要单独判断 【所有】 节点。

 If e.Node.Text = "所有" Then

 else

 End If

或者这样

Dim nms As String() = {"单位名称","考试名称","年级代码","班级"} \'指定生成目录树的各列
Dim qts As String() = {"\'","\'","\'","\'"} \'指定将各列的值括起来的符号,这里都是字符型,所以都是单引号
Dim trv As WinForm.TreeView = e.Sender
Dim flt As String = ""
If e.node.text = "所有勾选" Then
    flt = "1=1"
Else
    Dim nd As WinForm.TreeNode
    For Each nd In e.node.allNodes \'清除子节点的选中标记
        nd.Checked = False
    Next
    nd = e.Node.ParentNode
    Do While nd IsNot Nothing \'清除父节点的选中标记
        nd.Checked = False
        nd = nd.ParentNode
    Loop
    For Each nd In trv.AllNodes
        If nd.Checked andalso nd.text <> "所有勾选" Then
            Dim rts() As String = nd.FullPath.Split("\\")
            Dim val As String = ""
            For i As Integer = 0 To rts.length - 1
                If val > "" Then
                    val = val & " And "
                End If
                val = val & nms(i) & " = " & qts(i) & rts(i) & qts(i)
            Next
            If flt > "" Then
                flt = flt & " Or (" & val & ")"
            Else
                flt = val
            End If
        End If
    Next
End If
Dim schoolName As String = user.group
DataTables("成绩").LoadFilter = "(" & Flt & ") and [_Locked] = 0 And 单位名称 = \'" & schoolname & "\'"
DataTables("成绩").Load()
Tables("成绩").sort = "考试名称,年级代码,考号"