WPF Discussion Boards

Re: ActualWidth value is becoming 0

7-Nov-11 6:52

I think everything is working "as expected" Smile | :)

. You just expected the wrong outcome Smile | :)

. I suspect the layout cycle is resulting in your TextBlock wrapping to a width of 0.

I'd get rid of the column definition, get rid of MaxWidth on StackPanel and add something like this to TextBlock:

Width={Binding ElementName=grid, Path=ActualWidth}

That way you are sizing the TextBlock to the width of the grid and it'll wrap to that width.

indian1438-Nov-11 14:57

indian143

8-Nov-11 14:57

Hi,

No use, its not working still. Why MS has created this binding IDK but that never ever works for me at all.

Why did MS has created this complex I dont know.

Thanks & Regards,

Abdul Aleem Mohammad
St Louis MO - USA

Keep messagebox on top of window [Solved]

WelshChris4-Nov-11 4:07

4-Nov-11 4:07

I have an application which, while displaying a splash screen, checks for the presence of several files required for the proper running of the main window. If a file is not found the filename is passed to a method and the following should happen:

> progressbar colour changed to indicate an error
> status message(normally used to tell the user what the app is doing) tells the user that something has gone wrong
> a messagebox is displayed, giving the user the exact name of the required file that is missing.

The problem I'm having is that if a file is found to be missing, the messagebox displays but the splash never does. Is there a way to do it so that the messagebox appears over the top of the window ?

modified 4-Nov-11 13:47pm.

Wayne Gaylard4-Nov-11 4:14

Wayne Gaylard

4-Nov-11 4:14

I think what is happening is that everything is running on the UI thread, and so locking up the splash screen. You should try running the file search on a separate thread(BackgroundWorker) or in a new task if you are using .Net 4.0.

When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman

WelshChris4-Nov-11 4:21

4-Nov-11 4:21

Hmm haven't used either options before, guess I've got some googling to do. Laugh | :laugh:

Wayne Gaylard4-Nov-11 4:29

Wayne Gaylard

4-Nov-11 4:29

Sacha Barber wrote an excellent series of articles on the Task Parallel Library . Here[^] is the first one to start you off. Have fun! Smile | :)

When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman

WelshChris4-Nov-11 6:54

4-Nov-11 6:54

I've got my task set up, now to stop it complaining that the progressbar is owned by another thread :/

*Edit* Looks like I'm going to half to split my foreach which goes through a string array and checks each required file into seperate tasks for each one. All this effort for something that should be so simple Cry | :((

modified 4-Nov-11 13:15pm.

SledgeHammer014-Nov-11 7:15

4-Nov-11 7:15

All UI objects are owned by the UI thread. You can't access them from another thread. This is by design. You need to use the thread dispatcher. Something like:

Dispatcher.Invoke(DispatcherPriority.Input, new Action(() =>
{
// do stuff in here
}));

WelshChris4-Nov-11 7:29

4-Nov-11 7:29

Thanks, got it sorted. Now to figure out why the whole app dies if fluent.dll (from http://fluent.codeplex.com) isn't there when only the main window needs it and isn't run until the splash screen tells it to.

*Edit* Was setting default theme in app.xaml, moved that and everthings fine. Thanks guys ! Thumbs Up | :thumbsup:

modified 4-Nov-11 13:46pm.

WPF Editable ComboBox In GridView

Wayne Gaylard4-Nov-11 8:11

Wayne Gaylard

4-Nov-11 8:11

Glad you got it sorted. Thumbs Up | :thumbsup:

When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman

WPF

Unque4-Nov-11 3:06

Unque

4-Nov-11 3:06

Please can anyone explain

XML

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
  
  <Grid>

what is this xmlns:x? why it use?

Re: WPF

Abhinav S4-Nov-11 3:15

Abhinav S

4-Nov-11 3:15

"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

The relationship between these declarations is that the x: prefix mapping supports the intrinsics that are part of the XAML language definition, and WPF is one implementation that uses XAML as a language and defines a vocabulary of its objects for XAML. Because the WPF vocabulary's usages will be far more common than the XAML intrinsics usages, the WPF vocabulary is mapped as the default.
The x: prefix convention for mapping the XAML language intrinsics support is followed by project templates, sample code, and the documentation of language features within this SDK."

I have posted this from here[^].

Kevin Marois3-Nov-11 13:18

3-Nov-11 13:18

I cannot seem to find what I'm looking for....

I need to provide a grid with 2 columns: Item and Quantity.

In the Item column I want to have an editable combobox so that the user can pick an item from the list or type something in. The value they type in does not have to be the combo's data collection.

I'm not sure how to do this so I don't know what to search for. Anyone done this? Got an example?

