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  • Using linq to combine objects

    - by DotnetDude
    I have 2 instances of a class that implements the IEnumerable interface. I would like to create a new object and combine both of them into one. I understand I can use the for..each to do this. Is there a linq/lambda expression way of doing this?

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  • Dynamic LINQ OrderBy

    - by John Sheehan
    I found an example in the VS2008 Examples for Dynamic LINQ that allows you to use a sql-like string (e.g. OrderBy("Name, Age DESC")) for ordering. Unfortunately, the method included only works on IQueryable<T>. Is there any way to get this functionality on IEnumerable<T>?

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  • How to group a serial of objects according to timestamp

    - by Benny
    I have a serial of object defined as: public class Foo { public DateTime Time {get;set;} } now I want to group objects(IEnumerable<Foo>) according to the time, e.g. I want to group them according to hour or day or month. for example (group into hour): group 1(13:00-14:00) : foo1, foo2, foo3 group 2(14:00-15:00): foo4, foo5 How to write LINQ? hope I made myself clear.

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  • MVVM/WPF: Using a ObservableCollection<T> as a list in a domain model, is that good/bad ?

    - by msfanboy
    I have aggregated models like Customer:Order:Product. As my View is bound to the BillingViewModel which has a Property Customers of type ObservableCollection and ONE customer in this collection has a "list" of orders named ObservableCollection and ONE order in this collection has a "list" of products named ObservableCollection Well I need the ObservableCollection`s for databinding but should a domain model really have a ObservableCollection ? normally it has a List or IEnumerable ! Is this bad habit or having side effects?

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  • EF Query Object Pattern over Repository Example

    - by Dale Burrell
    I have built a repository which only exposes IEnumerable based mostly on the examples in "Professional ASP.NET Design Patterns" by Scott Millett. However because he mostly uses NHibernate his example of how to implement the Query Object Pattern, or rather how to best translate the query into something useful in EF, is a bit lacking. I am looking for a good example of an implementation of the Query Object Pattern using EF4.

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  • C# - How to override GetHashCode with Lists in object

    - by Christian
    Hi, I am trying to create a "KeySet" to modify UIElement behaviour. The idea is to create a special function if, eg. the user clicks on an element while holding a. Or ctrl+a. My approach so far, first lets create a container for all possible modifiers. If I would simply allow a single key, it would be no problem. I could use a simple Dictionary, with Dictionary<Keys, Action> _specialActionList If the dictionary is empty, use the default action. If there are entries, check what action to use depending on current pressed keys And if I wasn't greedy, that would be it... Now of course, I want more. I want to allow multiple keys or modifiers. So I created a wrapper class, wich can be used as Key to my dictionary. There is an obvious problem when using a more complex class. Currently two different instances would create two different key, and thereby he would never find my function (see code to understand, really obvious) Now I checked this post: http://stackoverflow.com/questions/638761/c-gethashcode-override-of-object-containing-generic-array which helped a little. But my question is, is my basic design for the class ok. Should I use a hashset to store the modifier and normal keyboardkeys (instead of Lists). And If so, how would the GetHashCode function look like? I know, its a lot of code to write (boring hash functions), some tips would be sufficient to get me started. Will post tryouts here... And here comes the code so far, the Test obviously fails... public class KeyModifierSet { private readonly List<Key> _keys = new List<Key>(); private readonly List<ModifierKeys> _modifierKeys = new List<ModifierKeys>(); private static readonly Dictionary<KeyModifierSet, Action> _testDict = new Dictionary<KeyModifierSet, Action>(); public static void Test() { _testDict.Add(new KeyModifierSet(Key.A), () => Debug.WriteLine("nothing")); if (!_testDict.ContainsKey(new KeyModifierSet(Key.A))) throw new Exception("Not done yet, help :-)"); } public KeyModifierSet(IEnumerable<Key> keys, IEnumerable<ModifierKeys> modifierKeys) { foreach (var key in keys) _keys.Add(key); foreach (var key in modifierKeys) _modifierKeys.Add(key); } public KeyModifierSet(Key key, ModifierKeys modifierKey) { _keys.Add(key); _modifierKeys.Add(modifierKey); } public KeyModifierSet(Key key) { _keys.Add(key); } }

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  • Custom Collection Initializers

    - by Jake
    Classes that implement IEnumerable and provide a public void Add(/* args */) function can be initialized like in the following example: List<int> numbers = new List<int>{ 1, 2, 3 }; which calls the Add(int) function 3x after initializing the List<int>. Is there a way to define this behavior explicitly for my own classes? For example, could I have the initializer call a function other than the appropriate Add() overload?

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  • NHibernate - I have many, but I only want one!

