number of records in the table and number of users are large. So any performance gains matter. Hence the importance of the question. Question: Does passing DateTime.Now as a parameter to a proc prevent SQL Server from caching the query plan? If so, then is the web app missing out on huge performance gains? Possible Solution: I thought DateTime.Today.AddDays(1) would be a possible solution. It would allow the user to get the latest data and always pass the same end date to the sql proc--"5/5/2010" in this case. Please speak to this as well. Sample proc and execution (if that helps to understand): CREATE PROCEDURE GetFooData @StartDate datetime @EndDate datetime AS SELECT * FROM Foo WHERE LogDate >= @StartDate AND LogDate < @EndDate Here's a sample execution using DateTime.Now: EXEC GetFooData '2010-05-01', '2010-05-04 15:41:27' -- passed in DateTime.Now Here's a sample execution using DateTime.Today.AddDays(1) EXEC GetFooData '2010-05-01', '2010-05-05' -- passed in DateTime.Today.AddDays(1) The same data is returned for both procs, since the current time is: 2010-05-04 15:41:27.

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• How SSD hard drive affected speed of your website (asp.net/linq/ms sql database)

  - by Sergey Osypchuk

  I have a small database (<1G) But we have a lot of complex logi? in website and client complains on render time, which is 3-5 seconds. We are not google, and thousands of users a day is our dream, so size is not a problem, but speed is important. Can anybody share with experience with SSD drives for ASP.NET (MVC)/LINQ/MS SQL based application ? How you performance increased? UPDATE: this whitepaper states that it will be 20 times faster. http://www.texmemsys.com/files/f000174.pdf

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• Advice needed: cold backup for SQL Server 2008 Express?

  - by Mikey Cee

  What are my options for achieving a cold backup server for SQL Server Express instance running a single database? I have an SQL Server 2008 Express instance in production that currently represents a single point of failure for my application. I have a second physical box sitting at the installation that is currently doing nothing. I want to somehow replicate my database in near real time (a little bit of data loss is acceptable) to the second box. The database is very small and resources are utilized very lightly. In the case that the production server dies, I would manually reconfigure my application to point to the backup server instead. Although Express doesn't support log shipping, I am thinking that I could manually script a poor man's version of it, where I use batch files to take the logs and copy them across the network and apply them to the second server at 5 minute intervals. Does anyone have any advice on whether this is technically achievable, or if there is a better way to do what I am trying to do? Note that I want to avoid having to pay for the full version of SQL Server and configure mirroring as I think it is an overkill for this application. I understand that other DB platforms may present suitable options (eg. a MySQL Cluster), but for the purposes of this discussion, let's assume we have to stick to SQL Server.

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• How does DateTime.Now affect query plan caching in SQL Server?

  - by Bill Paetzke

  Question: Does passing DateTime.Now as a parameter to a proc prevent SQL Server from caching the query plan? If so, then is the web app missing out on huge performance gains? Possible Solution: I thought DateTime.Today.AddDays(1) would be a possible solution. It would pass the same end-date to the sql proc (per day). And the user would still get the latest data. Please speak to this as well. Given Example: Let's say we have a stored procedure. It reports data back to a user on a webpage. The user can set a date range. If the user sets today's date as the "end date," which includes today's data, the web app passes DateTime.Now to the sql proc. Let's say that one user runs a report--5/1/2010 to now--over and over several times. On the webpage, the user sees 5/1/2010 to 5/4/2010. But the web app passes DateTime.Now to the sql proc as the end date. So, the end date in the proc will always be different, although the user is querying a similar date range. Assume the number of records in the table and number of users are large. So any performance gains matter. Hence the importance of the question. Example proc and execution (if that helps to understand): CREATE PROCEDURE GetFooData @StartDate datetime @EndDate datetime AS SELECT * FROM Foo WHERE LogDate >= @StartDate AND LogDate < @EndDate Here's a sample execution using DateTime.Now: EXEC GetFooData '2010-05-01', '2010-05-04 15:41:27' -- passed in DateTime.Now Here's a sample execution using DateTime.Today.AddDays(1) EXEC GetFooData '2010-05-01', '2010-05-05' -- passed in DateTime.Today.AddDays(1) The same data is returned for both procs, since the current time is: 2010-05-04 15:41:27.

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