Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>EDIT: Overhauling this answer to be more specific to the question since the tags show you already knew about <a href="http://msdn.microsoft.com/en-us/library/ms743695.aspx" rel="noreferrer"><code>INotifyPropertyChanged</code></a>.</p> <p>You need to implement <code>INotifyPropertyChanged</code> in class <code>A</code> and in class <code>S</code>. Make it so <code>objectA</code> can only be set through a property that will raise the <code>PropertyChanged</code> event on S whenever a property is changed in <code>A</code>. Example:</p> <pre><code>public class A : INotifyPropertyChanged { private string name; public string Name { get { return name; } set { name = value; OnPropertyChanged("Name"); } } private int count; public int Count { get { return count; } set { count = value; OnPropertyChanged("Count"); } } public event PropertyChangedEventHandler PropertyChanged; protected void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } </code></pre> <p>... and class <code>S</code>...</p> <pre><code>public class S : INotifyPropertyChanged { private string name, ID; private A objectA; public A ObjectA { get { return objectA; } set { var old = objectA; objectA = value; // Remove the event subscription from the old instance. if (old != null) old.PropertyChanged -= objectA_PropertyChanged; // Add the event subscription to the new instance. if (objectA != null) objectA.PropertyChanged += objectA_PropertyChanged; OnPropertyChanged("ObjectA"); } } void objectA_PropertyChanged(object sender, PropertyChangedEventArgs e) { // Propagate the change to any listeners. Prefix with ObjectA so listeners can tell the difference. OnPropertyChanged("ObjectA." + e.PropertyName); } public event PropertyChangedEventHandler PropertyChanged; protected void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } </code></pre> <p>For class <code>R</code>, use <code>ObservableCollection&lt;S&gt;</code> instead of <code>List&lt;S&gt;</code>, and subscribe to its <code>CollectionChanged</code> event, and monitor when objects are added or removed to <code>listOfObjectS</code>. When they are added, subscribe to <code>S</code>'s <code>PropertyChanged</code> events. Then updated <code>R</code>'s view. Example:</p> <pre><code>public class R { protected string name; protected System.Collections.ObjectModel.ObservableCollection&lt;S&gt; ListOfObjectS { get; private set; } public R() { // Use ObservableCollection instead. ListOfObjectS = new ObservableCollection&lt;S&gt;(); // Subscribe to all changes to the collection. ListOfObjectS.CollectionChanged += listOfObjectS_CollectionChanged; } void listOfObjectS_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) { if (e.Action == NotifyCollectionChangedAction.Remove) { // When items are removed, unsubscribe from property change notifications. var oldItems = (e.OldItems ?? new INotifyPropertyChanged[0]).OfType&lt;INotifyPropertyChanged&gt;(); foreach (var item in oldItems) item.PropertyChanged -= item_PropertyChanged; } // When item(s) are added, subscribe to property notifications. if (e.Action == NotifyCollectionChangedAction.Add) { var newItems = (e.NewItems ?? new INotifyPropertyChanged[0]).OfType&lt;INotifyPropertyChanged&gt;(); foreach (var item in newItems) item.PropertyChanged += item_PropertyChanged; } // NOTE: I'm not handling NotifyCollectionChangedAction.Reset. // You'll want to look into when this event is raised and handle it // in a special fashion. } void item_PropertyChanged(object sender, PropertyChangedEventArgs e) { if (e.PropertyName.StartsWith("ObjectA.")) { // Refresh any dependent views, forms, controls, whatever... } } } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POHow to propagate property change notifications of objects within collections
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USDavid Schwartz
    1. USDavid Schwartz
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POHow to propagate property change notifications of objects within collections
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COOne nit, not all calls to a setter need to trigger a `OnPropertyChanged`, normally you will want to do a `Object.Equals(backingMember, value)` check (and because you did not override `Equals(object)` it will be a reference equality check, which is fine in this situation) to see if the property really was changed before notifying any subscribers of that fact.
      singulars
      1. PO
      1. USScott Chamberlain
    2. CO@Scott Agreed, esp. because redrawing the UI is so slow. I am probably not going to update the example code, however, because it's pretty verbose already and every added line makes it more difficult to digest. In some situations, it may be desirable that setting the property (even if the value didn't change) cause a refresh. Not exactly how it was meant to be used, but I've seen it before. As a nit of my own, I would not use `Object.Equals` because we know the type, so `EqualityComparer<T>.Default.Equals(backingValue, value)` would be a better choice.
      singulars
      1. PO
      1. USDavid Schwartz
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload