IHierarchicalEnumerable.GetHierarchyData Method (Object)


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Returns a hierarchical data item for the specified enumerated item.

Namespace:   System.Web.UI
Assembly:  System.Web (in System.Web.dll)

Function GetHierarchyData (
	enumeratedItem As Object
) As IHierarchyData


Type: System.Object

The Object for which to return an IHierarchyData.

Return Value

Type: System.Web.UI.IHierarchyData

An IHierarchyData instance that represents the Object passed to the GetHierarchyData method.

Typically, clients that use IHierarchicalEnumerable collections retrieve an IEnumerator object by calling the GetEnumerator method, then iterate through the enumeration and call the GetHierarchyData method on each enumerated item to retrieve an IHierarchyData object.

The following code example demonstrates how an ASP.NET hierarchical data-bound control uses an IHierarchyData object in a recursive data-binding method. The items in an IHierarchicalEnumerable object are enumerated, and for each an IHierarchyData object is retrieved using the GetHierarchyData method. Finally, the HasChildren property is checked to determine whether recursion is necessary. This code example is part of a larger example provided for the HierarchicalDataBoundControl class.

Private Sub RecurseDataBindInternal(ByVal node As TreeNode, _
    ByVal enumerable As IHierarchicalEnumerable, _
    ByVal depth As Integer)

    Dim item As Object
    For Each item In enumerable

        Dim data As IHierarchyData = enumerable.GetHierarchyData(item)

        If Not data Is Nothing Then

            ' Create an object that represents the bound data
            ' to the control.
            Dim newNode As New TreeNode()
            Dim rvnode As New RootViewNode()

            rvnode.Node = newNode
            rvnode.Depth = depth

            ' The dataItem is not just a string, but potentially
            ' an XML node or some other container. 
            ' If DataTextField is set, use it to determine which 
            ' field to render. Otherwise, use the first field.                    
            If DataTextField.Length > 0 Then
                newNode.Text = DataBinder.GetPropertyValue _
                (data, DataTextField, Nothing)
                Dim props As PropertyDescriptorCollection = _

                ' Set the "default" value of the node.
                newNode.Text = String.Empty

                ' Set the true data-bound value of the TextBox,
                ' if possible.
                If props.Count >= 1 Then
                    If Not props(0).GetValue(data) Is Nothing Then
                        newNode.Text = props(0).GetValue(data).ToString()
                    End If
                End If
            End If


            If data.HasChildren Then
                Dim newEnumerable As IHierarchicalEnumerable = _
                If Not (newEnumerable Is Nothing) Then
                    RecurseDataBindInternal(newNode, _
                    newEnumerable, depth + 1)
                End If
            End If

            If MaxDepth < depth Then
                MaxDepth = depth
            End If
        End If
    Next item

End Sub 'RecurseDataBindInternal

.NET Framework
Available since 2.0
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