下拉列表框的树形展示

#Region "父级任务下拉菜单的绑定"

        ''' <summary>
        '''父级任务的绑定
        ''' </summary>
        ''' <param name="hideascode"></param>
        ''' <remarks></remarks>
        Private Sub DropDownListBind(ByVal hideascode As String)
           '绑定任务下拉列表框(以树开目录展示)
            If ddlTaskName.Items.Count > 0 Then
                ddlTaskName.Items.Clear()
            End If
            Dim lasinfo As New List(Of ProblemInfo)

            lasinfo = control.GetSingleProjectAndTask(Null.ToGuid(ddlProjectName.SelectedValue))
            For i As Integer = 0 To lasinfo.Count - 1
                Dim ascode As String = lasinfo(i).TreeCode
                Dim asname As String = lasinfo(i).tName

                If ascode.Length = 4 Then
                    lasinfo(i).tName = " " + asname
                Else
                    lasinfo(i).tName = GetPointsString(ascode.Length) + "·" + asname
                End If
            Next

            Dim truelasinfo As New List(Of ProblemInfo)

            For Each asif As ProblemInfo In lasinfo
                '如果有子科目
                Dim hideascode As String = "f"
                If asif.TreeCode.IndexOf(hideascode) <> 0 Then
                    truelasinfo.Add(asif)
                End If
            Next
            ddlTaskName.DataSource = truelasinfo
            ddlTaskName.DataTextField = "tName"
            ddlTaskName.DataValueField = "TreeCode"
            ddlTaskName.DataBind()
            ddlTaskName.Items.Insert(0, "--请选择--")
            ddlTaskName.Items(0).Value = "a"
        End Sub
#End Region

#Region "获取缩进字符串"
        '获取缩进符(字符串)
        Private Function GetPointsString(ByVal length As Integer) As String
            Dim str As String
            str = ""

            For i As Integer = 2 To (length / 4) - 1
                str += Server.HtmlDecode("&nbsp;")
            Next
            'str = str.PadLeft((length / 4) - 1, "&nbsp;")
            Return str
        End Function
#End Region