这是一段vb.net代码，想实现登录的功能，调试没错，但是一运行就会出错，大家帮我看看啊！！

[wlpshhh]

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click


Dim myconn As New clssql
Dim username As String = ""
Dim userpassword As String = ""
Dim myda As SqlDataAdapter = New SqlDataAdapter("select * from 用户信息表 where u_name='" & username & "'and u_password ='" & userpassword & "' ", myconn.sqlperate)
Dim myds As New DataSet
Dim mytable As New DataTable


myconn.sqlperate.Open()
myda.Fill(myds)
myda.Fill(mytable)

myconn.sqlperate.Close()

Dim i As Integer
For i = 0 To mytable.Rows.Count
username = mytable.Rows.Item(i).ToString
If TextBox1.Text <> username Then '判断用户是否存在

Continue For
Else
Me.Response.Redirect("index.aspx")

End If

Next
End Sub
这是一段vb.net代码，想实现登录的功能，调试没错，但是一运行就会出错，大家帮我看看啊！！

[足球中国]

For i = 0 To mytable.Rows.Count -1''''''''''''''''''''''''''''''''
username = mytable.Rows.Item(i).ToString
If TextBox1.Text <> username Then '判断用户是否存在

Continue For
Else
Me.Response.Redirect("index.aspx")

End If

Next

[caofusheng]

For i = 0 To mytable.Rows.Count =====》For i =0 To mytable.Rows.Count-1