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  • field<t> invalid cast

    - by Zwempha
    I'm having problems when using linq on a datatable.asenumerable(). This throws InvalidCastException. DateTime date=r.Field<DateTime>("date"); This works fine. DateTime date = DateTime.Parse(r.Field<string>("date")); What am I missing? Regards Sven

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  • What does DataContext.GetTable<TEntry> do?

    - by Bryan
    Consider I have a DataContext db, and there is an Entity class User. So when System.Data.Linq.Table<User> table = db.GetTable<User>(); is called for the first time, does it pull the data from the database immediately, does it use deferred execution, or were the data already loaded from database when db was initialized?

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  • Does Table.InsertOnSubmit create a copy of the original table?

    - by Bryan
    Using InsertOnSubmit seems to have some memory overhead. I have a System.Data.Linq.Table<User> table. When I do table.InsertOnSubmit(user) and then int count = table.Count(), the memory usage of my application increases by roughly the size of the User table, but the count is the number of items before user was inserted. So I'm guess an enumeration after InsertOnSubmit will create a copy of the table. Is that true?

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  • Store an image in a SQL Server CE database

    - by Vaccano
    Does any one know of an example on how to store an image in a SQL Server CE database? What data type should the column be? (I am guessing binary.) I use Linq-To-Datasets. Is it possible using that to put the image into the database and pull it out again later? Thanks for any advice.

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  • Repository Pattern: SaveOrUpdate() in Entity Framework and L2S

    - by JMSA
    These web articles uses separate Save() and Update() methods in the repository pattern. I am using repository pattern. How can I write a SaveOrUpdate() method in Entity Framework with the help of ObjectContext and in Linq-To-SQL with the help of DataContext? That is, how can I write a single method that shall do both save and update job?

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  • Most suitable collection for multithreading requests?

    - by Raj Aththanayake
    I have ~10,000 records would like to keep in a collection in memory and execute LINQ queries against it. This collection should be available for all the users in the application domain and can access concurrently. I’m looking for a .NET collection that supports multithreading can query asynchronously and efficiently without any threading issues. Any suggestions on deciding a collection for this?

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  • Cannot convert lamda expression

    - by Kirsty White
    If I try: Groups = students.Remove(f => f.StudentID.Equals(studentID)); I get an error on this line: f => f.StudentID.Equals(studentID) I am having difficulty from my previous posts here linq deleted users still associated with groups and here Delete method in WCF So I thought maybe I could delete the students contained within groups but I get an error Cannot convert lamda expression to type Student because it is not a delegate type.

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  • c# Lambda Expression built with LinqKit does not compile

    - by Frank Michael Kraft
    This lambda does not compile, but I do not understand why. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Linq.Expressions; using LinqKit; namespace ConsoleApplication2 { class Program { static void Main(string[] args) { var barModel = new BarModel(); string id = "some"; Console.WriteLine(barModel.subFor(id).ToString()); // output: m => (True AndAlso (m.key == value(ConsoleApplication2.Bar`1+<>c__DisplayClass0[ConsoleApplication2.Model]).id)) Console.ReadKey(); var subworkitems = barModel.list.Where(barModel.subFor(id).Compile()); // Exception {"variable 'm' of type 'ConsoleApplication2.Model' referenced from scope '', but it is not defined"} Console.WriteLine(subworkitems.ToString()); Console.ReadKey(); } } class Bar<TModel> { public Bar(Expression<Func<TModel, string>> foreignKeyExpression) { _foreignKeyExpression = foreignKeyExpression; } private Expression<Func<TModel, string>> _foreignKeyExpression { get; set; } public Expression<Func<TModel, bool>> subFor(string id) { var ex = forTargetId(id); return ex; } public Expression<Func<TModel, bool>> forTargetId(String id) { var fc = _foreignKeyExpression; Expression<Func<TModel, bool>> predicate = m => true; var result = predicate.And(m => fc.Invoke(m) == id).Expand(); return result; } } class Model { public string key; public string value; } class BarModel : Bar<Model> { public List<Model> list; public BarModel() : base(m => m.key) { list = new List<Model>(); } } }

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  • Looping over ILookup, accessing values

    - by Jono
    I've got a ILookup< string, List<CustomObject> > from some linq I've done. I'd like to now iterate over the results: foreach(IGrouping<string, List<CustomObject>> groupItem in lookupTable) { groupItem.Key; //You can access the key, but not the list of CustomObject } I know I must be misrepresenting a IGrouping as a KeyValuePair, but now I'm not sure how to access it properly.

