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  • How to check if a child-object is populated

    - by TheQ
    How can i check if a child-object of a linq-object is populated or not? Example code below. My model have two methods, one joins data, and the other does not: public static Member GetMemberWithPhoto(Guid memberId) { using (DataContext db = new DataContext()) { DataLoadOptions dataLoadOptions = new DataLoadOptions(); dataLoadOptions.LoadWith<Member>(x => x.UserPhoto); db.LoadOptions = dataLoadOptions; var query = from x in db.Members where x.MemberId == memberId select x; return query.FirstOrDefault(); } } public static Member GetMember(Guid memberId) { using (DataContext db = new DataContext()) { var query = from x in db.Members where x.MemberId == memberId select x; return query.FirstOrDefault(); } } Then my control have the following code: Member member1 = Member.GetMemberWithPhoto(memberId); Member member2 = Member.GetMember(memberId); Debug.WriteLine(member1.UserPhoto.ToString()); Debug.WriteLine(member2.UserPhoto.ToString()); The last line will generate a "Cannot access a disposed object" exception. I know that i can get rid of that exception just by not disposing the datacontext, but then the last line will generate a new query to the database, and i don't want that. What i would like is something like: Debug.WriteLine((member1.UserPhoto.IsPopulated()) ? member1.UserPhoto.ToString() : "none"); Debug.WriteLine((member2.UserPhoto.IsPopulated()) ? member2.UserPhoto.ToString() : "none"); Is it possible?

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  • Array Indexing Properties of A Class

    - by Chris
    I have a class that has several properties: class Person { string Name; int Age; DateTime BirthDate; } Then I have a sort of wrapper class with a List<Person>. Within this wrapper class I want to be able to do something like Wrapper["Name"] that returns a new List<string> using .Select(x=>x.Name). How do I create a wrapper class around an IEnumerable that supports mapping a string to the Property name? Something like the pseudo code below, but obviously it doesn't work. I'm 99.9% sure the solution will have to use Reflection and thats fine. class Wrapper { List<Person> PersonList; List<dynamic> this[string Column] { return PersonList.Select(x => x.[Column]).ToList(); } } This may not seem like a good design, but its a fix to eventually enable the correct design from .NET 2.0 days. As I have it right now, the data is stored in Columns, so there is actually a List of Lists within my class right now. Using the above example there would be three ILists (with a string Title) Name, Age, and Birthdate. Everything is currently predicated on addressing the columns by their "string" name. I'm trying to convert the data structure to row based with an IEnumberable interface to allow Linq eventually while still maintaining the functionality of my current code. Is converting the code to a Row based IEnumberable a good idea?

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  • Centering Divisions Around Zero

    - by Mark
    I'm trying to create something that sort of resembles a histogram. I'm trying to create buckets from an array. Suppose I have a random array doubles between -10 and 10; this is very simplified. I then want to specify a center point, in this case 0 and the number of buckets. If I want 4 buckets the division would be -10 to -5, -5 to 0, 0 to 5 and 5 to 10. Not that complicated right. Now if I change the min and max to -12 and -9 and as for 4 divisions its more complicated. I either want a division at -3 and 3; it is centered around 0 ; or one at -6 to 0 and 0 to 6. Its not that hard to find the division size = Math.Ceiling((Abs(Max) + Abs(Min)) / Divisions) Then you would basically have an if statement to determine whether you want it centered on 0 or on an edge. You then iterate out from either 0 or DivisionSize/2 depending on the situation. You may not ALWAYS end up with the specified number of divisions but it will be close. Then you iterate through the array and increment the bin count. Does this seem like a good way to go about this? This method would surely work but it does not seem to be the most elegant. I'm curious as to whether the creation of the bins and the counting from the list could be done in a clever class with linq in a more elegant way? Something like creating the bins and then having each bin be a property {get;} that returns list.Count(x=> x >= Lower && x < Upper).

