Question

I ran into a situation where FindControl was returning a control that wasn’t a complete match of the Id I was searching by. There are two controls in the parentcontrol with similar Ids like: “MyControl” and “MyControlAlternate”. When I call FindControl(“MyControl”) the control returned is “MyControlAlternate”. I was wondering if anyone had any explaination why or thoughts as to what might be causing this problem. The way I got around this was implementing my own version of FindControl.

Answer 1

The default behavior of FindControl to use its own naming container. If that doesn’t work it tries to do pattern matching on the name. That would explain why you are getting the wrong control – your naming container is incorrect and the code is making it into the pattern matching phase.

Here is the dissassembly of FindControl from Reflector:

Public Overridable Function FindControl(ByVal id As String) As Control
    Return Me.FindControl(id, 0)
End Function

Protected Overridable Function FindControl(ByVal id As String, ByVal pathOffset As Integer) As Control
    Dim str As String
    Me.EnsureChildControls
    If Not Me.flags.Item(&H80) Then
        Dim namingContainer As Control = Me.NamingContainer
        If (Not namingContainer Is Nothing) Then
            Return namingContainer.FindControl(id, pathOffset)
        End If
        Return Nothing
    End If
    If (Me.HasControls AndAlso (Me._occasionalFields.NamedControls Is Nothing)) Then
        Me.EnsureNamedControlsTable
    End If
    If ((Me._occasionalFields Is Nothing) OrElse (Me._occasionalFields.NamedControls Is Nothing)) Then
        Return Nothing
    End If
    Dim anyOf As Char() = New Char() { "$"c, ":"c }
    Dim num As Integer = id.IndexOfAny(anyOf, pathOffset)
    If (num = -1) Then
        str = id.Substring(pathOffset)
        Return TryCast(Me._occasionalFields.NamedControls.Item(str),Control)
    End If
    str = id.Substring(pathOffset, (num - pathOffset))
    Dim control2 As Control = TryCast(Me._occasionalFields.NamedControls.Item(str),Control)
    If (control2 Is Nothing) Then
        Return Nothing
    End If
    Return control2.FindControl(id, (num + 1))
End Function

Clearly what is happening in your example is that you are not specifying the correct naming container. However, without providing a code example I cannot be more specific than this.