Ticket T554628

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Change cell background color through code

Marc Seguin 1

created 8 years ago

I'm looking for a way to change the background color for a cell through code, or maybe a better way to accomplish my goal.

I have a grid with multiple columns. Some of the columns aren't used depending on the value of other columns. So for example, I have a grid to define some fields that will be added to a table in a database. The first column is to select the data type, which will be Text or Numeric. I then have a column for Text Length, where the user will enter the max length for text in the field. If the user picks Numeric as the type, the Text Length cell, for that row, needs to be locked so the user can't enter anything.

To do this in a generic way, I use the OnCustomColumnDisplayText event in my grid and added a IsValueRequired(string fieldName) method in my model. If the IsValueRequired method returns false, I set the display text to string.empty. I also use the OnShowingEditor event to disable showing the editor if IsValueRequired returns false.

This works perfectly and I can show a blank value where the value isn't required and the cell is disabled so the user can't click into.

To make it more obvious to the user that the cell won't allow input, I would like to change the cell background color to grey.

Is it possible to do this trough code with the grid events? If not, is it possible to do this with a style? If it's a style, I'm not sure what I would use as the trigger for how the cell is displayed.

In some other places we we ShowAsNullText in OnCustomColumnDisplayText. Is there a way to change the cell style base on whether ShowAsNullText is being used in the cell?

Thanks for any help you can provide. I can throw together a quick example app if needed.

Answers approved by DevExpress Support

Alex Chuev (DevExpress)

created 8 years ago (modified 8 years ago)

Hi Marc,

You can use the CustomCellAppearance event to conditionally set the cell background in code.

C#
private void view_CustomCellAppearance(object sender, DevExpress.Xpf.Grid.CustomCellAppearanceEventArgs e) {  
    if (e.Property == TextElement.BackgroundProperty && !((Item)grid.GetRow(e.RowHandle)).IsValueRequired(e.Column.FieldName)) {  
        e.Result = Brushes.LightGray;  
        e.Handled = true;  
    }  
}

I've attached a sample project that demonstrates this approach in action.

Thanks,
Alex

dxSample.zip

Show previous comments (9)

Marc Seguin 1 8 years ago

Looks like the wrong sample was attached. The example has something to do with PdfCommandProvider.

Also, I think I tagged the wrong component. I'm using GridControl in WPF. I'm not sure if that event is part of GridControl.View. I didn't see it.

Marc Seguin 1 8 years ago

Sorry, I was able to find the CustomCellAppearance event. I just had to cast the View to a TableView.

((TableView)View).CustomCellAppearance += OnCustomCellAppearance;

I'm doing some testing now, but it would be good to get the correct sample.

Marc Seguin 1 8 years ago

Ok, I kind of have it working. In my small test app it's working perfectly. In my actual application, I can see that it's going into the event and setting the background value when it should, but for some reason in my main app I don't see the updated background color of the cells till I select the row. So as I select each row, it will update the background color on the correct fields.

Any thoughts on why this would be? I can't reproduce this issue in my test app.

Alex Chuev (DevExpress) 8 years ago

Hi Marc,

My apologies for sending an incorrect project. I've updated the attachment in my previous post.

As for your working project, it is strange that the same approach does not work there. Do you use any custom styles/templates in your grid? Do your objects implement the INotifyPropertyChanged interface? Also, does the event fire before you select a row, or does it only fire after the selection?

Thanks,
Alex

Marc Seguin 1 8 years ago

I'm still investigating. It is working on most grids. I have a few that are causing the above issue where the background of the cells only changes when the rows are selected. We use quite a few templates and a band provider for our grids so it's difficult to pull it out into a test app. So far I haven't found the difference between the grids that are working and the ones that aren't. I'll have to keep poking around.

Andrey Marten (DevExpress Support) 8 years ago

Hello Marc,

I hope you don't mind if I join this conversation.

