Re: WPF Combobox databinding - WPF Discussion Boards

babongita6-Mar-09 5:29

6-Mar-09 5:29

I didn't check the output window to see what was happening. When I hit the dropdown on the combo I couldn't see anything in it, but the itemsource had the values.

But digging into the SelectedIndex seems to be the way to go here, it is performing as expected. But like I said, I will need to get the Index each time the screen loads, since the Index may change, not often but enough that I can't rely on that being the same

I guess I could create a converter for that couldn't I, then it would be more of an "automated" thing, right?

ABitSmart6-Mar-09 5:59

Re: WPF Combobox databinding [modified]

6-Mar-09 5:59

babongita wrote:
I didn't check the output window to see what was happening. When I hit the dropdown on the combo I couldn't see anything in it, but the itemsource had the values.

That is because some binding is failing. If you check the Output window it would clearly mention which binding is failing and why. The comboox SelectedItem is being driven by the SelectedParamter Dependency Property. Check what value it has. If it is null(or the Name property), then the combobox cannot do anything.

babongita wrote:
But digging into the SelectedIndex seems to be the way to go here, it is performing as expected. But like I said, I will need to get the Index each time the screen loads, since the Index may change, not often but enough that I can't rely on that being the same

So, if I understand you correct, you will search for the objects in the comboxbox and set the combobox SelectedIndex to it ? Would this be on the SelectionChange of your listviewm - where you would get the listview's selected item and search that in the combobox ?

babongita wrote:
I could create a converter

Well, that seems to be a *workaround*. I would fix the damn databinding issue Smile | :)

I think you could look at this as an option,

<ComboBox x:Name="cboParameterName"
                           VerticalAlignment="Center"
                           IsSynchronizedWithCurrentItem="True"
                           TabIndex="10"
                           Grid.Column="1"
                           Grid.ColumnSpan="4"
                           ItemsSource="{Binding Path=ParameterNameCollection}"  
                           SelectedItem="{Binding Path=SelectedParameter}" 
                           Style="{DynamicResource BaseComboBox}"
                  <ComboBox.ItemTemplate>
                        <DataTemplate>
                              <TextBlock Text="{Binding Name.ParameterDisplayName}"/>
                        </DataTemplate>
                  </ComboBox.ItemTemplate>
            </ComboBox>

One more thing is, since you are driving this combobox from a listview, why don't you bind the ListView's SelectedItem to the combobox's SelectedItem ,

<ComboBox x:Name="cboParameterName"
                           VerticalAlignment="Center"
                           IsSynchronizedWithCurrentItem="True"
                           TabIndex="10"
                           Grid.Column="1"
                           Grid.ColumnSpan="4"
                           ItemsSource="{Binding Path=ParameterNameCollection}"  
                           SelectedItem="{Binding ElementName="yourListView" Path=SelectedItem}" 
                           Style="{DynamicResource BaseComboBox}"
                  <ComboBox.ItemTemplate>
                        <DataTemplate>
                              <TextBlock Text="{Binding Name.ParameterDisplayName}"/>
                        </DataTemplate>
                  </ComboBox.ItemTemplate>
            </ComboBox>

Have fun

babongita6-Mar-09 6:38

6-Mar-09 6:38

I was thinking about binding to the ListView but the problem I had was that the user has the option to Add/Edit/Remove (all buttons on the view) a parameter, and I couldn't figure out how to add a new parameter and still have it be bound. Does that make sense? Can I email you offline? I would like to discuss this offline with some screen shots of what I am trying to duplicate.

modified on Friday, March 6, 2009 12:46 PM

ABitSmart6-Mar-09 6:41

6-Mar-09 6:41

I do not think it is a good idea to share yur email id in public.

babongita6-Mar-09 6:49

6-Mar-09 6:49

OK well I modified that post. But is it possible that we could continue this offline?

ABitSmart6-Mar-09 6:56

6-Mar-09 6:56

I am a dedicated member, always available at CP Smile | :)

babongita6-Mar-09 7:02

6-Mar-09 7:02

OK I am going back through now and trying you recommendations and this is the error that I am getting in the Output window

System.Windows.Data Error: 39 : BindingExpression path error: 'Name' property not found on 'object' ''ParameterName' (HashCode=62178992)'. BindingExpression:Path=Name.ParameterDisplayName; DataItem='ParameterName' (HashCode=62178992); target element is 'ComboBox' (Name='cboParameterName'); target property is 'NoTarget' (type 'Object')

babongita6-Mar-09 9:03

6-Mar-09 9:03

OK I have finally figured it out, but it really is a different work around. Or at least it seems like it. If instead of creating the ParameterName objects with all of the properties associated with it, if I only create a collection of strings and then bind them to the dropdown box then I can make the binding work. But it is not the object itself it is only one piece of the object.

