Changing the GroupByExpression on dynamic grouping

[erwin]

In my sample grid, I would like to allow grouping by the user, but add a count(fieldname) aggreagate to the groupbyexpression.
I found examples for the ASP.NET Grid but could not directly apply these to the WinForms Grid.

regards
erwin

[Jack]

Hello Erwin,

Thanks for the good question.

Yes, you can achieve the required functionality. You should handle the GroupingChanging event and add the required aggregate to the SelectedFields collection of the new GridGroupByExpression. Note that adding a new aggregate will change the collection again and the event will be fired one more time. This could lead to an infinite recursion, i.e. stack overflow. One way to avoid that is to implement a flag that controls the recursive call.

Please refer to the following example:

	private bool addingAggregate = false;
	public Form1()
	{
	InitializeComponent();
	this.radGridView1.GroupByChanging += new GridViewCollectionChangingEventHandler(radGridView1_GroupByChanging);
	}
	private void radGridView1_GroupByChanging(object sender, GridViewCollectionChangingEventArgs e)
	{
	if (addingAggregate) return;
	GridGroupByExpression expression = e.NewItems[0] as GridGroupByExpression;
	if (expression == null)
	return;
	addingAggregate = true;
	GridGroupByField field = new GridGroupByField(expression.SelectFields[0].FieldName);
	field.Aggregate = GridAggregateFunction.Count;
	expression.SelectFields.Add(field);
	addingAggregate = false;
	}

I hope this helps. Should you have further questions, do not hesitate to ask.

Best wishes,
Jack
the Telerik team

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[erwin]

Thanks, this is what I needed. Had to add an additional test to your code to make it crash proof:

if(e.NewItems=null) return;

[Jack]

Hi erwin,

You are correct, thank you for this correction.

I am glad to hear that the issue is now resolved. Do not hesitate to contact me again if you have other questions.

Best wishes,
Jack
the Telerik team

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[erwin]

The sample code provided does not work correctly when the column contains
NULL cells. The Grouping works, that is all rows that have a NULL value
are grouped together, but the aggreagte COUNT() function returns 0 ,
even if the group contains several rows.

[Julian Benkov]

Hi Erwin,

The current implementation and design of the Count aggregate ignores rows with NULL values, although we do plan to redesign this behavior.

Currently you can use a solution with the RagGridView GroupSumaryEvaluate event:

void radGridView1_GroupSumaryEvaluate(object sender, GroupSummaryEvaluationEventArgs e)
{
    if (e.SummaryItem.Aggregate == GridAggregateFunction.Count)
    {
        e.Value = e.Group.RowCount;
    }
}

All the best,
Julian Benkov
the Telerik team

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[erwin]

Hi Julian,

your solution is just what I needed - thanks a lot.

Regards
Erwin

[erwin]

Grids that have this mechanism enabled, seem to have problems using SaveLaout() / LoadLayout()

I have of course added a flag, that suppresses the GroupByChanging event being handled when caused by LoadLayout.

When I do a SaveLayout() and then a LoadLayout() the group captions (combined format strigs) seem to duplicate.

       static void grid_GroupByChanging(object sender, GridViewCollectionChangingEventArgs e)
        [
            if (_addingAggregates)
            [
                return;
            ]

            if(_loadingLayout)
            [
                return;
            ]

            if(e.NewItems == null)
            [
                return;
            ]

            if(e.NewItems.Count<1)
            [
                return;
            ]

            GridGroupByExpression expression = e.NewItems[0] as GridGroupByExpression;

            if (expression == null)
                return;

            if(expression.SelectFields==null)
            [
                return;
            ]

            if(expression.SelectFields.Count<1)
            [
                return;
            ]

            try
            [
                _addingAggregates = true;
                expression.SelectFields[0].FormatString = "[0]: [1]";
                GridGroupByField field = new GridGroupByField(expression.SelectFields[0].FieldName);
                field.Aggregate = GridAggregateFunction.Count;
                field.FormatString = " ([1])";
                expression.SelectFields.Add(field);
            ]
            finally
            [
                _addingAggregates = false;
            ]
        ]

        static public bool LoadLayout(RadGridView grid)
        [
            GridInfo info = grid.Tag as GridInfo;

            if (info == null)
            [
                return false;
            ]

            string savePath = System.Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
            savePath += `"\Octosoft\Octopus\GridLayouts";

            savePath += `"\" + info.Guid.ToString() + ".xml";

            if(File.Exists(savePath))
            [
                try
                [
                    Debug.Assert(grid.Tag == info);
                    _loadingLayout = true;
                    grid.LoadLayout(savePath);
                    //MessageBox.Show(grid.Tag.GetType().ToString() + ":" +grid.Tag.ToString());
                    //Debug.Assert(grid.Tag == info);
                    // have to re-set the Tag object, since it got destroyed by LoadLayout
                    //TODO: BUG in 2008Q3SP1 TicketID 181002
                    grid.Tag=info;
                    return true;
                ]
                catch (System.Exception ex)
                [
                    ErrorMessage.Show("Error Loading Grid Layout: " + savePath, ex);
                    File.Delete(savePath);
                    return false;
                ]
                finally
                [
                    _loadingLayout = false;
                ]
            ]
            return false;
        ]

[Boyko Markov]

Hi erwin,

Thank you very much about your valuable feedback. I am afraid that this behavior can not be avoided in an easier way than you already found. When saving loading/layout grid view persists all related object, like the group-by expressions. After loading the xml with group-expressions persisted, you should not add the custom group-by count field - as you already figured it out.
The other option would be to exclude all the group-by expressions from persistence if this fits in your scenario.

