Question

I’m trying to create a function that searches up a WebControl’s parent-child relationship (basically the opposite of WebControl.FindControl(id as String), but looking for a specific WebControl type).

Example:
I have a user control in an ItemTemplate for a GridViewRow. I’m trying to reference the GridViewRow from the user control. The user control may or may not be inside a div or other types of controls, so I don’t know exactly how many parent’s up to look (i.e. I can’t just use userControl.Parent.Parent). I need a function that will find the first GridViewRow that it finds on the way up the parent-child hierarchy.

Thus the need for this function. Unless there’s a better way to do this?
Anyway, I want to the function I’m creating to be fairly generic, so that different WebControl types (i.e. GridViewRow, Panel, etc.) can be specified depending on what I’m looking for. Here’s the code I’ve written:

Public Function FindParentControlByType(ByRef childControl As WebControl, ByVal parentControlType As WebControl.Type, Optional ByRef levelsUp As Integer = Nothing) As WebControl
    Dim parentControl As WebControl = childControl
    Dim levelCount = 1
    Do While Not parentControl.GetType = parentControlType
        If Not levelsUp = Nothing AndAlso levelCount = levelsUp Then
            parentControl = Nothing
            Exit Do
        End If
        levelCount += 1
        parentControl = parentControl.Parent
    Loop
    parentControl.FindControl(
    Return parentControl
End Function

I know the “ByVal parentControlType as WebControl.Type” in the function definition won’t work — that’s what I’m looking for.

I’m sure there’s a better way to do this, so please feel free to make me look simple by point it out!

Thanks Guys!

Answer 1

you should be able to do this easily using recursion. here’s an example to get you started or possibly solve your problem.

not exactly that great on VB syntax anymore, but i’m sure you could run this through a converter (like converter.telerik.com)

C# code

public T FindParentControl<T>(
    ref WebControl child, 
    int currentLevel, 
    int maxLevels)
    where T : WebControl
{
    if (child.Parent == null || currentLevel > maxLevels)
        return null;

    if (child.Parent is T)
        return child.Parent as T;
    else 
        return FindParentControl<T>(
            child.Parent, 
            currentLevel + 1, 
            maxLevels);
}

VB.NET Code (by converter.telerik.com)

Public Function FindParentControl(Of T As WebControl)(
    ByRef child As WebControl,
    currentLevel As Integer, 
    maxLevels As Integer) As T

    If child.Parent = Nothing OrElse currentLevel > maxLevels Then
        Return Nothing
    End If

    If TypeOf child.Parent Is T Then
        Return TryCast(child.Parent, T)
    Else
        Return FindParentControl(Of T)(child.Parent, currentLevel + 1, maxLevels)
    End If
End Function