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  • Is it possible to create the following XML using Xdocument(C#3.0)

    - by Newbie
    <?xml version='1.0' encoding='UTF-8'?> <StockMarket> <StockDate Day = "02" Month="06" Year="2010"> <Stock> <Symbol>ABC</Symbol> <Amount>110.45</Amount> </Stock> <Stock> <Symbol>XYZ</Symbol> <Amount>366.25</Amount> </Stock> </StockDate> <StockDate Day = "03" Month="06" Year="2010"> <Stock> <Symbol>ABC</Symbol> <Amount>110.35</Amount> </Stock> <Stock> <Symbol>XYZ</Symbol> <Amount>369.70</Amount> </Stock> </StockDate> </StockMarket> My approach so far is XDocument doc = new XDocument( new XElement("StockMarket", new XElement("StockDate", new XAttribute("Day", "02"),new XAttribute("Month","06"),new XAttribute("Year","2010")), new XElement("Stock") ) ); Since I am new to Linq to XML, I am presently struggling a lot and henceforth seeking for help. Using C#3.0 . Thanks

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  • Parse particular text from an XML string

    - by Dan Sewell
    Hi all, Im writing an app which reads an RSS feed and places items on a map. I need to read the lat and long numbers only from this string: http://www.xxxxxxxxxxxxxx.co.uk/map.aspx?isTrafficAlert=true&lat=53.647351&lon=-1.933506 .This is contained in link tags Im a bit of a programming noob but im writing this in C#/Silverlight using Linq to XML. Shold this text be extrated when parsing or after parsing and sent to a class to do this? Many thanks for your assistance. EDIT. Im going to try and do a regex on this this is where I need to integrate the regex somewhere in this code. I need to take the lat and long from the Link element and seperate it into two variables I can use (the results are part of a foreach loop that creates a list.) var events = from ev in document.Descendants("item") select new { Title = (ev.Element("title").Value), Description = (ev.Element("description").Value), Link = (ev.Element("link").Value), }; Question is im not quite ure where to put the regex (once I work out how to use the regex properly! :-) )

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  • Refactoring two methods down to one

    - by bflemi3
    I have two methods that almost do the same thing. They get a List<XmlNode> based on state OR state and schoolType and then return a distinct, ordered IEnumerable<KeyValuePair<string,string>>. I know they can be refactored but I'm struggling to determine what type the parameter should be for the linq statement in the return of the method (the last line of each method). I thank you for your help in advance. private IEnumerable<KeyValuePair<string, string>> getAreaDropDownDataSource() { StateInfoXmlDocument stateInfoXmlDocument = new StateInfoXmlDocument(); string schoolTypeXmlPath = string.Format(STATE_AND_SCHOOL_TYPE_XML_PATH, StateOfInterest, ConnectionsLearningSchoolType); var schoolNodes = new List<XmlNode>(stateInfoXmlDocument.SelectNodes(schoolTypeXmlPath).Cast<XmlNode>()); return schoolNodes.Select(x => new KeyValuePair<string, string>(x.Attributes["idLocation"].Value, x.Value)).OrderBy(x => x.Key).Distinct(); } private IEnumerable<KeyValuePair<string, string>> getStateOfInterestDropDownDataSource() { StateInfoXmlDocument stateInfoXmlDocument = new StateInfoXmlDocument(); string schoolTypeXmlPath = string.Format(SCHOOL_TYPE_XML_PATH, ConnectionsLearningSchoolType); var schoolNodes = new List<XmlNode>(stateInfoXmlDocument.SelectNodes(schoolTypeXmlPath).Cast<XmlNode>()); return schoolNodes.Select(x => new KeyValuePair<string, string>(x.Attributes["stateCode"].Value, x.Attributes["stateName"].Value)).OrderBy(x => x.Key).Distinct(); }

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  • Efficient way to call .Sum() on multiple properties