Greetings,
Boyko Markov
the Telerik team

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[erwin]

Boyko,

thanks for the response - what I meant is that despite of my efforts, the grid does not save/load layouts correctly in my scenario. Some of the definitions seem to get duplicated on either Save or Load.
I have filed a bug report with a stripped down sample project that exposes the bug.

Regards
Erwin

[Nick]

Hello erwin,

Please refer to the sample application that I send to you in one of your previous tickets about the Tag property (Ticket Id: 181002).

Sincerely yours,
Nick
the Telerik team

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[erwin]

Thank you, Nick

I've implemented the suggested workaround.

Regards & Happy Holidays

Erwin

[Dragoljub]

I am having the same issue with an aggregate in the group by expression and load layout. The whole expression gets duplicated. Can you post an example of how to avoid this?

[Nick]

Hi Dragoljub,

Thank you for your question. I have attached the sample application I sent to Erwin. I hope this helps.

Do not hesitate to contact me back if you have more questions.

All the best,
Nick
the Telerik team

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[Dragoljub]

Hello,

Dim stringWriter As New IO.StringWriter()

Using xmlWriter As New Xml.XmlTextWriter(stringWriter)

serializer.WriteObjectElement(xmlWriter, radGrid)

xmlWriter.Close()   ' important line - it creates the closing tag for the root element

End Using

Return stringWriter.ToString()

In that code I get an exception on serializer.WriteObjectElement(xmlWriter, radGrid): "Index was outside the bounds of the array.".
Stack trace:
"   at System.Xml.XmlTextWriter.WriteEndStartTag(Boolean empty)    at System.Xml.XmlTextWriter.AutoComplete(Token token)    at System.Xml.XmlTextWriter.WriteStartElement(String prefix, String localName, String ns)    at System.Xml.XmlWriter.WriteNode(XmlReader reader, Boolean defattr)    at Telerik.WinControls.XmlSerialization.ComponentXmlSerializer.WriteObjectElement(XmlWriter writer, Object toWrite)    at ...

I don't know what I did wrong. I just know that it does not work even when I deleted the old stored layout. Can it be a different version of RadGrid? I am using: Q3 2008 (8.1.0.0 when browsed in references).

[Dragoljub]

I meant Q3 2008 SP1 (just didn't see the "SP1" on the start menu folder, it was cut off).

[Dragoljub]

I just read the newsletter and there's an SP2 release! It says "RadGridView: introduced an API for customizing XML Serialization", so maybe that's the thing? Your code works for the new version only?

[MiroslavStantic]

[Dragoljub]

No, I tried it with the new version (uninstalled the previous one first of course) and still get that same error.

What is "API for customizing XML Serialization" and how do I use that? Maybe that can help...

[Mike]

Hello Dragoljub,

Thank you for contacting me back.
Yes indeed, we introduced new API that much simplifies the tweaking the serialization in SP2.
Here is sample code (modified version of a snipped from the previously attached sample):

Me.radGridView1.XmlSerializationInfo.SerializationMetadata.Add(GetType(Control), "Tag", New DesignerSerializationVisibilityAttribute(DesignerSerializationVisibility.Hidden))
Me.radGridView1.XmlSerializationInfo.SerializationMetadata.Add(GetType(GridViewTemplate), "SummaryRowGroupHeaders", New DesignerSerializationVisibilityAttribute(DesignerSerializationVisibility.Hidden))
'here you may exclude/include other properties.

Me.radGridView1.SaveLayout(sfd.FileName)

Note you you are no longer required to use GridLayoutSerializer. Now you can just modify the serialization metadata it uses. You need to do this customization only once per grid instance.

Let me know if this helped.

All the best,
Mike
the Telerik team

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[Dragoljub]

Thanks, it helped. Now it saves without that nasty exception.

[Mike]

Hi Dragoljub,

I am glad it helped.
In case you want to learn more about grid settings persistence, we just post a KB article and demo project that is wort having a look at:
http://blogs.telerik.com/blogs/09-02-03/RadGridView_s_Serialization_Made_Easy_WinForms.aspx

In short, the article describes a way to let the end user specify which grid settings should be persisted and which should not.

All the best,
Mike
the Telerik team

Check out Telerik Trainer, the state of the art learning tool for Telerik products.

