How to: Implement Custom Grouping

• Oct 04, 2021
• 2 minutes to read

In the example below, the grid raises the CustomColumnGroup and CustomColumnSort events to apply a custom grouping and sort algorithm to the Unit Price column.

The control also raises the CustomGroupDisplayText event to change the text within group rows.

ASPX

<dx:ASPxGridView ID="grid" runat="server" AutoGenerateColumns="False" KeyFieldName="ProductID" 
    OnCustomColumnGroup="grid_CustomColumnGroup" 
    OnCustomColumnSort="grid_CustomColumnSort" 
    OnCustomGroupDisplayText="grid_CustomGroupDisplayText">
    <GroupSummary>
        <dx:ASPxSummaryItem SummaryType="Count" />
    </GroupSummary>
    <Columns>
        <dx:GridViewDataTextColumn FieldName="ProductID" ReadOnly="True" VisibleIndex="0">
            <EditFormSettings Visible="False" />
        </dx:GridViewDataTextColumn>
        <dx:GridViewDataTextColumn FieldName="ProductName" VisibleIndex="1" />
        <dx:GridViewDataTextColumn FieldName="UnitPrice" VisibleIndex="2" GroupIndex="0" SortIndex="0"
            SortOrder="Ascending">
            <PropertiesTextEdit DisplayFormatString="c" />
            <Settings AllowDragDrop="False" SortMode="Custom" />
        </dx:GridViewDataTextColumn>
        <dx:GridViewDataCheckColumn FieldName="Discontinued" VisibleIndex="3" />
    </Columns>
    <Settings ShowGroupedColumns="True" ShowGroupPanel="True" />
</dx:ASPxGridView>

C#

protected void grid_CustomColumnSort(object sender, DevExpress.Web.ASPxGridView.CustomColumnSortEventArgs e) {
    CompareColumnValues(e);
}

protected void grid_CustomColumnGroup(object sender, DevExpress.Web.ASPxGridView.CustomColumnSortEventArgs e) {
    CompareColumnValues(e);
}

private void CompareColumnValues(DevExpress.Web.ASPxGridView.CustomColumnSortEventArgs e) {
    if(e.Column.FieldName == "UnitPrice") {
        int res = 0;
        double x = Math.Floor(Convert.ToDouble(e.Value1) / 10);
        double y = Math.Floor(Convert.ToDouble(e.Value2) / 10);
        res = Comparer.Default.Compare(x, y);
        if(res < 0) res = -1;
        else if(res > 0) res = 1;
        if(res == 0 || (x > 9 && y > 9)) res = 0;

        e.Result = res;
        e.Handled = true;
    }
}

protected void grid_CustomGroupDisplayText(object sender, DevExpress.Web.ASPxGridView.ASPxGridViewColumnDisplayTextEventArgs e) {
    if(e.Column.FieldName == "UnitPrice") {
        double d = Math.Floor(Convert.ToDouble(e.Value) / 10);
        string displayText = string.Format("{0:c} - {1:c} ", d * 10, (d + 1) * 10);
        if(d > 9) displayText = string.Format(">= {0:c} ", 100);
        e.DisplayText = displayText;
    }
}

VB.NET

Protected Sub grid_CustomColumnSort(ByVal sender As Object, ByVal e As DevExpress.Web.ASPxGridView.CustomColumnSortEventArgs)
    CompareColumnValues(e)
End Sub

Protected Sub grid_CustomColumnGroup(ByVal sender As Object, ByVal e As DevExpress.Web.ASPxGridView.CustomColumnSortEventArgs)
    CompareColumnValues(e)
End Sub

Private Sub CompareColumnValues(ByVal e As DevExpress.Web.ASPxGridView.CustomColumnSortEventArgs)
    If e.Column.FieldName = "UnitPrice" Then
        Dim res As Integer = 0
        Dim x As Double = Math.Floor(Convert.ToDouble(e.Value1) / 10)
        Dim y As Double = Math.Floor(Convert.ToDouble(e.Value2) / 10)
        res = Comparer.[Default].Compare(x, y)

        If res < 0 Then
            res = -1
        ElseIf res > 0 Then
            res = 1
        End If

        If res = 0 OrElse (x > 9 AndAlso y > 9) Then res = 0
        e.Result = res
        e.Handled = True
    End If
End Sub

Protected Sub grid_CustomGroupDisplayText(ByVal sender As Object, ByVal e As DevExpress.Web.ASPxGridView.ASPxGridViewColumnDisplayTextEventArgs)
    If e.Column.FieldName = "UnitPrice" Then
        Dim d As Double = Math.Floor(Convert.ToDouble(e.Value) / 10)
        Dim displayText As String = String.Format("{0:c} - {1:c} ", d * 10, (d + 1) * 10)
        If d > 9 Then displayText = String.Format(">= {0:c} ", 100)
        e.DisplayText = displayText
    End If
End Sub