    - by SherCoder
    I have a function that uses Linq to get data from the database and then I call that function in another function to sum all the individual properties using .Sum on each individual property. I was wondering if there is an efficient way to sum all the properties at once rather than calling .Sum() on each individual property. I think the way I am doing as of right now, is very slow (although untested). public OminitureStats GetAvgOmnitureData(int? fnsId, int dateRange) { IQueryable<OminitureStats> query = GetOmnitureDataAsQueryable(fnsId, dateRange); int pageViews = query.Sum(q => q.PageViews); int monthlyUniqueVisitors = query.Sum(q => q.MonthlyUniqueVisitors); int visits = query.Sum(q => q.Visits); double pagesPerVisit = (double)query.Sum(q => q.PagesPerVisit); double bounceRate = (double)query.Sum(q => q.BounceRate); return new OminitureStats(pageViews, monthlyUniqueVisitors, visits, bounceRate, pagesPerVisit); }

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  • Composable FLinq expressions

    - by Daniel
    When doing linq-to-sql in c#, you could do something like this: var data = context.MyTable.Where(x => x.Parameter > 10); var q1 = data.Take(10); var q2 = data.Take(3); q1.ToArray(); q2.ToArray(); This would generate 2 separate SQL queries, one with TOP 10, and the other with TOP 3. In playing around with Flinq, I see that: let data = query <@ seq { for i in context.MyTable do if x.Parameter > 10 then yield i } @> data |> Seq.take 10 |> Seq.toList data |> Seq.take 3 |> Seq.toList is not doing the same thing. Here it seems to do one full query, and then do the "take" calls on the client side. An alternative that I see used is: let q1 = query <@ for i in context.MyTable do if x.Param > 10 then yield i } |> Seq.take 10 @> let q2 = query <@ for i in context.MyTable do if x.Param > 10 then yield i } |> Seq.take 3 @> These 2 generate the SQL with the appropriate TOP N filter. My problem with this is that it doesn't seem composable. I'm basically having to duplicate the "where" clause, and potentially would have to duplicate other other subqueries that I might want to run on a base query. Is there a way to have F# give me something more composable? (I originally posted this question to hubfs, where I have gotten a few answers, dealing with the fact that C# performs the query transformation "at the end", i.e. when the data is needed, where F# is doing that transformation eagerly.)

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  • EF 4 Query - Issue with Multiple Parameters

    - by Brian
    Hello, A trick to avoiding filtering by nullable parameters in SQL was something like the following: select * from customers where (@CustomerName is null or CustomerName = @CustomerName) This worked well for me in LINQ to SQL: string customerName = "XYZ"; var results = (from c in ctx.Customers where (customerName == null || (customerName != null && c.CustomerName == customerName)) select c); But that above query, when in ADO.NET EF, doesn't work for me; it should filter by customer name because it exists, but it doesn't. Instead, it's querying all the customer records. Now, this is a simplified example, because I have many fields that I'm utilizing this kind of logic with. But it never actually filters, queries all the records, and causes a timeout exception. But the wierd thing is another query does something similarly, with no issues. Any ideas why? Seems like a bug to me, or is there a workaround for this? I've since switched to extension methods which works. Thanks.

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  • How to initialize list with parent child relation

    - by user2917702
    Let's say I have the following classes. public class Parent { public string name; IList<Children> children; } public class Child { public string parentName; public int age; } As it is understandable, each parent can have multiple children, and we can have multiple parents. What is the best way to initialize these classes? Is it better to get all of the parents, and all of the children from database then use LINQ? IList<Parent> parents = GetParents()//assume this gets parents from db IList<Child> children = GetChildren() //assume this gets children from db foreach(Parent parent in parents) { parent.children = children.Where(x=>x.parentName==parent.name).ToList(); } or get all of the parents and iterate through each parent to query database by parentName to get children information? Due to requirement that I have, I cannot use datatable or dataset; I can only use datareader. IList<Parent> parents = GetParents()//assume this gets parents from db foreach(Parent parent in parents) { parent.children = GetChildrenByParentName();//assume this gets parents from db by parentName } Thank you

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  • How to break an object into chunks based on some property?