According to your description, corresponding GridControls may use different styles and templates and I suggest that you try disabling them all and check if this helps. If so, apply templates separately to determine the problematic one. Additionally, check if the issue is specific only to GridControls with bands. If so, send us corresponding code and XAML files. This will help us find the cause of the issue and suggest a more suitable solution. Note that you can mark this thread Private and only my colleagues and I will have access to it.

Marc, you also did not clarify if your data objects implements the INotifyPropertyChanged interface. Please check if this condition is met, since this is required in such scenarios.

I look forward to your response.

Thanks,
Andrey

Marc Seguin 1 8 years ago

I've narrowed it down and have been able to reproduce the issue in the attached sample (modification of the sample provided to me in this case).

We've created a GridControlEx class that extends GridControl. In GridControlEx, we handle the CustomCellAppearance, CustomColumnDisplayText, and ShowingEditor events. We attach handlers to these events in the Loaded event.

If you run the attached example, you will see that the background color is only updated in the first row. The other rows that have Data Type = Numeric still have white backgrounds. Also, the DisplayText should be string.Empty for the Numeric rows, but it isn't.

I noticed that if I click any of the column headers to sort the grid, all of the Text Length cells show the correct background color and DisplayText.

I added a call to RefreshData at the end of the Loaded event and this has fixed the problem. This line is commented out in the attached example so that you can see the issue. If you uncomment this line, you will see the cells are displayed properly when the form is loaded.

So my question is, should I leave this call to RefreshData in there or maybe I should attach handlers to the events in an event that fires before Loaded?

Thanks,
Marc

dxSample_Updated.zip

Kirill (DevExpress Support) 8 years ago

Hello,
This issue occurs because you're subscribing to events when GridControl is loaded. In your case, when the Loaded event is raised, GridControl is fully populated with items. To resolve this issue, I suggest your subscribe to events using GridControl's constructor and the OnViewChanged method. I've modified your sample project to demonstrate this approach.

Thanks,
Kirill

dxSample_U...dated2.zip

Marc Seguin 1 8 years ago

I made these changes in GridControlEx in our main application and confirmed the grid is now updated correctly on load.

Thanks for the updated example.

Cheers,
Marc

Kirill (DevExpress Support) 8 years ago

You are welcome!

Amit Singh 5 years ago

Hi Kirill,

I am having problem setting cell color on cell value change. I am able to set the color in code but it is not reflecting on the cell right away.

I am using below code :-

private void view_CellValueChanged(object sender, DevExpress.Xpf.Grid.CellValueChangedEventArgs e)
{
var view = NominationGrid.View as TableView;
if (view != null)
{

if (e.Column.FieldName.Split('.').Last() == "Status")
{
string cellValue = e.Value.ToString();
if (cellValue == "Rejected")
((DataViewBase)sender).Background = Brushes.LightBlue;

}

view.CommitEditing();
return;
}
}
And used it in xaml like below : (Ignore PFWGridControl as we made a user control inherited from GridControl of DevExpress.Xpf.Grid)

edx:PFWGridControl.View
<dxg:TableView ShowGroupPanel="False" CellStyle="{StaticResource NominationGridCellStyle}" CellValueChanged="view_CellValueChanged">
<!–dxg:TableView.FormatConditions
<dxg:FormatCondition ValueRule="Equal" Value1="0" FieldName="RowData.Row.Status" PredefinedFormatName="LightRedFill"/>
</dxg:TableView.FormatConditions>–>
</dxg:TableView>
</edx:PFWGridControl.View>

I used NominationGridCellStyle as a resource which only work when screen get reopen after changed data which is fine.

Thanks,
Amit

Dima (DevExpress Support) 5 years ago

Hello Amit,

Not to mix different questions in one thread, I created a separate ticket on your behalf - How to change a cell background color when its value changes. It has been placed in our processing queue and will be answered shortly.

Created: September 12, 2017 10:12 PM

Modified: February 13, 2020 3:18 PM

Platform: WPF

Product: DXGrid and DXTreeList for WPF

Build: 16.2.6

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Change cell background color through code

Answers approved by DevExpress Support

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