ABitSmart6-Mar-09 17:47

6-Mar-09 17:47

I am suprised it does not work while binding to the the string property of the object. Well, if it is so, you can use a converter taking the object and returning a string for it rather than having to have a string collection. Which particular binding was failing, the one in the combobox DataTemplate ? I still feel that your data was not being populated correct.

ABitSmart6-Mar-09 3:05

6-Mar-09 3:05

babongita wrote:
but any item bound to an object (in this case a Combobox) that attribute is not populated

The above statement confuses me. It says any item bound to the object is not populated. You mean never or again just when you do something from code ?

babongita6-Mar-09 3:18

6-Mar-09 3:18

OK, There is a listbox below, which is bound to Collection of Parameters(this is a class, not what you would typically think of when you think parameters), then there is a "view" above it which shows the "detail" (attributes) of the SelectedItem in the listbox. All of the TextBoxes or the CheckBoxes show the "detail" (attributes) correctly. But when the "detail" (attribute) is an item in a Combobox the item doesn't show in the Combobox even though it is bound to that "detail"(attribute). The combobox is populated with all of the possible selections, but the SelectedItem, isn't shown in that combobox.

Member 40355135-Mar-09 5:03

Member 4035513

5-Mar-09 5:03

I think that you are missing the ElementName in the ItemsSource Binding. In this case the ElementName is the x:Name of your window or UserControl.

<combobox x:name="cboParameterName" xmlns:x="#unknown">
IsSynchronizedWithCurrentItem="True"
TabIndex="10"
Grid.Column="1"
Grid.ColumnSpan="4"
ItemsSource="{Binding Path=ParameterNameCollection, ElementName=UserControl, Mode=Default}"
SelectedValue="{Binding SelectedParameter.Name}"
Style="{DynamicResource BaseComboBox}">
<combobox.itemtemplate>
<datatemplate>
<textblock text="{Binding ParameterDisplayName}">

ABitSmart5-Mar-09 5:14

5-Mar-09 5:14

No, he is using DataContext of the parent implicitly.

babongita5-Mar-09 5:23

5-Mar-09 5:23

on a side note this happens with all of the comboboxes, but I have them all coded the same so I have the same issue.

Prajeesh4-Mar-09 17:11

4-Mar-09 17:11

[Message Deleted]

ABitSmart4-Mar-09 17:26

4-Mar-09 17:26

When are you calling OnMouseUp ? Taking a guess, I think you do not need it. Looks like OnMouseDown and OnMouseMove are doing what you want ??

Prajeesh4-Mar-09 17:33

4-Mar-09 17:33

[Message Deleted]

ABitSmart4-Mar-09 17:52

4-Mar-09 17:52

Prajeesh wrote:
StartPoint = Args.GetPosition(PhotoBox);

In the MoveDown event, what is PhotoBox? shouldn't it be DrawingCanvas ?

I did the same thing you are doing, on the MouseMove and MouseLeftButtonDown event of the Canvas, and I never got any extra lines.

Prajeesh4-Mar-09 18:06

4-Mar-09 18:06

[Message Deleted]

ABitSmart4-Mar-09 18:23

4-Mar-09 18:23

private void OnMouseMove(object Sender, MouseEventArgs Args)
{
if (Args.LeftButton == MouseButtonState.Pressed)
{
EndPoint = Args.GetPosition(DrawingCanvas);
DrawLine(StartPoint, EndPoint, DrawingCanvas);
//do not reset the startpoint
//StartPoint = EndPoint;
}
}

And in your DrawLine method, delete the old line before adding the new line.

Prajeesh4-Mar-09 19:12

4-Mar-09 19:12

[Message Deleted]

ABitSmart4-Mar-09 19:21

4-Mar-09 19:21

Searching for the control and removing it from the Children collection.

Something like this,

Line previousLine = null;
foreach (UIElement child in TargetCanvas.Children )
{
    if( child is Line)
    {
        previousLine = child as Line;
        break;
    }
}

if (null != previousLine)
{
    TargetCanvas.Children.Remove(previousLine);
}

please update it to fit your needs.

Prajeesh4-Mar-09 19:42

4-Mar-09 19:42

[Message Deleted]

ABitSmart4-Mar-09 19:48

4-Mar-09 19:48

Yes, I hope you can build ahead from the help you have been provided. What you could do is generate a new line name everytime you start drawing and use that line name in the MoveMouse for adding the new line and also for deleting the existing line.