    - by CurlyFro
    public class InvestorMailing { public string To { get; set; } public IEnumerable<string> Attachments { get; set; } public int AttachmentCount { get; set; } public long AttachmentSize { get; set; } } i have an IList<InvestorMailing> mailingList. if the attachment size is greater than x, then i need to split my object into chunks. is there an easy linq-y way to do this? Edited: this is how i'm generating my mailings: var groupedMailings = mailingList.GroupBy(g => g.GroupBy); var investorMailings = groupedMailings.Select( g => new DistinctInvestorMailing { Id = g.Select(x => x.Id).FirstOrDefault(), To = g.Key.Trim(), From = g.Select(x => x.From).FirstOrDefault(), FromName = g.Select(x => x.FromName).FirstOrDefault(), Bcc = g.Select(x => x.Bcc).FirstOrDefault(), DeliveryCode = g.Select(x => x.DeliveryCode).FirstOrDefault(), Subject = g.Select(x => x.Subject).FirstOrDefault(), Body = g.Select(x => x.Body).FirstOrDefault(), CommentsOnStatus = g.Select(x => x.CommentsOnStatus).FirstOrDefault(), Attachments = g.Select(x => x.AttachmentPath), AttachmentCount = g.Select(x => x.AttachmentPath).Count(), AttachmentSize = g.Sum(x => x.AttachmentSize), MailType = g.Select(x => x.MessageType).FirstOrDefault() } ).ToList();

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  • A good(elegant) way to retrieve records with counts.

    - by user93422
    Context: ASP.NET MVC 2.0, C#, SQL Server 2007, IIS7 I have 'scheduledMeetings' table in the database. There is a one-to-many relationship: scheduledMeeting - meetingRegistration So that you could have 10 people registered for a meeting. meetingRegistration has fields Name, and Gender (for example). I have a "calendar view" on my site that shows all coming events, as well as gender count for each event. At the moment I use Linq to Sql to pull the data: var meetings = db.Meetings.Select( m => new { MeetingId = m.Id, Girls = m.Registrations.Count(r => r.Gender == 0), Boys = m.Registrations.Count(r=>r.Gender == 1) }); (actual query is half-a-page long) Because there is anonymous type use going on I cant extract it into a method (since I have several different flavors of calendar view, with different information on each, and I dont want to create new class for each). Any suggestions on how to improve this? Is database view is the answer? Or should I go ahead and create named-type? Any feedback/suggestions are welcome. My DataLayer is huge, I want to trim it, just dont know how. Pointers to a good reading would be good too.

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  • How to convert object to string list?

    - by user1381501
    I want to get two values by using linq select query and try to convert object to string list. I am trying to convert list to list. The code as below. I got the error when I convert object to string list : return returnvalue = (List)userlist; public List<string> GetUserList(string username) { List<User> UserList = new List<User>(); List<string> returnvalue=new List<string>(); try { string returnstring = string.Empty; DataTable dt = null; dt = Library.Helper.FindUser(username, 200); foreach (DataRow dr in dt.Rows) { User user = new User(); spuser.id = dr["ID"].ToString(); spuser.name = dr["Name"].ToString(); UserList.Adduser } } catch (Exception ex) { } List<SharePointMentoinUser> userlist = UserList.Select(a => new User { name = (string)a.name, id = (string)a.id }).ToList(); **return returnvalue = (List<string>)userlist;** }

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  • List of running minimum values

    - by scarle88
    Given a sorted list of: new []{1, 2, -1, 3, -2, 1, 1, 2, -1, -3} I want to be able to iterate over the list and at each element return the smallest value iterated so far. So given the list above the resultant list would look like: 1 1 -1 -1 -2 -2 -2 -2 -2 -3 My rough draft code looks like: var items = new []{1, 2, -1, 3, -2, 1, 1, 2, -1, -3}; var min = items.First(); var drawdown = items.Select(i => { if(i < min) { min = i; return i; } else { return min; } }); foreach(var i in drawdown) { Console.WriteLine(i); } But this is not very elegant. Is there an easier to read (linq?) way of doing this? I looked into Aggregate but it seemed to be the wrong tool. Ultimately the list of items will be very long, in the many thousands. So good performance will be an issue to.