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  • Cast IEnumerable<Inherited> To IEnumerable<Base>

    - by david2342
    I'm trying to cast an IEnumerable of an inherited type to IEnumerable of base class. Have tried following: var test = resultFromDb.Cast<BookedResource>(); return test.ToList(); But getting error: You cannot convert these types. Linq to Entities only supports conversion primitive EDM-types. The classes involved look like this: public partial class HistoryBookedResource : BookedResource { } public partial class HistoryBookedResource { public int ResourceId { get; set; } public string DateFrom { get; set; } public string TimeFrom { get; set; } public string TimeTo { get; set; } } public partial class BookedResource { public int ResourceId { get; set; } public string DateFrom { get; set; } public string TimeFrom { get; set; } public string TimeTo { get; set; } } [MetadataType(typeof(BookedResourceMetaData))] public partial class BookedResource { } public class BookedResourceMetaData { [Required(ErrorMessage = "Resource id is Required")] [Range(0, int.MaxValue, ErrorMessage = "Resource id is must be an number")] public object ResourceId { get; set; } [Required(ErrorMessage = "Date is Required")] public object DateFrom { get; set; } [Required(ErrorMessage = "Time From is Required")] public object TimeFrom { get; set; } [Required(ErrorMessage = "Time to is Required")] public object TimeTo { get; set; } } The problem I'm trying to solve is to get records from table HistoryBookedResource and have the result in an IEnumerable<BookedResource> using Entity Framework and LINQ. UPDATE: When using the following the cast seams to work but when trying to loop with a foreach the data is lost. resultFromDb.ToList() as IEnumerable<BookedResource>; UPDATE 2: Im using entity frameworks generated model, model (edmx) is created from database, edmx include classes that reprecent the database tables. In database i have a history table for old BookedResource and it can happen that the user want to look at these and to get the old data from the database entity framework uses classes with the same name as the tables to receive data from db. So i receive the data from table HistoryBookedResource in HistoryBookedResource class. Because entity framework generate the partial classes with the properties i dont know if i can make them virtual and override. Any suggestions will be greatly appreciated.

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  • group object with equal collections

    - by Jeroen
    Hi, Suppose 2 classes, Person and Pet. Each person has a collection of 1 or more pets. How do i group the Person in to a collection where they share the same pets. Example: Person 1: Cat, Dog, Spider Person 2: Cat, Spider, Snake Person 3: Dog Person 4: Spider, Cat, Dog Person 5: Dog What i want as a result is this: Group 1: Person 1, Person 4 Group 2: Person 3, Person 5 Group 3: Person 2 How do i achieve this using LINQ?

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  • Foreign Keys Duplicated in DataGridView

    - by John Doe
    I created a Windows Forms Application to which I added a DataGridView and LINQ to SQL Classes from one of my databases. I can successfully bind one of my database's tables to my DataGridView: var dataSource = from c in _db.NetworkedEquipments select c; dataGridView1.DataSource = dataSource; However, the foreign keys get duplicated, that is, the columns appear twice. How can I prevent this?

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  • How do I use a concatenation of 2 columns in a SQL DB in ASP.NET properly?

    - by user293357
    I'm using LinqToSql like this with a CheckBoxList in ASP.NET: var teachers = from x in dc.teachers select x; cbl.DataSource = teachers; cbl.DataTextField = "name"; cbl.DataValueField = "teacherID"; cbl.DataBind(); I want to display both "firstname" and "name" in the DataTextField however. I found this solution but I'm using LINQ: http://stackoverflow.com/questions/839223/concatenate-two-fields-in-a-dropdown How do I do this?

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  • How to get an array of members of an array

    - by Mystere Man
    Suppose I have a class public class Foo { public Bar { get; set; } } Then I have another class public class Gloop { public List<Foo> Foos { get; set; } } What's the easiest way to get a List of Foo.Bars? I'm using C# 4.0 and can use Linq if that is the best choice. My first thought was something like

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  • How to convert a 2-d array into a dictionary object

    - by Nikron
    Hi, I have an array of type string that looks like this: "test1|True,test2|False,test3|False,test4|True". This is essentially a 2d array like so [test1][True] [test2][False] [test3][False] [test4][True]. I want to convert this into a dictionary<string,bool> using linq, something like: Dictionary<string, bool> myResults = results.Split(",".ToCharArray).ToDictionary() any ideas?

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  • C# Check for missing number in sequence

    - by Jon
    I have an List<int> which contains 1,2,4,7,9 for example. I have a range from 0 to 10. Is there a way to determine what numbers are missing in that sequence? I thought LINQ might provide an option but I can't see one In the real world my List could contain 100,000 items so performance is key

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  • Show Detailed Error in SQL Profiler

    - by AlwaysBeCoding
    Is there any way showing the detailed exception for String or binary data would be truncated. I use LINQ to SQL and i cant figure out which column is that!? Tried numerous things but i get the same meaningless error i got from within Visual Studio. Also I use .NET 3.5 SP1, but errors are still returned useless.

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