主题：专家看看，为什么并列条件总是写不对？

Dim txt As String = e.Form.Controls("TextBox1").Text
Dim chk As WinForm.CheckBox = e.Form.Controls("CheckBox1")
Dim tbl As Table = Tables("学生档案")

Dim filter As String
If chk.checked Then
    filter = "在校= True"
Else
    filter = "在校= false"
End If
If txt > "" Then
    txt = "'%" & txt & "%'"
    filter =" and 姓名 Like " & txt
End If
tbl.filter = filter

filter变量被后面的语句刷新为"" and 姓名 Like " & txt " ,并不是两个并列条件？