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  • LINQ to Entities Projection of Nested List

    - by Matthew
    Assuming these objects... class MyClass { int ID {get;set;} string Name {get;set;} List<MyOtherClass> Things {get;set;} } class MyOtherClass { int ID {get;set;} string Value {get;set;} } How do I perform a LINQ to Entities Query, using a projection like below, that will give me a List? This works fine with an IEnumerable (assuming MyClass.Things is an IEnumerable, but I need to use List) MyClass myClass = (from MyClassTable mct in this.Context.MyClassTableSet select new MyClass { ID = mct.ID, Name = mct.Name, Things = (from MyOtherClass moc in mct.Stuff where moc.IsActive select new MyOtherClass { ID = moc.ID, Value = moc.Value }).AsEnumerable() }).FirstOrDefault(); Thanks in advance for the help!

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  • split a list using linq

    - by Anonym
    I've the following code: var e = someList.GetEnumerator(); var a = new List<Foo>(); var b = new List<Foo>(); while(e.MoveNext()) { if(CheckCondition(e.Current)) { b.Add(e.Current); break; } a.Add(e.Current); } while(e.MoveNext()) b.Add(e.Current) This looks ugly. Basically, iterate through a list and add elements to one list until some condition kicks in, and add the rest to another list. Is there a better way e.g. using linq ? CheckCondition() is expensive, and the lists can be huge so I'd prefer to not do anything that iterates the lists twice.

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  • exception with Linq to SQL using sdf file

    - by Ben
    Hi, I've set up a project with an SDF local database file and am trying to access it using an LINQ To SQL (".dbml") file. I have used the connection string provided by the sdf file and can instanciate the object with out a problem: thisDataContext = new MyDataContext(GetConnectionString()); However, whenever i try to access any information from it eg var collection = (from MyObject p in thisDataContext.MyTable select p); I get the error - "The table name is not valid. [ Token line number (if known) = 2,Token line offset (if known) = 14,Table name = Person ]" I am using Visual Studio 2008 SP1 .Net 3.5 and SQL 2008 CE. I gather something similar happened for SQL 2005 CE and a Hotfix was released, but i would have thought the fix would have been fixed in this version before release. Does anyone know the fix for this? Thanks

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  • linq Except and custom IEqualityComparer

    - by Joe
    I'm trying to implement a custom comparer on two lists of strings and use the .Except() linq method to get those that aren't one one of the lists. The reason I'm doing a custom comparer is because I need to do a "fuzzy" compare, i.e. one string on one list could be embedded inside a string on the other list. I've made the following comparer ` public class ItemFuzzyMatchComparer : IEqualityComparer { bool IEqualityComparer<string>.Equals(string x, string y) { return (x.Contains(y) || y.Contains(x)); } int IEqualityComparer<string>.GetHashCode(string obj) { if (Object.ReferenceEquals(obj, null)) return 0; return obj.GetHashCode(); } } ` When I debug, the only breakpoint that hits is in the GetHashCode() method. The Equals() never gets touched. Any ideas?

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  • Listing subdirectories 3 levels deep using LINQ C#

    - by paradox
    I'd like to know if there is a better alternative to my following code (preferably using LINQ) #region List and filter directories to only 3 levels deep // List all subdirectories within main directory string[] folders = Directory.GetDirectories(@"C:\pdftest\", "*" ,SearchOption.AllDirectories); List<string> subdirectories = new List<string>(); //Filter away all main directories, now we are left with subdirectories 3 levels deep for (int i = 0; i<folders.Length; i++) { int occurences = folders[i].Split('\\').Length-1; if (occurences==4) subdirectories.Add(folders[i]); } #endregion

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  • dotConnect LINQ to MySQL Issue

    - by Saravanan I M
    I am using dotConnect LINQ to MySQL and i have the following error. what would be the cause for this issue annot convert parameter value of type 'System.String' to MySQL type 'MySqlType.TimeStamp'. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidCastException: Cannot convert parameter value of type 'System.String' to MySQL type 'MySqlType.TimeStamp'. Source Error: Line 93: { Line 94: string loginLowered = login.ToLower(); Line 95: return context.ISVs.Where(u = u.Email == loginLowered).SingleOrDefault() == null; Line 96: Line 97: }

