Nevron Open Vision Documentation
Grouping

 
About Grouping

Grouping is only applicable for Table Grid. Grouping is performed after filtering as described in the Data Processing Overview topic. The purpose of grouping is to create a hierarchical organization of the grid rows, such that the rows that reside in each group share some common grouping defined common value.

The groupings of a Table Grid are defined as a collection of NGroupingRule instances that are contained inside a NGroupingRuleCollection accessible from the NTableGrid.GroupingRules property. Because the Table Grid can have multiple grouping rules, this helps you create hierarchical grids like the one in the following image:

figure 1. Hierarchical Grid

 

The NGroupingRule exposes control over the following aspects of the grouping:

The rest of this topic discusses these aspects in detail

Grouping Rule and its Row Value

There is a Row Value associated with each NGroupingRule. The row value is specified by the RowValue property. The purpose of the row value is to define the criteria by which rows are grouped at each specific grouping level. The following code example creates several grouping rules that group by two different data source fields:

NGroupingRule and Row Value Example
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NGroupingRule groupByJobTitle = new NGroupingRule();
groupByJobTitle.RowValue = new NFieldRowValue("JobTitle");
tableGrid.GroupingRules.Add(groupByJobTitle);
NGroupingRule groupByName = new NGroupingRule();
groupByName.RowValue = new NFieldRowValue("Name");
tableGrid.GroupingRules.Add(groupByName);
The general rule of grouping is that two records belong to the same group, if the grouping rule RowValue produces the same value for these records. That is why the RowValue determines the way in which the grouping works. See Row Values for more information.
Grouping Rule and the associated Column

Each grouping rule can be associated with a grid column. The associated column is specified by the NGroupingRule.Column property. There are several things, which happen when a filtering rule is associated with a column:

When a column is dragged to the grouping panel, the column is asked to create a grouping rule. By default the column creates a grouping rule that is simply associated the column itself, as shown by the "Group By Column" example. You can however intercept the NColumn.CreateGroupingRuleDelegate delegate to create a custom grouping rule, when the column is dropped in the Groupings Panel

Custom Column Grouping Rule
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column.CreateGroupingRuleDelegate = delegate(NColumn theColumn)
{
    NGroupingRule groupingRule = new NGroupingRule();
    NCustomRowValue<string> rowValue = new NCustomRowValue<string>();
    rowValue.GetRowValueDelegate = delegate(NCustomRowValueGetRowValueArgs<string> getValueArgs)
    {
        switch (Convert.ToString(getValueArgs.DataSource[getValueArgs.Row, "Country"]))
        {
            case "USA":
            case "Canada":
                return "North America";
            case "Germany":
            case "France":
                return "Europe";
            default:
                return "Unknown";
        }
    };
    groupingRule.RowValue = rowValue;
    return groupingRule;
};
Grouping Panel and Grouping Headers

Each grouping rule that resides in the NGrid.GroupingRules collection is represented by a grouping header in the grouping panel. The following image shows a Grouping Panel with two grouping headers:


figure 3. Grouping Panel and Grouping Headers

The grouping header is represented by an instance of the NGroupingHeader class, which has a Content widget and Sort Order and Remove buttons. The Sort Order button toggles the grouping NGroupingRule.SortingDirection. The Remove button removes the grouping rule from the NGrid.GroupingRules collection.

The grouping rule is responsible for the creation of the grouping header. When the grouping rule is asked to create a grouping header to represent it in the groupings panel, it raises the CreateGroupingHeaderContent event, which allows you to customize the grouping header. If the user does not handle the CreateGroupingHeaderContent event, by default the content of the grouping header is the same as the column header content and is created by the column. The following code example customizes the grouping header:

Custom Grouping Header Content
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NGroupingRule groupingRule = new NGroupingRule();
groupingRule.CreateGroupingHeaderContent += delegate(NCreateGroupingRuleGroupingHeaderContentArgs arg)
{
    NPairBox pair = new NPairBox("Birthday", NResources.Image__16x16_Birthday_png);
    arg.GroupingHeaderContent = pair;
};
Group Rows

Each group of records is headered by a NGroupRow, which is a row that consists of span cells. You can customize the cells that appear in group row created by the grouping rule, by handling the NGroupingRule.CreateGroupRowCells event:

Custom GroupRow cells
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NGroupingRule groupingRule = new NGroupingRule();
groupingRule.CreateGroupRowCells += delegate(NCreateGroupingRuleGroupRowCellsArgs arg)
{
    string country = Convert.ToString(arg.GroupRow.GroupValue);
    NGroupRowCell countryCell = new NGroupRowCell(country);
    countryCell.EndXPosition.Mode = ENSpanCellEndXPositionMode.NextCellBeginX;
    NGroupRowCell ordersCountCell = new NGroupRowCell("Orders Count:" + arg.GroupRow.Recordset.Count);
    ordersCountCell.EndXPosition.Mode = ENSpanCellEndXPositionMode.RowEndX;
    ordersCountCell.BeginXPosition.Mode = ENSpanCellBeginXPositionMode.AnchorToEndX;
    arg.GroupRowCells = new NGroupRowCell[] { countryCell, ordersCountCell };
};

See Group Rows and Span Cells for more information about NGroupRow and the NGroupRowCell.

Grouping Rules created by Columns

When a column is dropped in the grouping panel, the column is asked to create a grouping rule that represents this column. By default the column simply creates a grouping rule that is associated with the column (e.g. groups by the column values). You may however want to perform custom grouping for specific columns. In order to do that you need to handle the NColumn.CreateColumnGroupingRule event as shown in the following example:

Custom grouping rules created by columns
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column.CreateColumnGroupingRule += delegate(NCreateColumnGroupingRuleEventArgs arg)
{
    // create a custom sorting rule
    NGroupingRule groupingRule = new NGroupingRule();
    NCustomRowValue<string> customRowValue = new NCustomRowValue<string>();
    customRowValue.GetRowValueDelegate = delegate(NCustomRowValueGetRowValueArgs<string> args)
    {
        DateTime received = Convert.ToDateTime(args.DataSource[args.Row, "Received"]);
        DateTime now = DateTime.Now;
        if (received.Year == now.Year && received.Month == now.Month && received.Day == now.Day)
        {
            return "Received Today";
        }
        else
        {
            return "Not Received Today";
        }
    };
    groupingRule.RowValue = customRowValue;
    // set that rule as event result
    arg.GroupingRule = groupingRule;
};
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