TreeListOperation.Execute(TreeListNode) Method

Must be implemented to perform an operation on the visited node.

Namespace: DevExpress.XtraTreeList.Nodes.Operations

Assembly: DevExpress.XtraTreeList.v24.2.dll

Declaration

C#

public abstract void Execute(
    TreeListNode node
)

VB.NET

Public MustOverride Sub Execute(
    node As TreeListNode
)

Parameters

Name	Type	Description
node	TreeListNode	A TreeListNode object representing the node against which the operation is to be performed.

Remarks

The Execute method is automatically called for each node visited by the nodes iterator. The currently visited node is transmitted to it as the node parameter. This method is used to implement an operation or the calculation logic performed by the iterator. For instance, the operation may involve calculating the number of nodes that satisfy a specific condition. In this case, the Execute method must check whether the node satisfies the condition and increment a counter, if so.

The Execute method can be performed if the TreeListOperation.CanContinueIteration property returns true.

Most internal operations against nodes are implemented using the nodes iterator. The following examples illustrate how the iterator can be used and in what way the Execute method is implemented.

• Calculating the number of nodes within the XtraTreeList. The Execute method increments a counter.
• Expanding/collapsing all nodes within the XtraTreeList. The Execute method expands or collapsed the currently visited node.
• Printing nodes of the Tree List control. The Execute method prints the currently visited node.

Example

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.

C#

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;
   }
}

VB.NET

Imports DevExpress.XtraTreeList

' declaring the custom operation class
Public Class TreeListExceedLimitOperation
   Inherits TreeListOperation

   Private FieldName As String
   Private UpperLimit As Integer
   Private _result As Integer

   Public Sub New(ByVal FieldName As String, ByVal UpperLimit As Integer)
      Me.FieldName = FieldName
      Me.UpperLimit = UpperLimit
      _result = 0
   End Sub

   ' incrementing the counter if the node's value exceeds the limit
   Public Overrides Sub Execute(ByVal Node As TreeListNode)
      Dim NodeValue As Integer = Convert.ToInt32(Node(FieldName))
      If NodeValue > UpperLimit Then _result += 1
   End Sub

   Public ReadOnly Property Result() As Integer
      Get
         Return _result
      End Get
   End Property
End Class

' ...
' using the created class to calculate the number of nodes
' that have a value greater than 500000 in their Budget field
Private Sub TreeList1_GetCustomSummaryValue(ByVal sender As Object, _
ByVal e As GetCustomSummaryValueEventArgs) Handles TreeList1.GetCustomSummaryValue
   If (e.IsSummaryFooter) Then
      Dim Operation As New TreeListExceedLimitOperation("Budget", 500000)
      TreeList1.NodesIterator.DoOperation(Operation)
      e.CustomValue = Operation.Result
   End If
End Sub