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  • ASP.NET MVC2 - using LINQ-generated class

    - by ile
    There are few things not clear to me about ASP.NET MV2. In database I have table Contacts with several fields, and there is an additional field XmlFields of which type is xml. In that field are stored additional description fields. There are 4 classes: Contact class which corresponds to Contact table and is defined by default when creating LINQ classes ContactListView class which inherits Contact class and has some additional properties ContactXmlView class that contains fields from XmlFields field ContactDetailsView class which merges ContactListView and ContactXmlView into one class and this one is used to display data in view pages ContactListView class has re-defined some properties from Contact class (so that I can add [Required] filter used for validation) - but I get warning message: 'ObjectTest.Models.Contacts.ContactListView.FirstName' hides inherited member 'SA.Model.Contact.FirstName'. Use the new keyword if hiding was intended. ContactDetailsView class is also used in a form when creating new contact and adding it to database. I am not sure if this is correct way, and the warning message confuses me a bit. Any advise about this? Thanks, Ile

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  • NHibernate.Linq to Criteria API translation help needed

    - by Arnis L.
    I'm not sure how to add paging to this: Session.Linq<Article>() .Where(art => art.Tags.Any(t => t.Name == tag)).ToList(). So i decided to use Criteria API. var rowCount = Session.CreateCriteria(typeof(Article)) .SetProjection(Projections.RowCount()).FutureValue<Int32>(); var res = Session.CreateCriteria(typeof(Article)) .Add(/* any help with this? :) */) .SetFirstResult(page * pageSize) .SetMaxResults(pageSize) .AddOrder(new Order("DatePublish", true)) .Future<Article>(); totalCount = rowCount.Value; Any help appreciated.

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  • Subsonic linq using activerecord very slow compared to simplerepository

    - by skiik
    Anyone know anything about why linq queries are about 6 times slower when querying using active record vs simplerepository? The below code runs 6 times slower than when i query the data using a simple repository. This code is executed 1000 times in a loop Thanks in advance string ret = ""; // if (plan == null) { plan =VOUCHER_PLAN.SingleOrDefault(x => x.TENDER_TYPE == tenderType); } if (plan == null) throw new InvalidOperationException("voucher type does not exist." + tenderType); seq = plan.VOUCHER_SEQUENCES.First(); int i = seq.CURRENT_NUMBER; seq.CURRENT_NUMBER += seq.STEP; seq.Save();

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  • Can't Add LINQ to SQL classes to projects in VS2010

    - by MisterJames
    I just ran into something in Visual Studio 2010 RC that wasn't previously happening (like, yesterday). No software changes here, but I did run into some muck yesterday when compiling that required a reboot. I am unable to add LINQ to SQL classes to any project through the add dialog. I have created ASP.NET web sites, ASP.NET MVC projects - both of these as 'templated' and as 'empty' - and there appear to be no templates installed or available. I have made sure that the project targets the 4.0 Framework. I can easily add a new database and the ADO.NET entity framework templates are there. As a workaround I can copy a DBML file to my project, delete all tables and sprocs, update the connection string and use the leftover shell (the designer works fine like this), but it's a pain. Has anyone else had their templates drop? Figured out how to reinstall them?

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  • Any clever way to fix 'string or binary data would be truncated' warning with LINQ

    - by Simon_Weaver
    Is there a clever way to determine which field is causing 'string or binary data would be truncated' with LINQ. I've always ended up doing it manually by stepping through a debugger, but with a batch using 'SubmitChanges' I have to change my code to inserting a single row to find the culprit in a batch of rows. Am I missing something or in this day and age do I really have to still use a brute force method to find the problem. Please dont give me advice on avoiding this error in future (unless its something much cleverer than 'validate your data'). The source data is coming from a different system where I dont have full control anyway - plus I want to be lazy. PS. Does SQL Server 2008 actually tell me the field name. Please tell me it does! I'll upgrade!

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