EzDevInfo.com

"Items collection must be empty before using ItemsSource."

I'm trying to get images to display in a WPF ListView styled like a WrapPanel as described in this old ATC Avalon Team article: How to Create a Custom View.

When I try to populate the ListView with a LINQ-to-Entities queried collection of ADO.NET Entity Framework objects I get the following exception:

Exception

Items collection must be empty before using ItemsSource.

My code…

Visual Basic

Private Sub Window1_Loaded(...) Handles MyBase.Loaded
    ListViewImages.ItemsSource = From g In db.Graphic _
                                 Order By g.DateAdded Ascending _
                                 Select g
End Sub

XAML

<ListView Name="ListViewImages"
          SelectionMode="Single"
          ItemsSource="{Binding}">
    <local:ImageView />
</ListView>

I put a breakpoint on that line. ListViewImages.ItemsSource is Nothing just before the LINQ assignment.

How to enable assembly bind failure logging (Fusion) in .NET

How do I enable assembly bind failure logging (Fusion) in .NET?

How to get evaluated attributes inside a custom directive

I'm trying to get an evaluated attribute from my custom directive, but I can't find the right way of doing it.

I've created this jsFiddle to elaborate.

<div ng-controller="MyCtrl">
    <input my-directive value="123">
    <input my-directive value="{{1+1}}">
</div>

myApp.directive('myDirective', function () {
    return function (scope, element, attr) {
        element.val("value = "+attr.value);
    }
});

What am I missing?

Set value to null in WPF binding

please take a look at the following line

<TextBox Text="{Binding Price}"/>

This Price property from above is a Decimal? (Nullable decimal).

I want that if user deletes the content of the textbox (i.e. enters empty string, it should automatcally update source with null (Nothing in VB).

Any ideas on how I can do it 'Xamly'?

A TwoWay or OneWayToSource binding cannot work on the read-only property

I've a read only property I need to display in a textbox, and getting this error at runtime. I've set IsEnabled="False", IsReadOnly="True" - no luck. Other searches say the readonly should fix it, but not for me. I've got an ugly workaround by adding a dummy setter...

How do I invert BooleanToVisibilityConverter?

I'm using a BooleanToVisibilityConverter in WPF to bind the Visibility property of a control to a Boolean. This works fine, but I'd like one of the controls to hide if the boolean is true, and show if it's false.

How to bind multiple values to a single WPF TextBlock?

I'm currently using the TextBlock below to bind the value of a property named Name:

<TextBlock Text="{Binding Name}" />

Now, I want to bind another property named ID to the same TextBlock.

Is it possible to bind two or more values to the same TextBlock? Can it be done with simple concatenation, like Name + ID and, if not, how else could this be approached?

Bind jQuery UI autocomplete using .live()

I've searched everywhere, but I can't seem to find any help...

I have some textboxes that are created dynamically via JS, so I need to bind all of their classes to an autocomplete. As a result, I need to use the new .live() option.

As an example, to bind all items with a class of .foo now and future created:

$('.foo').live('click', function(){
  alert('clicked');
});

It takes (and behaves) the same as .bind(). However, I want to bind an autocomplete...

This doesn't work:

$('.foo').live('autocomplete', function(event, ui){
  source: 'url.php' // (surpressed other arguments)
});

How can I use .live() to bind autocomplete?

UPDATE

Figured it out with Framer:

$(function(){
  $('.search').live('keyup.autocomplete', function(){
    $(this).autocomplete({
      source : 'url.php'
    });
  });
});

Angular Template Default Value if Binding Null / Undefined (With Filter)

I have a template binding that displays a model attribute called 'date' which is a date, using Angular's date filter.

<span class="gallery-date">{{gallery.date | date:'mediumDate'}}</span>

So far so good. However at the moment, if there is no value in the date field, the binding displays nothing. However, I would like it to display the string 'Various' if there is no date.

I can get the basic logic using a binary operator:

<span class="gallery-date">{{gallery.date || 'Various'}}</span>

However I can't get it to work with the date filter:

<span class="gallery-date">{{gallery.date | date:'mediumDate' || "Various"}}</span>

How can I use the binary operator alongside the date filter?

