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TreeList.GetCustomSummaryValue Event

Enables you to perform custom summary value calculations.

Namespace: DevExpress.XtraTreeList

Assembly: DevExpress.XtraTreeList.v19.2.dll

Declaration

public event GetCustomSummaryValueEventHandler GetCustomSummaryValue

Event Data

The GetCustomSummaryValue event's data class is GetCustomSummaryValueEventArgs. The following properties provide information specific to this event:

Property Description
Column Obtains the Tree List column used by the summary calculations.
CustomValue Gets or sets a value to be displayed within a summary.
IsSummaryFooter Gets a value indicating whether the total or group summary value is to be calculated.
Nodes Gets the nodes collection for which to calculate a custom summary.

Remarks

The summary feature calculates the result of an aggregate function applied to column values. There are two types of summaries that can be used as described below.

There are 5 summary functions provided by the Tree List control. However, you can implement your own logic for summary calculations by setting the TreeListColumn.SummaryFooter or TreeListColumn.RowFooterSummary property to SummaryItemType.Custom. In this instance, the GetCustomSummaryValue event fires each time the summary value needs to be obtained.

The value to be displayed must be assigned to the GetCustomSummaryValueEventArgs.CustomValue parameter of the event. Mainly, you will have to visit each node affected by the summary in order to perform calculations. This can be done in the following ways depending on the summary type:

Examples

The following sample code declares a new node operation class. This class can be used to calculate the number of nodes in which the specified field value is greater than the predefined limit. The code also handles the TreeList.GetCustomSummaryValue event. This is used to calculate the number of nodes that have a value greater than 500,000 in the Budget field.

Note: you must set a column's TreeListColumn.SummaryFooter property to SummaryItemType.Custom to make use of the TreeList.GetCustomSummaryValue event.

using DevExpress.XtraTreeList;

// declaring the custom operation class
public class TreeListExceedLimitOperation : TreeListOperation {
   private string fieldName;
   private int upperLimit;
   private int result;

   public TreeListExceedLimitOperation(string fieldName, int upperLimit) {
      this.fieldName = fieldName;
      this.upperLimit = upperLimit;
      result = 0;
   }
   // incrementing the counter if the node's value exceeds the limit
   public override void Execute(TreeListNode node) {
      int nodeValue = Convert.ToInt32(node[fieldName]);
      if (nodeValue > upperLimit)
         result++;
   }
   public int Result {
      get { return result; }
   }
}

// ...
// using the created class to calculate the number of nodes
// that have a value greater than 500000 in their Budget field
private void treeList1_GetCustomSummaryValue(object sender, GetCustomSummaryValueEventArgs e) {
   if (e.IsSummaryFooter) {
      TreeListExceedLimitOperation operation = 
        new TreeListExceedLimitOperation("Budget", 500000);
      treeList1.NodesIterator.DoOperation(operation);
      e.CustomValue = operation.Result;
   }
}
See Also