Group Modes and Custom Grouping

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Group Modes

Interval grouping

By default, when grouping by date/time values, only the date portion of values is taken into account, while the time portion is ignored. Rows that contain matching date portions, but different time portions in a grouping column, are combined into a single group.

The default grouping logic is used if grouping columns contain other data types. In this instance, rows are combined into a single group, if they have a matching value in a grouping column.

The Interval Grouping feature allows you to change the default logic. Use the column’s GridColumn.GroupInterval property to specify the required grouping mode.

The image below shows how the data rows can be arranged by the month or year part of a date/time value, or grouped by the first characters.

IntervalGrouping

Merged Grouping

Set the GridViewBase.AllowMergedGrouping property to true to enable the Merged Grouping feature which allows grouping grid data by multiple columns at once.

MergedGrouping

Merged grouping can work in the following modes that you can specify using the GridViewBase.MergedGroupingMode property:

Mode Description
MergedGroupingMode.CtrlKeyPressed (default mode) End-users should hold the Ctrl key pressed when dragging column headers into the group panel to merge groups.
MergedGroupingMode.Always Grid always merges groups when end-users drag column headers into the group panel.

Custom Grouping

You can implement custom logic if the built-in grouping modes do not suit your requirements. Set the ColumnBase.SortMode property to Custom and handle the GridControl.CustomColumnGroup event.

You can handle the GridControl.CustomGroupDisplayText event to change the default text displayed within group rows.

Example

The following example shows how to apply custom rules to group rows. When you group data by the Unit Price column, rows in this column that have values between 0 and 10 are combined into a single group. Rows whose values fall between 10 and 20 are combined into another group, and so forth.

DevExpress WPF | Grid Control - Custom Group Rules

View Example: How to Apply Custom Rules to Group Rows

<dxg:GridControl x:Name="grid" 
                 CustomColumnGroup="OnCustomColumnGroup" 
                 CustomGroupDisplayText="OnCustomGroupDisplayText">
    <dxg:GridControl.Columns>
        <dxg:GridColumn FieldName="FirstName" />
        <dxg:GridColumn FieldName="LastName" />
        <dxg:GridColumn FieldName="UnitPrice" SortMode="Custom" GroupIndex="0">
            <dxg:GridColumn.EditSettings>
                <dxe:SpinEditSettings DisplayFormat="c2" />
            </dxg:GridColumn.EditSettings>
        </dxg:GridColumn>
    </dxg:GridControl.Columns>
    <dxg:GridControl.View>
        <dxg:TableView AutoWidth="True" ShowGroupedColumns="True"/>
    </dxg:GridControl.View>
</dxg:GridControl>
void OnCustomColumnGroup(object sender, CustomColumnSortEventArgs e) {
    if(e.Column.FieldName != "UnitPrice")
        return;
    double x = Math.Floor(Convert.ToDouble(e.Value1) / 10);
    double y = Math.Floor(Convert.ToDouble(e.Value2) / 10);
    e.Result = x > 9 && y > 9 ? 0 : x.CompareTo(y);
    e.Handled = true;
}

void OnCustomGroupDisplayText(object sender, CustomGroupDisplayTextEventArgs e) {
    if(e.Column.FieldName != "UnitPrice")
        return;
    string interval = IntervalByValue(e.Value);
    e.DisplayText = interval;
}

// Gets the interval which contains the specified value.
private string IntervalByValue(object val) {
    double d = Math.Floor(Convert.ToDouble(val) / 10);
    string ret = string.Format("{0:c} - {1:c} ", d * 10, (d + 1) * 10);
    if(d > 9)
        ret = string.Format(">= {0:c} ", 100);
    return ret;
}
See Also