请问为什么sql.executescalar 为 DBNull类型?
jh123 2003-12-09 01:36:36 Dim a As String
Dim b As String
If TextBox1.Text = "" Then
cnKS.Open()
sql.CommandText = "select max(工作组ID) from 工作组 where 工作组ID like '" & Me.ComboBox1.SelectedValue & "'&"
a = CType(sql.ExecuteScalar, String)
cnKS.Close()
以在代码在到: a = CType(sql.ExecuteScalar, String)时,提示:“不能强制把DBNull类型转换为string类型,我查了书了都正确,我真不知道为什么会这样?请各位大大帮忙,谢谢了