Re: Trying To Shutdown WPF App - Application.Current is null - WPF Discussion Boards

Trying To Shutdown WPF App - Application.Current is null

2-Nov-11 18:04

You can loop over the set of grids in your xaml, get the appropriate control (access the children and get the column name) and then set its MinWidth value to what you need. This is not the neatest way to do this, but will get the width set.

Kevin Marois2-Nov-11 6:55

Kevin Marois

2-Nov-11 6:55

Here's the code

private void login()
{
    Login loginView = new Login();
    loginView.ShowDialog();

    if (MyAppEngine.CurrentUser == null)
    {
        Application.Current.Shutdown();
    }
}

The app is crashing with a null object ref exception on the Shutdown line when I fail to log in. Why would Application.Current ever be null??

Everything makes sense in someone's mind

Re: Trying To Shutdown WPF App - Application.Current is null

SledgeHammer012-Nov-11 7:49

SledgeHammer01

2-Nov-11 7:49

Probably calling this method too early??

Re: Trying To Shutdown WPF App - Application.Current is null

Kevin Marois2-Nov-11 8:38

Kevin Marois

2-Nov-11 8:38

But during runtime you would thnk that Application.Current would exist.

Everything makes sense in someone's mind

Re: Trying To Shutdown WPF App - Application.Current is null

SledgeHammer012-Nov-11 8:47

SledgeHammer01

2-Nov-11 8:47

As I said, depends from where. If you are calling your method really early on (say in the app constructor, or a main() override, the start up code that inits that property hasn't executed yet.

Re: Trying To Shutdown WPF App - Application.Current is null

Pete O'Hanlon2-Nov-11 8:52

Pete O'Hanlon

2-Nov-11 8:52

I assume that you are running this prior to the initialisation of the application pump. If you take control of starting your application (i.e. you don't just rely on StartupUri), you need to be aware of when your application actually "starts". I'd say that your logic would be better expressed as:

if (login())
{
  // Startup the app and show the main window.
}
// If you get here without the "pump" taking over then you just fall out of your app gracefully.

Forgive your enemies - it messes with their heads

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

My blog | My articles | MoXAML PowerToys | Mole 2010 - debugging made easier - my favourite utility

Is there an existing Color-picker in WPF/Silverlight ?

Loveisasea2-Nov-11 5:22

Loveisasea

2-Nov-11 5:22

as captioned.

Is there an existing control to pick a color just like the datepicker ? I can not find it in the MSDN library ....

Re: Is there an existing Color-picker in WPF/Silverlight ?

Mark Salsbery2-Nov-11 5:25

Re: Is there an existing Color-picker in WPF/Silverlight ?

2-Nov-11 5:25

No but there's lots of example source code floating around...

Mark Salsbery
Java | [Coffee]

Pete O'Hanlon2-Nov-11 5:28

Pete O'Hanlon

2-Nov-11 5:28

Our very own Sacha Barber has implemented just such a thing[^]. Enjoy.

Forgive your enemies - it messes with their heads

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

My blog | My articles | MoXAML PowerToys | Mole 2010 - debugging made easier - my favourite utility

Re: Is there an existing Color-picker in WPF/Silverlight ?

Abhinav S2-Nov-11 18:13

Items collection must be empty before using ItemsSource.

2-Nov-11 18:13

VectorLight has a color picker[^] that you could use.

jhoga2-Nov-11 4:39

jhoga

2-Nov-11 4:39

I keep getting this error. I kind of new to wpf and not sure what the issue is.
Here is my code:

XML

<DataGrid AutoGenerateColumns="False" Height="770" Name="DataGrid1" Width="1506" ItemsSource="{Binding}">
        <Style TargetType="{x:Type DataGridRow}" >
            <Style.Triggers>
                <DataTrigger Binding="{Binding Alert_Level}" Value="1">
                    <Setter Property="Background" Value="LightYellow" />
                </DataTrigger>
            </Style.Triggers>
        </Style>

<DataGrid.Columns>

XML

<DataGridTextColumn Header="ID" Binding="{Binding TicketID}" IsReadOnly="True" Width="70" FontSize="24" />
            <DataGridTextColumn Header="Date" Binding="{Binding Date_Entered}" IsReadOnly="True" Width="100" FontSize="24" />
            <DataGridTextColumn Header="Input By" Binding="{Binding Requestor}" IsReadOnly="True" Width="200" FontSize="24"/>
            <DataGridTextColumn Header="Telephone" Binding="{Binding Requestor_telep}" IsReadOnly="True" Width="120" FontSize="24"/>
            <DataGridTextColumn Header="Status" Binding="{Binding Status}" IsReadOnly="True" Width="120" FontSize="24"/>
            <DataGridTextColumn Header="Alert" Binding="{Binding Alert_Level}" IsReadOnly="True" Width="40" FontSize="24"/>
            <DataGridTextColumn Header="Assigned" Binding="{Binding Assigned_To}" IsReadOnly="True" Width="200" FontSize="24"/>
            <DataGridTextColumn Header="Issue" Binding="{Binding Problem_detail}" IsReadOnly="True" Width="300*" FontSize="24"/>
        </DataGrid.Columns>

