主题：[求助]值不能为空应在哪里增加判断

要判读字符串是不是空格字符串，如

    For Each yjdnr As String In yjdnrs
        If yjdnr > "" AndAlso yjdnr <> "空白" Then
            nrtrv.Nodes.Add(yjdnr)
            If tbjdnrs.Contains(yjdnr) Then
                If sxpd = True Then
                    nrtrv.Nodes(yjdnr).Checked = True
                End If
            End If
        End If
    Next