[求助]从字符串“******”到类型“Boolean”的转换无效。 - 专家坐堂 - Foxtable(狐表) - 新一代数据库软件，完美融合Access、Foxpro、Excel、vb.net之优势，人人都能掌握的快速软件开发工具!

如题，代码如下：

For x As Integer = 2 To 12

For Each r As Row In tb.Rows

cl = sheet(x,0).value

lx = sheet(x,2).value

ys = sheet(x,3).value

If cl <> "" Then

filter = "r(""材料"") = """ & cl & """"

End If

If lx <> "" Then

filter = filter & " AndAlso r(""类型"") = """ & lx & """"

End If

If ys <> "" Then

filter = filter & " AndAlso r(""钥匙"").contains(""" & ys & """)"

End If

filter = filter.TrimStart(" ","A","n","d","l","s","o")

If filter Then

'If r("材料") = cl AndAlso r("类型") = lx AndAlso r("钥匙").contains(ys) Then

For i As Integer = 4 To tb.Cols.Count -1

If r.Isnull(i) = False Then

If sheet(x,i+2).value <> "" Then

sheet(x,i+2).value = sheet(x,i+2).value + r(i)

Else

sheet(x,i+2).value = r(i)

End If

老师，我想根据cl,lx,ys是否是空值来控制if的条件，请问该怎么改？？

主题：[求助]从字符串“******”到类型“Boolean”的转换无效。