Passing two command parameters using a WPF binding

I have a command which I am executing from my XAML file using the following standard syntax:

<Button Content="Zoom" Command="{Binding MyViewModel.ZoomCommand}"/>

This worked fine until I realized that I needed TWO pieces of information from the view in order to make this operation complete the way users expect (the width and height of the canvas specfically).

It seems like it's possible to pass an array as an argument to my command, but I don't see there being a way to specify the binding to my two canvas properties in the CommandParameter:

<Button Content="Zoom" 
        Command="{Binding MyViewModel.ZoomCommand" 
        CommandParameter={Binding ElementName=MyCanvas, Path=Width}"/>

How do I pass both Width and Height to my command? It doesn't seem like this is possible using commands from XAML and I need to wire up a click handler in my codebehind to get this information to pass to my zoom method.

DataTrigger where value is NOT null?

I know that I can make a setter that checks to see if a value is NULL and do something. Example:

<TextBlock>
  <TextBlock.Style>
    <Style>
      <Style.Triggers>
        <DataTrigger Binding="{Binding SomeField}" Value="{x:Null}">
          <Setter Property="TextBlock.Text" Value="It's NULL Baby!" />
        </DataTrigger>
      </Style.Triggers>
    </Style>
  </TextBlock.Style>
</TextBlock>

But how can I check for a "not" value... as in "NOT NULL", or "NOT = 3"? Is that possible in XAML?

Results: Thanks for your answers... I knew I could do a value converter (which means I would have to go in code, and that would not be pure XAML as I hoped for). However, that does answer the question that effectively "no" you can't do it in pure XAML. The answer selected, however, shows probably the best way to create that kind of functionality. Good find.

How to bind a List to a DataGridView control?

I have a simple List<string> and I'd like it to be displayed in a DataGridView column.
If the list would contain more complex objects, simply would establish the list as the value of its DataSource property.

But when doing this:

myDataGridView.DataSource = myStringList;

I get a column called Length and the strings' lengths are displayed.

How to display the actual string values from the list in a column?

WPF binding with StringFormat doesn't work on ToolTips

The following code has a simple binding which binds the Text of the TextBlock named MyTextBlock to TextBox's Text and ToolTip property using the exact same Binding notation:

<StackPanel>
    <TextBlock x:Name="MyTextBlock">Foo Bar</TextBlock>
    <TextBox    Text="{Binding ElementName=MyTextBlock, Path=Text, StringFormat='It is: \{0\}'}"
             ToolTip="{Binding ElementName=MyTextBlock, Path=Text, StringFormat='It is: \{0\}'}" />
</StackPanel>

The binding also uses the StringFormat property introduced with .NET 3.5 SP1 which is working fine for the above Text property but seems to be broken for the ToolTip. The expected result is "It is: Foo Bar" but when you hover over the TextBox, the ToolTip shows only the binding value, not the string formatted value. Any ideas?

Let vs. Binding in Clojure

I understand that they're different since one works for setting *compile-path* and one doesn't. However, I need help with why they're different.

let creates a new scope with the given bindings, but binding...?

Python list comprehension rebind names even after scope of comprehension. Is this right?

List comprehensions are having some unexpected interactions with scoping. Is this the expected behaviour?

I've got a method:

def leave_room(self, uid):
  u = self.user_by_id(uid)
  r = self.rooms[u.rid]

  other_uids = [ouid for ouid in r.users_by_id.keys() if ouid != u.uid]
  other_us = [self.user_by_id(uid) for uid in other_uids]

  r.remove_user(uid) # OOPS! uid has been re-bound by the list comprehension above

  # Interestingly, it's rebound to the last uid in the list, so the error only shows
  # up when len > 1

At the risk of whining, this is a brutal source of errors. As I write new code, I just occasionally find very weird errors due to rebinding -- even now that I know it's a problem. I need to make a rule like "always preface temp vars in list comprehensions with underscore", but even that's not fool-proof.

The fact that there's this random time-bomb waiting kind of negates all the nice "ease of use" of list comprehensions.