listt - Developer IT

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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Generic List<T> as IEnumerable<object>

- by Avi

I'm trying to do cast a List to an IEnumerable, so I can verify that different lists are not null or empty: Suppose myList is a List < T . Then in the caller code I wanted: Validator.VerifyNotNullOrEmpty(myList as IEnumerable<object>, @"myList", @"ClassName.MethodName"); The valdiating code would be: public static void VerifyNotNullOrEmpty(IEnumerable<object> theIEnumerable, string theIEnumerableName, string theVerifyingPosition) { string errMsg = theVerifyingPosition + " " + theIEnumerableName; if (theIEnumerable == null) { errMsg += @" is null"; Debug.Assert(false); throw new ApplicationException(errMsg); } else if (theIEnumerable.Count() == 0) { errMsg += @" is empty"; Debug.Assert(false); throw new ApplicationException(errMsg); } } However, this doens't work. It compiles, but theIEnumerable is null! Why?

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C# XMLSerializer fails with List<T>

- by Redshirt

Help... I'm using a singleton class to save all my settings info. It's first utilized by calling Settings.ValidateSettings(@"C:\MyApp") The problem I'm having is that 'List Contacts' is causing the xmlserializer to fail to write the settings file, or to load said settings. If I comment out the List then I have no problems saving/loading the xml file. What am I doing wrong... Thanks in advance // The actual settings to save public class MyAppSettings { public bool FirstLoad { get; set; } public string VehicleFolderName { get; set; } public string ContactFolderName { get; set; } public List<ContactInfo> Contacts { get { if (contacts == null) contacts = new List<ContactInfo>(); return contacts; } set { contacts = value; } } private List<ContactInfo> contacts; } // The class in which the settings are manipulated public static class Settings { public static string SettingPath; private static MyAppSettings instance; public static MyAppSettings Instance { get { if (instance == null) instance = new MyAppSettings(); return instance; } set { instance = value; } } public static void InitializeSettings(string path) { SettingPath = Path.GetFullPath(path + "\\MyApp.xml"); if (File.Exists(SettingPath)) { LoadSettings(); } else { Instance.FirstLoad = true; Instance.VehicleFolderName = "Cars"; Instance.ContactFolderName = "Contacts"; SaveSettingsFile(); } } // load the settings from the xml file private static void LoadSettings() { XmlSerializer ser = new XmlSerializer(typeof(MyAppSettings)); TextReader reader = new StreamReader(SettingPath); Instance = (MyAppSettings)ser.Deserialize(reader); reader.Close(); } // Save the settings to the xml file public static void SaveSettingsFile() { XmlSerializer ser = new XmlSerializer(typeof(MyAppSettings)); TextWriter writer = new StreamWriter(SettingPath); ser.Serialize(writer, Settings.Instance); writer.Close(); } public static bool ValidateSettings(string initialFolder) { try { Settings.InitializeSettings(initialFolder); } catch (Exception e) { return false; } // Do some validation logic here return true; } } // A utility class to contain each contact detail public class ContactInfo { public string ContactID; public string Name; public string PhoneNumber; public string Details; public bool Active; public int SortOrder; } }

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Decorator Pattern on List<T> for DataGridView

- by elector

Hi all, I would like to apply a Decorator on List class and be able to bind it to the WinForms DataGirdView. I would like to know what members of List i need to implement for this new class to be able to bind it to DataGrid. Some of the methods from List I would hide with my decorated class methods and others I would just call _decoratedList.Method(). Is this an option for implementing Decorator on List type? Decorator: public class MyCustomList : List<MyObject> { List<MyObject> _decoratedList; . . . }

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hackage package dependencies and future-proof libraries

- by yairchu

In the dependencies section of a cabal file: Build-Depends: base >= 3 && < 5, transformers >= 0.2.0 Should I be doing something like Build-Depends: base >= 3 && < 5, transformers >= 0.2.0 && < 0.3.0 (putting upper limits on versions of packages I depend on) or not? I'll use a real example: my "List" package on Hackage (List monad transformer and class) If I don't put the limit - my package could break by a change in "transformers" If I do put the limit - a user that uses "transformers" but is using a newer version of it will not be able to use lift and liftIO with ListT because it's only an instance of these classes of transformers-0.2.x I guess that applications should always put upper limits so that they never break, so this question is only about libraries: Shall I use the upper version limit on dependencies or not?

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