System.InvalidCastException：无法弄清楚原因究竟如何

Question

我更改了我的存储过程以指示经过身份验证的用户是教师还是学生还是管理员..堆栈跟踪：

[InvalidCastException: Specified cast is not valid.]
   myLogin.submitID_Click1(Object sender, EventArgs e) +191
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +118
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +112
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5563

这是存储过程：

ALTER PROCEDURE dbo.StoredProcedure1
    /*
    (
    @parameter1 int = 5,
    @parameter2 datatype OUTPUT
    )
    */
    (

    @Email nvarchar(50),
    @pass nvarchar(50),
    @outres int = null OUTPUT,
    @outres1 int = null OUTPUT,
    @outres2 int = null OUTPUT,
    @outres3 int = null OUTPUT,
    @kind int = null OUTPUT
    )
AS
    /* SET NOCOUNT ON */
     DECLARE @UserId INT



    set @outres1 =  (SELECT count(*) FROM [dbo].Admins 
WHERE admin_Email=@Email AND admin_Pass=@pass)
if (@outres1=1)
 begin
 set @kind=1
 set @outres=@outres1
 SELECT @UserId = adminID
      FROM [dbo].Admins WHERE admin_Email=@Email AND admin_Pass=@pass

      set @outres1= @UserId
    RETURN @outres 
    end

set @outres2= (SELECT count(*) FROM [dbo].Instructors 
WHERE inst_Email=@Email AND inst_Pass=@pass)
if (@outres2=1)
 begin
 set @kind=2
 set @outres=@outres2
 SELECT @UserId = instructorID
      FROM [dbo].Instructors 
WHERE inst_Email=@Email AND inst_Pass=@pass
  set @outres2= @UserId
 RETURN @outres 
    end
set @outres3= (SELECT count(*) FROM [dbo].Students 
WHERE stu_Email=@Email AND stu_Pass=@pass)
if (@outres3=1)
begin
set @kind=3
set @outres= @outres3
SELECT @UserId = studentID
      FROM [dbo].Students 
WHERE stu_Email=@Email AND stu_Pass=@pass
 set @outres3= @UserId
RETURN @outres 
end 
else
begin
set @outres=@outres3
set @outres1=0
set @outres2=0
set @outres3=0
RETURN @outres
end

当学生登录时很好，Response.Redirect会转到指定的页面而不是教师。我尝试将教师重定向到学生页面，它也没有用，现在没有人可以登录。这是代码隐藏的代码：

public int Validate_Login(String _Email, String _Password)
{
    string lbl;
    string connstr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
    SqlConnection con = new SqlConnection(connstr);
    SqlCommand cmdselect = new SqlCommand();
    cmdselect.CommandType = CommandType.StoredProcedure;
    cmdselect.CommandText = "[dbo].[StoredProcedure1]";
    cmdselect.Parameters.Add("@Email", SqlDbType.NVarChar, 50).Value = _Email;
    cmdselect.Parameters.Add("@pass", SqlDbType.NVarChar, 50).Value = _Password;
    cmdselect.Parameters.Add("@outres", SqlDbType.Int, 4);
    cmdselect.Parameters.Add("@outres1", SqlDbType.Int, 4);
    cmdselect.Parameters.Add("@outres2", SqlDbType.Int, 4);
    cmdselect.Parameters.Add("@outres3", SqlDbType.Int, 4);
    cmdselect.Parameters.Add("@kind", SqlDbType.Int, 4);
    cmdselect.Parameters["@outres"].Direction = ParameterDirection.Output;
    cmdselect.Parameters["@outres1"].Direction = ParameterDirection.Output;
    cmdselect.Parameters["@outres2"].Direction = ParameterDirection.Output;
    cmdselect.Parameters["@outres3"].Direction = ParameterDirection.Output;
    cmdselect.Parameters["@kind"].Direction = ParameterDirection.Output;
    cmdselect.Connection = con;
    int Results = 0;
    try
    {
        con.Open();
        // SqlDataReader rd = cmdselect.ExecuteReader();
        cmdselect.UpdatedRowSource = UpdateRowSource.OutputParameters;
        cmdselect.ExecuteNonQuery();
        //cmdselect.ExecuteScalar();
        /* if (rd.HasRows)
          {
              rd.Read();
             // lblinfo.Text = "You are Authorized.";
              FormsAuthentication.RedirectFromLoginPage(ETB.Text, true);
              Response.Redirect("Welcome.aspx");
          }
          else
          {
              lblmsg.Text = "Invalid username or password.";
          }*/
        Results = (int)cmdselect.Parameters["@outres"].Value;
        int res1 = (int)cmdselect.Parameters["@outres1"].Value;
        int res2 = (int)cmdselect.Parameters["@outres2"].Value;
        int res3 = (int)cmdselect.Parameters["@outres3"].Value;
        int knd = (int)cmdselect.Parameters["@kind"].Value;
        if (Results == 0)
        {
            Session["userID"] = null;
        }
        else
        {
            if (res1 != 0)
            {
                Session["userID"] = res1.ToString();
            }
            else if (res2 != 0)
            {
                Session["userID"] = res2.ToString();
                Session["userKind"] = knd.ToString();
            }
            else
            {
                Session["userID"] = res3.ToString();
                Session["userKind"] = knd.ToString();
            }
        }
    }
    catch (SqlException ex)
    {
        lbl = ex.Message;
    }
    finally
    {
        cmdselect.Dispose();
        if (con != null)
        {
            con.Close();
        }
    }

    return Results;
}

protected void submitID_Click1(object sender, EventArgs e)
{
    int Results = 0;
    DataBind();
    Results = Validate_Login(ETB.Text.Trim(), pwdTB.Text.Trim());
    if (Results == 1)
    {
        Session["user"] = TextBox1.Text;
        int ukind = (int)Session["userKind"];
        if (ukind == 3)
        {
            Response.Redirect("Welcome.aspx#profile");
        }

        if (ukind == 2)
        {
            Response.Redirect("welcomeNew.aspx");
        // Response.Redirect("Welcome.aspx#profile");
        }
        else
        {
            Response.Redirect("Default.aspx");
        // Response.Redirect("welcomeInstructor.aspx");
        }
    /*  if (Page.PreviousPage == Session["prevPage"])
        {
            Response.Redirect("courses.aspx");
        }*/
    }
    else
    {
        lblmsg.Text = Results + " Email and Password don't Match !";
        lblmsg.ForeColor = System.Drawing.Color.Orange;
    }
// }
/*   lblmsg.Text = "Please make sure that the username and the password is Correct";
       lblmsg.ForeColor = System.Drawing.Color.Red;*/
}

请帮忙......