asp.net 登陆问题

Question

问题:登陆提示"ExecuteScalar: CommandText 属性尚未初始化"
login.aspx.vb:
Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim userName As String
Dim userPwd As String
Dim userStyle As String
userName = Request.Form.Get("userName").ToString()
userPwd = Request.Form.Get("userPwd").ToString()
userStyle = Request.Form.Get("selectStyle").ToString
Dim con As New System.Data.SqlClient.SqlConnection("server=localhost;database=data; integrated security=sspi;")
con.Open()
Dim sql As String
' Try
Select Case userStyle
Case "学生"
sql = "select count(*) from stu where name='" + userName + "' and pwd='" + userPwd + "'"""
Case "教师"
sql = "select count(*) from teacher where name='" + userName + "' and pwd='" + userPwd + "'"
Case "管理员"
sql = "select count(*) from admin where name='" + userName + "' and pwd='" + userPwd + "'"
End Select
Dim cmd As New System.Data.SqlClient.SqlCommand(sql, con)
Dim count As Int32
count = Convert.ToInt32(cmd.ExecuteScalar())'提示错误行
If (count > 0) Then
Response.Redirect("main.aspx?userName=" + userName)
Else
Response.Redirect("loginfail.htm")
End If

'Catch ex As Exception
'MsgBox(ex.Message, , "错误信息")
'End Try

End Sub
End Class
我是通过login.html提交到login.aspx的,我初学,不知道哪里错了,哪位高手帮看看啊!

Answer 1

这个再明显不过了，肯定是userStyle里没有select的种类，所以sql文根本就没东西，怎么可能查询得到数据呢。。。你debug下，看看是不是userStyle里根本就没传数据过来。

Answer 2

你这是asp，不是asp.net

Answer 3

我不熟vb在c＃中request不能tostring

Answer 4

我想应该是SqlCommand对象实例化的时候没有初始化T-SQL语句吧。

Answer 5

我是c#的 但是基本能看懂你的登录代码

问题的提示 一定是告诉你命令中的sql没有初始化

对vb不了解,估计是选择语句有错误,没有对sql赋值
c#里面的选择语句在case后还有有break跳出选择,不知道vb有没有类似的,是不是需要跳出选择语句

Answer 6

楼上分析正确,因为userStyle 值不正确,不在case范围,所以sql值为null,SqlCommand(sql, con) 的第一个参数就是CommandText,为null所以没有初始化.

在End Select 前加:

Case Else
Response.Write("<script language=javascript>")
Response.Write("window.alert('用户类型错误! ');")
Response.Write("</script>")
Exit Sub