c# - 读取器关闭错误时调用读取的尝试无效

Question

我正在为员工创建一个新的登录页面并遇到错误

    mDB.Open();
    SqlCommand cmd;
    SqlDataReader rdr;
    String strSql1 = "SELECT * FROM Employee ";
    cmd = new SqlCommand(strSql1, mDB);
    rdr = cmd.ExecuteReader();

    while (rdr.Read() == true)
    {
        if (txtUsername.Text == (string)rdr["eUserName"] &&
            txtPassword.Text == (string)rdr["ePassword"])
         {
            Session["sFlag"] = "T"; // sFlag = "T" means user has logged in
            Session["sFirstName"] = rdr["eFirstName"];
            Session["sLastName"] = rdr["eLastName"];
            Session["sUsername"] = rdr["eUserName"];
            btnLogout.Visible = true;
            btnLogin.Visible = false;
            mDB.Close();

        } //end of if
    } //end of while loop
 // userid and password not matched, hence login unsuccessful
    Session["sFlag"] = "F";
    Session["sName"] = "";
    Session["sUsername"] = "";
    lblMessage.Text = "Username and password does not match- please try again.  ";
    mDB.Close();
}
protected void btnLogout_Click(object sender, EventArgs e)
{
    btnLogout.Visible = false;
    Session["sFlag"] = "L"; // L for logout
    Session["sFirstName"] = "";
    Session["sUsername"] = "";

}

它适用于我的其他客户登录页面。请帮助？我对此很陌生。非常感谢大家!

Answer 1

您正在关闭读取循环内的连接(使用 mDB.Close();)。这根本不是什么好事。要解决这个问题，请将关闭调用移至循环结束后完成:

while (rdr.Read() == true)
{
    if (txtUsername.Text == (string)rdr["eUserName"] &&
        txtPassword.Text == (string)rdr["ePassword"])
    {
        Session["sFlag"] = "T"; // sFlag = "T" means user has logged in
        Session["sFirstName"] = rdr["eFirstName"];
        Session["sLastName"] = rdr["eLastName"];
        Session["sUsername"] = rdr["eUserName"];
        btnLogout.Visible = true;
        btnLogin.Visible = false;


    } //end of if
} //end of while loop
mDB.Close();