Databases
StackOverflow2013
Postsdbo
POOpening a new dialog using WPF with MVVM
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POOpening a new dialog using WPF with MVVM
    primarykey
    data
    text
    <p>I am currently using MVVM (Light) to build an application with WPF. However, in a few cases I must open a new dialog (also WPF) when the user clicks a button. However, this is being a tough fight.</p> <p>Here is how I am doing it:</p> <pre><code> private void _ShowItemDialog(Item item) { var itemVM = new ItemViewModel(); itemVM.CurrentItem = item ?? new Item(); itemVM.Load(); var itemView = new View.ItemView() { DataContext = itemVM }; if (itemView.ShowDialog() == true) { if (item == null) { itemList.Add(itemVM.CurrentItem); } } itemVM.Cleanup(); } </code></pre> <p>And the itemView XAML there is no binding to the DataContext, otherwise two different instances of the ViewModel would be created.</p> <p>Inside the Window tag. To have the result at ShowDialog, I use the DialogCloser code:</p> <pre><code> public static class DialogCloser { public static readonly DependencyProperty DialogResultProperty = DependencyProperty.RegisterAttached( "DialogResult", typeof(bool?), typeof(DialogCloser), new PropertyMetadata(DialogResultChanged)); private static void DialogResultChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { var window = d as Window; if (window != null) window.DialogResult = e.NewValue as bool?; } public static void SetDialogResult(Window target, bool? value) { target.SetValue(DialogResultProperty, value); } } </code></pre> <p>In the ItemView, this is declared inside Window tag as follows:</p> <pre><code>my:DialogCloser.DialogResult="{Binding DialogResult}" </code></pre> <p>And when the dialog is closed, the closing event sets DialogResult to true or false.</p> <p>This works perfectly for the first time the screen is opened, but it is not possible to open the dialog again after it is closed.</p> <p>I would like to know if you have any better ideas for opening the dialog, and why this code does not work.</p> <p>Thanks!</p> <p><strong>EDIT:</strong> I have already fixed the code. What I need to do is create a new ViewModel and attach it to the DataContext every time the dialog is opened. Moreover, I had to remove the DataContext binding from XAML. Please check the code changes above.</p> <p>With these changes I have found out that it is not possible to use the ViewModel from ViewModelLocator because it is a "singleton" and not a new instance at each new window. Therefore, the DialogResult held the last value and if I tried to change its value back to null (as it is when the ViewModel is initialized) an exception is thrown. Do you have any clues of why this happens? It would be very good for me to use the ViewModel from ViewModelLocator, since it would keep the same strategy throughout the system.</p> <p>Thank you!</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USjpnavarini
    1. USjpnavarini
    plurals
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POOpening a new dialog using WPF with MVVM
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI am not sure if I get you right. To create a new ViewModel instance for your View, every time your View is generated, you can create an instance of your ViewModel in the Views code behind and set the Views DataContext to that new generated ViewModel.
      singulars
      1. POOpening a new dialog using WPF with MVVM
      1. USAndre
    2. CO@Andre I would not like to create a new ViewModel for each View. It is exactly the oposite. I would like to use the ViewModel singleton, however I don't understand why using the same instance for new windows opened does not work. Moreover, why can't I "erase" the DialogResult?
      singulars
      1. POOpening a new dialog using WPF with MVVM
      1. USjpnavarini
 

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