Many thanks

Everything makes sense in someone's mind

SledgeHammer013-Nov-11 16:13

3-Nov-11 16:13

Sounds like you want a PropertyGrid to me. Thats exactly what it does.

Kevin Marois4-Nov-11 7:57

4-Nov-11 7:57

Ok, I've been working with this for a while and I'm not gtting it. This post is a bit long but explains things better than my first post.

I have a Query view in my app. The user can type in any search terms they want. In this screenshot I entered Item1 - Item5.
www.maroisconsulting.com/image/Query1.png[^]

When the user clicks the Apply button, what I want to happen is to hide the textbox and show the grid. Both are on the view. The textbox is initially visible and the grid is initially hidden.

The Apply method converts the search terms into a list of objects:

private void apply()
{
    // The property 'SearchTerms' is bound to the textbox. This converts the text into an array
    string[] temp = SearchTerms.Split(new string[] { Environment.NewLine }, StringSplitOptions.None);

    // Convert the array into a list
    var temp2 = (from s in temp
                    where s != string.Empty
                    select new SearchItemModel
                    {
                        SearchTerm = s,
                        Quantity = 1
                    }).ToList();

    // Store the list to the SearchItems property. This property is bound to the grid's ItemSource
    SearchItems = new ObservableCollection<SearchItemModel>(temp2);
                
    // Togggle the textbox & grid visibility
    GridVisible = true;
    TextAreaVisible = false;
}

There are 2 columns on the grid. The first column is an editable combobox. It's source of data is a list of project names stored in a collection called 'BOMs' (Bills of Materials), something like

Project A4472A
BOM Project B2215B
Some Other BOM

The user should then be able to either type in any text to search on, or select a BOM project name from the combox box.

Here's the relevant XAML:

<DataGrid x:Name="grdItems"
            Grid.Row="4"
            Grid.Column="0"
            Grid.ColumnSpan="2"
            AutoGenerateColumns="False"
            ItemsSource="{Binding SearchItems}"
            Visibility="{Binding GridVisible, Converter={StaticResource visibilityConverter}}"
            Margin="5">

    <DataGrid.Columns>
        <DataGridTemplateColumn Header="Search Terms"
                                Width="*">
            <DataGridTemplateColumn.CellEditingTemplate>
                <DataTemplate>
                    <ComboBox Height="22" 
                                IsEditable="True"
                                ItemsSource="{Binding BOMs}"
                                SelectedItem="{Binding SelectedBOMItem}"></ComboBox>
                </DataTemplate>
            </DataGridTemplateColumn.CellEditingTemplate>
        </DataGridTemplateColumn>
        <DataGridTextColumn Header="Quantity" 
                            Binding="{Binding Quantity}"
                            Width="100">
        </DataGridTextColumn>
    </DataGrid.Columns>

</DataGrid>

After the Apply method runs, I get this: http://www.maroisconsulting.com/image/Query2.png[^]

What I would like to get is this (mocked up):
http://www.maroisconsulting.com/image/Query3.png[^]

Hope this made sense. Any thoughts on how to do this?

[UPDATE]
The Output window shows 2 errors:
"BindingExpression path error: 'BOMs' property not found on 'object' ''SearchItemModel' ("
"BindingExpression path error: 'SelectedBOMItem' property not found on 'object' ''SearchItemModel'"

Everything makes sense in someone's mind

SledgeHammer014-Nov-11 8:14

4-Nov-11 8:14

Ah... ignore my suggestion of a property grid then since that'll only let you edit the right hand side.

Are the 'BOMs' and 'SelectedBOMItem' properties actually public properties in SearchItemModel? Seems like WPF is resolving to the proper DataContext (which I initially thought was the issue when I saw your XAML).

Are you sure that XAML you posted is EXACTLY the XAML you had when you got those error messages? Because if it is, it doesn't make sense. If BOMs and SelectedBOMItem are public props in SearchItemModel, they should be resolved since WPF seems to be looking at the right DataContext judging by those errors.

Kevin Marois4-Nov-11 8:18

4-Nov-11 8:18

BOMs is a collection on the VM, and SelectedBOMItem is a property on the VM.

What I think is happening is since the grid is bound to a collection of SearchItems models, the combo thinks the BOMs and SelectedBOMItem object are on that model. I'm not sure, but that's what I got out of those messages. And, assuming thats the problem, I'm not sure how to tell the combo to look on the DataContext, not the SearchItems.

Everything makes sense in someone's mind

SledgeHammer014-Nov-11 8:41

4-Nov-11 8:41

Ok, you confused me with your terminology / naming Smile | :)

... the problem is just as I originally suspected. The combobox is looking at the datacontext of the grid, not the VM. You can do something like (assuming your window has a name using the Name="myWindow" tag)...

<ComboBox DataContext={Binding ElementName=myWindow, Path=DataContext} ...