[Emix]

Hi Team

I would like to get complete code for grouping multiple columns when user clicks on "checkbox", but not on "radgridview". I now how to add grouping descriptor dynamically. But when I select any single item(checkbox) for grouping, it works great. But if i am going to select more than one item together, I am getting an Error message as shown in "error" Picture. Also I want to enable or disable grouping through check box only, that is when user click on "checkbox" corresponding item will get grouped.
Hope I will get solution soon....(VB.net code snippette)

    Dim STO_Group_One As New GroupDescriptor()
    Dim STO_Group_Two As New GroupDescriptor()

Private Sub GridFilter_ProName_CBX_ToggleStateChanged(ByVal sender As System.Object, ByVal args As Telerik.WinControls.UI.StateChangedEventArgs) Handles GridFilter_ProName_CBX.ToggleStateChanged

        If GridFilter_ProName_CBX.Checked = True Then
            If Me.STO_ReportGrid.GroupDescriptors.Count = 0 And Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProName") = False Then
                STO_Group_One.GroupNames.Add("PRProName", ListSortDirection.Ascending)
                Me.STO_ReportGrid.GroupDescriptors.Insert(0, STO_Group_One)
            ElseIf Me.STO_ReportGrid.GroupDescriptors.Count = 1 And Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProName") = False Then
                STO_Group_One.GroupNames.Add("PRProName", ListSortDirection.Ascending)
                Me.STO_ReportGrid.GroupDescriptors.Insert(1, STO_Group_One)
                Exit Sub
            End If
        Else

        End If
        If GridFilter_ProName_CBX.Checked = False Then
            If Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProName") = True Then
                Me.STO_ReportGrid.GroupDescriptors.Remove(STO_Group_One)
            End If
        End If

    End Sub



    Private Sub GridFilter_ProCat_CBX_ToggleStateChanged(ByVal sender As System.Object, ByVal args As Telerik.WinControls.UI.StateChangedEventArgs) Handles GridFilter_ProCat_CBX.ToggleStateChanged

        If GridFilter_ProCat_CBX.Checked = True Then
            If Me.STO_ReportGrid.GroupDescriptors.Count = 0 And Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProCat") = False Then
                STO_Group_Two.GroupNames.Add("PRProCat", ListSortDirection.Ascending)
                Me.STO_ReportGrid.GroupDescriptors.Insert(0, STO_Group_Two)
            ElseIf Me.STO_ReportGrid.GroupDescriptors.Count = 1 And Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProCat") = False Then
                STO_Group_Two.GroupNames.Add("PRProCat", ListSortDirection.Ascending)
                Me.STO_ReportGrid.GroupDescriptors.Insert(1, STO_Group_Two)
                Exit Sub
            End If
        End If
        If GridFilter_ProCat_CBX.Checked = False Then
            If Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProCat") = True Then
                Me.STO_ReportGrid.GroupDescriptors.Remove(STO_Group_Two)
            End If
        End If

    End Sub


    Private Sub STO_ReportGrid_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles STO_ReportGrid.GroupByChanging

        On Error Resume Next
        If Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProName") = True Then
            Me.GridFilter_ProName_CBX.Checked = False
        ElseIf Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProCat") = True Then
            Me.GridFilter_ProCat_CBX.Checked = False
        End If
    End Sub

[Julian Benkov]

Hello Emix,

You can add a second descriptor by using the Add method of the GroupDescriptors in your scenario:

If GridFilter_ProName_CBX.Checked = True Then
    If Me.STO_ReportGrid.GroupDescriptors.Count = 0 And Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProName") = False Then
        STO_Group_One.GroupNames.Add("PRProName", ListSortDirection.Ascending)
        Me.STO_ReportGrid.GroupDescriptors.Insert(0, STO_Group_One)
    ElseIf Me.STO_ReportGrid.GroupDescriptors.Count = 1 And Me.STO_ReportGrid.GroupDescriptors.Expression.Contains("PRProName") = False Then
        STO_Group_One.GroupNames.Add("PRProName", ListSortDirection.Ascending)
        Me.STO_ReportGrid.GroupDescriptors.Add(STO_Group_One)
        Exit Sub
    End If
Else

End If

To remove close buttons from the GroupPanel you can process the GroupChanged event and collapse all RemoveButton instances:

Private Sub gridView_GroupByChanged(sender As Object, e As GridViewCollectionChangedEventArgs)
    Dim templateGroupsElement As TemplateGroupsElement = Me.gridView.GridViewElement.FindDescendant(Of TemplateGroupsElement)()
    If templateGroupsElement IsNot Nothing Then
        For Each element As RadElement In templateGroupsElement.Children
            Dim groupElement As GroupElement = TryCast(element, GroupElement)
            If groupElement IsNot Nothing Then
                For Each fieldElement As GroupFieldElement In groupElement.GroupingFieldElements
                    fieldElement.RemoveButton.Visibility = ElementVisibility.Collapsed
                Next
            End If
        Next
    End If
End Sub

I hope this helps. Feel free to ask if you have any additional questions.

Kind regards,
Julian Benkov
the Telerik team