    - by MartinF
    Hello, I have a User which can have many Emails. This is mapped through a List collection (exposed by IEnumerable Emails on the User). For each User one of the Emails will be the Primary one ("Boolean IsPrimary" property on Email). How can I get the primary Email from User without NHibernate loads every email for the User ? I have the following two entities, with a corresponding table for each public class User { public virtual int Id { get; set; } public virtual IEnumerable<Email> Emails { get; set; } // public virtual Email PrimaryEmail { get; set; } - Possible somehow ? } public class Email { public virtual int Id { get; set; } public virtual String Address { get; set; } public virtual Boolean IsPrimary { get; set; } public virtual User User { get; set; } } Can I map a "Email PrimaryEmail" property etc. on the User to the Email which have "IsPrimary=1" set somehow ? Maybe using a Sql Formula ? a View ? a One-To-One relationship ? or another way ? It should be possible to change the primary email to be one of the other emails, so i would like to keep them all in 1 table and just change the IsPrimary property. Using a Sql Formula, is it be possible to keep the "PrimaryEmail" property on the User up-to-date, if I set the IsPrimary property on the current primary email to false, and then afterwards set the PrimaryEmail property to the email which should be the new primary email and set IsPrimary to true ? Will NHibernate track changes on the "old/current" primary Email loaded by the Sql Formula ? What about the 1 level cache and the 2 level cache when using SqlFormula ? I dont know if it could work by using a View ? Then i guess the Email could be mapped like a Component ? Will it work when updating the Email data when loaded from the View ? Is there a better way ? As I have a bi-directional relationship between User and Email I could in many cases of course query the primary Email and then use the "User" property on the Email to get the User (instead of the other way around - going from User to the primary Email) Hope someone can help ?

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  • .NET - Very strange NullReferenceException?

    - by ropstah
    How can I get a NullReferenceException in the following scenario? Dim langs As IEnumerable(Of SomeCustomObject) = //some LINQ query If langs Is Nothing Then Return Nothing If langs.Count = 1 Then //NullReferenceException here What am I missing here? Debug shows that langs is really just a LINQ queryresult without any results...

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  • State machines in C#

    - by Sir Psycho
    Hi, I'm trying to work out what's going on with this code. I have two threads iterating over the range and I'm trying to understand what is happening when the second thread calls GetEnumerator(). This line in particular (T current = start;), seems to spawn a new 'instance' in this method by the second thread. Seeing that there is only one instance of the DateRange class, I'm trying to understand why this works. Thanks in advance. class Program { static void Main(string[] args) { var daterange = new DateRange(DateTime.Now, DateTime.Now.AddDays(10), new TimeSpan(24, 0, 0)); var ts1 = new ThreadStart(delegate { foreach (var date in daterange) { Console.WriteLine("Thread " + Thread.CurrentThread.ManagedThreadId + " " + date); } }); var ts2 = new ThreadStart(delegate { foreach (var date in daterange) { Console.WriteLine("Thread " + Thread.CurrentThread.ManagedThreadId + " " + date); } }); Thread t1 = new Thread(ts1); Thread t2 = new Thread(ts2); t1.Start(); Thread.Sleep(4000); t2.Start(); Console.Read(); } } public class DateRange : Range<DateTime> { public DateTime Start { get; private set; } public DateTime End { get; private set; } public TimeSpan SkipValue { get; private set; } public DateRange(DateTime start, DateTime end, TimeSpan skip) : base(start, end) { SkipValue = skip; } public override DateTime GetNextElement(DateTime current) { return current.Add(SkipValue); } } public abstract class Range<T> : IEnumerable<T> where T : IComparable<T> { readonly T start; readonly T end; public Range(T start, T end) { if (start.CompareTo(end) > 0) throw new ArgumentException("Start value greater than end value"); this.start = start; this.end = end; } public abstract T GetNextElement(T currentElement); public IEnumerator<T> GetEnumerator() { T current = start; do { Thread.Sleep(1000); yield return current; current = GetNextElement(current); } while (current.CompareTo(end) < 1); } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return GetEnumerator(); } }

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  • Examples of useful or non-trival dual interfaces

    - by Scott Weinstein
    Recently Erik Meijer and others have show how IObservable/IObserver is the dual of IEnumerable/IEnumerator. The fact that they are dual means that any operation on one interface is valid on the other, thus providing a theoretical foundation for the Reactive Extentions for .Net Do other dual interfaces exist? I'm interested in any example, not just .Net based.

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  • To Reference A Generic Method With A Lambda Expression

    - by SDReyes
    It is possible to reference a generic method using a Lambda Expression Object? For example, having: TheObject: public abstract class LambdaExpression : Expression TheMethod (an extension method of LINQ): public static TSource Last<TSource>( this IEnumerable<TSource> source ) I'm trying to create an instance of TheObject, that references to TheMethod. How do you do such thing?