Kevin Marois4-Nov-11 8:49

4-Nov-11 8:49

Ok, I see where you're going. The problem now is, these controls are inside a user control which is inside the main window.

The user control is named QueryView, and its VM is QueryViewModel, so I tried:

<DataGrid x:Name="grdItems"
            Grid.Row="4"
            Grid.Column="0"
            Grid.ColumnSpan="2"
            AutoGenerateColumns="False"
            ItemsSource="{Binding SearchItems}"
            Visibility="{Binding GridVisible, Converter={StaticResource visibilityConverter}}"
            Margin="5">

    <DataGrid.Columns>
        <DataGridTemplateColumn Header="Search Terms"
                                Width="*">
            <DataGridTemplateColumn.CellEditingTemplate>
                <DataTemplate>
                    <ComboBox Height="22" 
                                DataContext="{Binding ElementName=QueryViewModel, Path=DataContext}"
                                IsEditable="True"
                                ItemsSource="{Binding BOMs}"
                                SelectedItem="{Binding SelectedBOMItem}"></ComboBox>
                </DataTemplate>
            </DataGridTemplateColumn.CellEditingTemplate>
        </DataGridTemplateColumn>
        <DataGridTextColumn Header="Quantity" 
                            Binding="{Binding Quantity}"
                            Width="100">
        </DataGridTextColumn>
    </DataGrid.Columns>

</DataGrid>

But I get a binding error in the output window. If I understand what you're trying here, you're telling the combo to get it's data from some other datacontext? The question is, how to tell it about the QueryViewModel that's inside the MainWindowViewModel.

Everything makes sense in someone's mind

SledgeHammer014-Nov-11 8:55

4-Nov-11 8:55

You can't bind to the VM directly. ElementName needs a UIElement... thats why I mentioned that you have to have a Name tag on your top level window Smile | :)

. So its either going to be something like:

<Window Name=myWindow...>

<ComboBox DataContext="{Binding ElementName=QueryViewModel, Path=DataContext}" ... >

or maybe:

<UserControl Name=myWindow...>

Remember, your Window or UserControl DataContext points to your VM. You need to reference that one. I *think* you can also use the DataContext from the DataGrid, so something like:

<ComboBox DataContext="{Binding ElementName=grdItems, Path=DataContext}" ... >

One of those should work Smile | :)

Kevin Marois4-Nov-11 9:01

4-Nov-11 9:01

I dunno. I get what's supposed to happen, I just can't make it work. I'm really starting to think about a different approach.

Everything makes sense in someone's mind

SledgeHammer014-Nov-11 10:34

4-Nov-11 10:34

Should work as long as your are binding to a <b>UIElement</b> that has its DataContext set properly. We already the top level window has its DataContext set to your VM, so you must point your ComboBox's DataContext to the VM if you want to reference properties from the VM.

You might to post your full XAML and what error messages you are getting. Also, try turning on verbose WPF debugging.

Kevin Marois6-Nov-11 7:02

6-Nov-11 7:02

Here's the XAML as it is now:

<DataGrid x:Name="grdItems"
            Grid.Row="4"
            Grid.Column="0"
            Grid.ColumnSpan="2"
            AutoGenerateColumns="False"
            ItemsSource="{Binding SearchItems}"
            Visibility="{Binding GridVisible, Converter={StaticResource visibilityConverter}}"
            Margin="5">

    <DataGrid.Columns>
        <DataGridTemplateColumn Header="Search Terms"
                                Width="*">
            <DataGridTemplateColumn.CellEditingTemplate>
                <DataTemplate>
                    <ComboBox x:Name="cboBOMs"
                                Height="22" 
                                DataContext="{Binding ElementName=QueryView, Path=DataContext}"
                                IsEditable="True"
                                ItemsSource="{Binding BOMs}"
                                SelectedItem="{Binding SelectedBOMItem}"></ComboBox>
                </DataTemplate>
            </DataGridTemplateColumn.CellEditingTemplate>
        </DataGridTemplateColumn>
        <DataGridTextColumn Header="Quantity" 
                            Binding="{Binding Quantity}"
                            Width="100">
        </DataGridTextColumn>
    </DataGrid.Columns>

</DataGrid>

I don't understand what's going on because this code is in QueryView.xaml. You can see the combo is looking for the DC on QueryView.

The output window shows the error:

Cannot find source for binding with reference 'ElementName=QueryView'. BindingExpression:Path=DataContext; DataItem=null; target element is 'ComboBox' (Name='cboBOMs'); target property is 'DataContext' (type 'Object')

This appeaars to be right. I don't get it and I'm tired of screwing with it. if the DB wasn't so damn big I'd post the entire app on my site and ask for more help. I'm fairly frustrated at this point.

Everything makes sense in someone's mind

SledgeHammer017-Nov-11 6:46