How to change the header of a WPF datagrid expander according to values in the group the expander is related to?

Question

0.00/5 (No votes)

See more:

Hello,
I am using a CollectionViewSource as ItemSource for a WPF DataGrid to fill and group the DataGrid: (I fill it with data from a database)

C#

dataTable = new CollectionViewSource
{
    Source = Global.dsAuftraege.Tables[0]
};
            
dataTable.GroupDescriptions.Add(new PropertyGroupDescription("Auftragsnummer"));

For the DataGrid Groups I use the following Style:

XML

<Style x:Key="GroupStyle" TargetType="{x:Type GroupItem}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type GroupItem}">
                        <Expander x:Name="expander" IsExpanded="True"
                                  Background="LightBlue"
                                  Foreground="Black">
                            <Expander.Header>
                                <DockPanel>
                                    <TextBlock Style="{StaticResource HeaderTextBlock}" x:Name="ExpanderHeader1" Text="{Binding Name}" Margin="5,0,0,0" Width="200"/>
                                    <TextBlock x:Name="ExpanderHeader2" FontWeight="Normal" Text="{Binding ItemCount}"/>
                                    <TextBlock x:Name="ExpanderHeader3" FontWeight="Normal" Text=""/>
                                </DockPanel>
                            </Expander.Header>
                            <ItemsPresenter/>
                        </Expander>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

As you can see I use an Expander and the Expander.Header consists of 3 TextBlocks. And here comes my problem:
In the underlying database I have a column called "State" containing integers from -1 to 2. My DataGrid shows this column too.
Now I want to make the Expander.Header texts bold when there are rows within the Expanders Group with "State"==2.
What is more: I want to count all the rows within a Group with "State"==2 and show the count in "ExpanderHeader3" TextBlock.

What I have tried:

I tried different approaches in XAML but also in Code behind.

XAML:
I tried different Triggers, but couldn't get it running.

Code behind:
I tried to access the Expander in code behind with VisualTreeHelper, but it did not work.

I think it should be possible to solve this in XAML, but since I am new to it I have no idea how to do it.

I am happy about any suggestion.
Thank you.

Posted 21-Aug-19 3:51am

joni7373

Updated 22-Aug-19 22:36pm

Add a Solution

2 solutions

Solution 1

Add properties (get;set) to your data context for your text block bindings (Name, ItemCount); query your data for the settings; and set the properties.

If done once (in Loaded, for example) may not need to implement an INotifyPropertyChanged interface.

<TextBlock Style="{StaticResource HeaderTextBlock}" x:Name="ExpanderHeader1" Text="{Binding Name}" Margin="5,0,0,0" Width="200"/>
                                    <TextBlock x:Name="ExpanderHeader2" FontWeight="Normal" Text="{Binding ItemCount}"/>
                                    <TextBlock x:Name="ExpanderHeader3" FontWeight="Normal"

Posted 21-Aug-19 5:45am

Gerry Schmitz

Comments

joni7373 22-Aug-19 2:22am

Thank you for the fast reply. But I don't get it. The text block bindings Name and ItemCount work appropiately.
But I want to change their FontWeight Property and the Text Property of "ExpanderHeader3" according to a column in the DataGrid in the different Groups. My problem is therefore I have to look at the data Group-wise and I have no idea how to do this...

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

joni7373 · Accepted Answer · 2019-08-22T22:36:00

I solved it now using Converters for "Text" and "FontWeight" of the TextBoxes in the Expander.Header binding to the Name of the Group like this:

XML

<TextBlock x:Name="ExpanderHeader3" Width="100"  FontWeight="{Binding Path=Name,Converter={StaticResource fontWeightConverter}}" Text="{Binding Path=Name,Converter={StaticResource nameToActiveConverter}}"/>

The Converters go just through my database search for the "Name" and count the rows where "state"==2. Then they return the respective count or FontWeight.

Not quite elegant nor efficient, because I loop over every row of the underlying database, but it does what it is supposed to.