Dim uName As String = e.Form.Controls("txtName").Value
Dim pwd As String = e.Form.Controls("txtpwd").value
Dim cmd As New SQLCommand
Dim dt As DataTable
Dim dr As DataRow
cmd.C
If uName = "" Then
    Messagebox.show("请输入用户名!","提示",MessageBoxButtons.OK,MessageBoxIcon.Warning)
    Return
Else If pwd = ""
    Messagebox.show("密码不能为空!","提示",MessageBoxButtons.OK,MessageBoxIcon.Warning)
    Return
End If
cmd.CommandText = "Select * From {userInfo}  Where [userID] = \'" & uName.trim() & "\'"
dt = cmd.ExecuteReader

If dt Is Nothing Then  数据查询出来结果，但是却不往下面执行
    dr = dt.DataRows(1)
    If e.Form.Controls("txtpwd").Value = dr("userPwd") Then
        _UserName = uName
        _UserGroup = dr("userDES")
        MessageBox.Show("登录成功!" & 1,"提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
    Else
        Messagebox.show("密码错误!" ,"提示",MessageBoxButtons.OK,MessageBoxIcon.Warning)
    End If
Else
    MessageBox.Show("用户名或密码错误,请重新输入!","提示" ,MessageBoxButtons.OK,MessageBoxIcon.Warning)     每次执行的是这句
   \' e.Form.Controls("txtpwd").value = ""
End If

开始做测试的时候，执行还正确，可是后来在项目打开后，就不能正常使用了，这是怎么回事！

哦~谢谢！我都没留意呢，劳烦了！