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  • Synchronizing thread communication?

    - by Roger Alsing
    Just for the heck of it I'm trying to emulate how JRuby generators work using threads in C#. Also, I'm fully aware that C# haas built in support for yield return, I'm just toying around a bit. I guess it's some sort of poor mans coroutines by keeping multiple callstacks alive using threads. (even though none of the callstacks should execute at the same time) The idea is like this: The consumer thread requests a value The worker thread provides a value and yields back to the consumer thread Repeat untill worker thread is done So, what would be the correct way of doing the following? //example class Program { static void Main(string[] args) { ThreadedEnumerator<string> enumerator = new ThreadedEnumerator<string>(); enumerator.Init(() => { for (int i = 1; i < 100; i++) { enumerator.Yield(i.ToString()); } }); foreach (var item in enumerator) { Console.WriteLine(item); }; Console.ReadLine(); } } //naive threaded enumerator public class ThreadedEnumerator<T> : IEnumerator<T>, IEnumerable<T> { private Thread enumeratorThread; private T current; private bool hasMore = true; private bool isStarted = false; AutoResetEvent enumeratorEvent = new AutoResetEvent(false); AutoResetEvent consumerEvent = new AutoResetEvent(false); public void Yield(T item) { //wait for consumer to request a value consumerEvent.WaitOne(); //assign the value current = item; //signal that we have yielded the requested enumeratorEvent.Set(); } public void Init(Action userAction) { Action WrappedAction = () => { userAction(); consumerEvent.WaitOne(); enumeratorEvent.Set(); hasMore = false; }; ThreadStart ts = new ThreadStart(WrappedAction); enumeratorThread = new Thread(ts); enumeratorThread.IsBackground = true; isStarted = false; } public T Current { get { return current; } } public void Dispose() { enumeratorThread.Abort(); } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { if (!isStarted) { isStarted = true; enumeratorThread.Start(); } //signal that we are ready to receive a value consumerEvent.Set(); //wait for the enumerator to yield enumeratorEvent.WaitOne(); return hasMore; } public void Reset() { throw new NotImplementedException(); } public IEnumerator<T> GetEnumerator() { return this; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this; } } Ideas?

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  • What is the minimum interface that has the Count property in .Net

    - by SoMoS
    Hello, I need to change a method that has one parameter that takes a serie of objects. I need to find the lowest Interface (in inheritance tree) that has the Count property. Until now I was using the IEnumerable but as this has not Count I need to change it to the wider interface possible so the method can work with the biggest number of types of series (collections, lists, arrays, etc). Thanks in advance.

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  • Please Explain .NET Delegates

    - by user275561
    So I read MSDN and Stack Overflow. I understand what the Action Delegate does in general but it is not clicking no matter how many examples I do. In general, the same goes for the idea of delegates. So here is my question. When you have a function like this: public GetCustomers(Action<IEnumerable<Customer>,Exception> callBack) { } What is this, and what should I pass to it?

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  • Why doesn't XmlSerializer support Dictionary?

    - by theburningmonk
    Just curious as to why Dictionary is not supported by XmlSerializer? You can get around it easily enough by using DataContractSerializer and writing the object to a XmlTextWriter, but what are the characteristics of a Dictionary that makes it difficult for a XmlSerializer to deal with considering it's really an array of KeyValuePairs. In fact, you can pass an IDictionary<TKey, TItem> to a method expecting an IEnumerable<KeyValuePairs<TKey, ITem>>.

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  • linq groupby in strongly typed MVC View

    - by jason
    How do i get an IGrouping result to map to the view? I have this query: var groupedManuals = manuals.GroupBy(c => c.Series); return View(groupedManuals); What is the proper mapping for the ViewPage declaration? Inherits="System.Web.Mvc.ViewPage<IEnumerable<ProductManual>>"

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  • Ninject with Object Initializers and LINQ

    - by Alexander Kahoun
    I'm new to Ninject so what I'm trying may not even be possible but I wanted to ask. I free-handed the below so there may be typos. Let's say I have an interface: public interface IPerson { string FirstName { get; set; } string LastName { get; set;} string GetFullName(); } And a concrete: public class Person : IPerson { public string FirstName { get; set; } public string LastName { get; set; } public string GetFullName() { return String.Concat(FirstName, " ", LastName); } } What I'm used to doing is something like this when I'm retrieving data from arrays or xml: public IEnumerable<IPerson> GetPeople(string xml) { XElement persons = XElement.Parse(xml); IEnumerable<IPerson> people = ( from person in persons.Descendants("person") select new Person { FirstName = person.Attribute("FName").Value, LastName = person.Attribute("LName").Value }).ToList(); return people; } I don't want to tightly couple the concrete to the interface in this manner. I haven't been able to find any information in regards to using Ninject with LINQ to Objects or with object initializers. I may be looking in the wrong places, but I've been searching for a day now with no luck at all. I was contemplating putting the kernel into an singleton instance and seeing if that would work, but I'm not sure that it will plus I've heard that passing your kernel around is a bad thing. I'm trying to implement this in a class library currently. If this is not possible, does anyone have any examples or suggestions as to what the best practice is in this case? Thanks in advance for the help. EDIT: Based on some of the answers I feel I should clarify. Yes, the example above appears short lived but it was simply an example of one piece that I was trying to do. Let's give a bigger picture. Say instead of XML I am gathering all my data through a 3rd party web service and I'm creating an interface for it, the data could be a defined object in the wsdl or it could sometimes be an xml string. IPerson could be used for both the Person object and a User object. I will be doing this inside of a separate class library, because it needs to be portable and will be used in other projects, and handing it to an MVC3 Web Application and the objects will be used in javascript as well. I appreciate all the input so far.

