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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Alternatives of Datatable

    - by mavera
    In my web application, I have a dynamic query that returns huge data to datatable, and this query is often recalled with different parameters. So database is exhausted. I want to get all record with no parameters to an object, and perform queries (may be with linq) on this object. So database will not be exthausted. Which objects can be used instead of datatable?

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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 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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  • Foreach loop problem for Iqueyable object

    - by Vikas
    Hi, Can we use foreach loop for Iqueryable object? I'd like to do something as follow: query = Iqueryable<Myclass> = objDataContext.Myclass; // objDataContext is an object of LINQ datacontext class int[] arr1 = new int[] { 3, 4, 5 }; foreach (int i in arr1) { query = query.Where(q => (q.f_id1 == i || q.f_id2 == i || q.f_id3 == i)); } It gives me wrong output as each time value if i is changed.

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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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  • 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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  • Using Joins vs Entity associations

    - by shivesh
    I am learning Entity framework and linq-to-entities. It's possible to get cross values from multiple tables using JOINS (join keyword) or using the navigation fields ( associations) in which case the framework knows how to reference the cross data. My question is what to use when?

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  • does @@identity return the primary key or identity field?

    - by elspiko
    Hi, My issue is that I've got update triggers on an SQL View (MS SQL 2005) which I'm mapping to LINQ to SQL entities in C#... My SQL looks correct but it complains about trying to insert a null value into a secondary table PK field. I believe my issue relates to having the primary key and identity as seperate fields in the primary table. So my question is this....when using @@identity, does it look at the primary key of the inserted row, or does it look at the field with "IDENTITY" specified???

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