</DataGrid>

Thanks

Re: Items collection must be empty before using ItemsSource.

Mark Salsbery2-Nov-11 5:23

Re: Items collection must be empty before using ItemsSource.

2-Nov-11 5:23

I would guess based on what you've shown, the Style ends up being just a datagrid item (an object representing a datagrid row). That style should be in the resources somewhere, for example

<DataGrid ...>
    <DataGrid.Resources>
        <Style TargetType="{x:Type DataGridRow}" >
            <Style.Triggers>
                <DataTrigger Binding="{Binding Alert_Level}" Value="1">
                    <Setter Property="Background" Value="LightYellow" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </DataGrid.Resources>
    <DataGrid.Columns>
     ...
    </DataGrid.Columns>
<DataGrid>

Mark Salsbery
Java | [Coffee]

jhoga2-Nov-11 5:52

jhoga

2-Nov-11 5:52

Thanks mark,
That took care of my error. I still can not get the background to show a color base on a value. But that is a complete separate issue. Thanks for your help Wink | ;)

Re: Items collection must be empty before using ItemsSource.

Mark Salsbery2-Nov-11 7:06

Re: Items collection must be empty before using ItemsSource.

2-Nov-11 7:06

jhoga wrote:
I still can not get the background to show a color base on a value.

Maybe the resource needs to be at least one level up the tree from the datagrid.

Regardless, perhaps try using ItemContainerStyle instead, something like this

HTML

<DataGrid ...>
    <DataGrid.ItemContainerStyle>
        <Style TargetType="{x:Type DataGridRow}" BasedOn="{StaticResource {x:Type DataGridRow}}" >
            <Style.Triggers>
                <DataTrigger Binding="{Binding Alert_Level}" Value="1">
                    <Setter Property="Background" Value="LightYellow" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </DataGrid.ItemContainerStyle>
    <DataGrid.Columns>
     ...
    </DataGrid.Columns>
<DataGrid>

Mark Salsbery
Java | [Coffee]

jhoga2-Nov-11 8:57

jhoga

2-Nov-11 8:57

Thanks Mark,
I tried that with no luck. I found the issue the value of Alert_Level was not numeric. Once I changed it to an int everything worked fine. Thanks for your help. Smile | :)

How to make listbox list items in horizontal

Loveisasea1-Nov-11 19:47

Loveisasea

1-Nov-11 19:47

By default listbox list items in vertical. Now I want to list them in horizontal. I remember this can only be set in ListBox's Style. But I forget the full name of the Property and can not find it out in the past 2 hours. Cry | :((

Anyone know this property name?

Abhinav S1-Nov-11 19:56

1-Nov-11 19:56

Put the ItemsPresenter inside a Stackpanel with horizontal orientation.

Mycroft Holmes1-Nov-11 21:03

Mycroft Holmes

1-Nov-11 21:03

Is that better (or different) to using a contentpresenter, and I used a wrappanel as there were quite a few images.

Never underestimate the power of human stupidity
RAH

Abhinav S1-Nov-11 21:51

1-Nov-11 21:51

If a VirtualizingStackPanel has been used, I suppose there might be a performance benefit in terms of loading a large amount of data together (inside an ItemsControl). A ListBox uses this panel by default.

Otherwise I'm not aware of any differences.

Loveisasea1-Nov-11 22:14

Loveisasea

1-Nov-11 22:14

Thanks guys.

My design intention is listbox inside listbox. The items of the outer listbox binds with days. so it is better let days shown horizontal. Items of inner listbox binds with things to do in specific day. So If only a property setting can achieve it, it will save time and maintainace effort.

Mark Salsbery2-Nov-11 5:38

2-Nov-11 5:38

Maybe this?

XML

<ListBox >
    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
            <VirtualizingStackPanel Orientation="Horizontal" IsItemsHost="True" />
        </ItemsPanelTemplate>
    </ListBox.ItemsPanel>
</ListBox>

Mark Salsbery
Java | [Coffee]