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  • LINQ to group objects according to timestamp

    - by Benny
    I have a serial of object defined as: public class Foo { public DateTime Time {get;set;} } now I want to group objects(IEnumerable<Foo>) according to the time, e.g. I want to group them according to hour or day or month. for example (group into hour): group 1(13:00-14:00) : foo1, foo2, foo3 group 2(14:00-15:00): foo4, foo5 How to write LINQ over this? hope I made myself clear.

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  • Get selected value of dropdownlist in asp.net MVC

    - by Xulfee
    how can i get select value of dropdownlist and here is my code which is working fine. var list = new[] { new Person { Id = 1, Name = "Name1" }, new Person { Id = 2, Name = "Name2" }, new Person { Id = 3, Name = "Name3" } }; var selectList = new SelectList(list, "Id", "Name", 2); ViewData["People"] = selectList; <%= Html.DropDownListFor(model => model.Peoples, ViewData["People"] as IEnumerable<SelectListItem>)%>

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  • C# mvc 3 using selectlist with selected value in view

    - by Rob
    I'm working on a MVC3 web application. I want a list of categories shown when editing a blo from whe applications managements system. In my viewmodel i've got the following property defined for a list of selectlistitems for categories. /// <summary> /// The List of categories /// </summary> [Display(Name = "Categorie")] public IEnumerable<SelectListItem> Categories { get; set; } The next step, my controller contains the following edit action where the list of selectlistitems is filled from the database. public ActionResult Edit(Guid id) { var blogToEdit = _blogService.First(x => x.Id.Equals(id)); var listOfCategories = _categorieService.GetAll(); var selectList = listOfCategories.Select(x =>new SelectListItem{Text = x.Name, Value = x.Id.ToString(), Selected = x.Id.Equals(blogToEdit.Category.Id)}).ToList(); selectList.Insert(0, new SelectListItem{Text = Messages.SelectAnItem, Value = Messages.SelectAnItem}); var viewModel = new BlogModel { BlogId = blogToEdit.Id, Active = blogToEdit.Actief, Content = blogToEdit.Text, Title = blogToEdit.Titel, Categories = selectList //at this point i see the expected item being selected //Categories = new IEnumerable<SelectListItem>(listOfCategories, "Id", "Naam", blogToEdit.CategorieId) }; return View(viewModel); } When i set a breakpoint just before the view is being returned, i see that the selectlist is filled as i expected. So at this point everything seems to be okay. The viewmodel is filled entirely correct. Then in my view (i'm using Razor) i've got the following two rules which are supposed to render the selectlist for me. @Html.LabelFor(m => m.Categories) @Html.DropDownListFor(model=>model.Categories, Model.Categories, Model.CategoryId) @Html.ValidationMessageFor(m => m.Categories) When I run the code and open the view to edit my blog, I can see all the correct data. Also the selectlist is rendered correctly, but the item i want to be selected lost it's selection. How can this be? Until the point the viewmodel is being returned with the view everything is okay. But when i view the webpage in the browser, the selectlist is there only with out the correct selection. What am I missing here? Or doing wrong?

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  • WPF how to fill combobox in data grid

    - by Rizwan Ullah
    public class DA_ActivityType { public int Id { get; set; } public string Name { get; set; } } public static List GetActivitytypes() { DataContext dbo = new DataContext(); IEnumerable activityTypes = from actType in dbo.ActivityTypes select new DA_ActivityType { Id = actType.TypeId, Name = actType.Name }; return activityTypes.ToList(); } //XAML Code

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  • HttpSessionState as parameter

    - by HeavyWave
    What is the highest class in the hierarchy I can use to pass HttpSessionState as a parameter and add values to it? For instance to a method like public void MyMethod(IDictionary<string, object> input) { input.Add("something", something); } I see that implements ICollection and IEnumerable, but that only allows me to read values, not add them.

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