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Unable to extract the records the second time I run using the same user id

It only can be called once. where did I gone wrong? The second time it executes, no text appears. The Login and Site.Master are two different partial classes. I am kind of confounded on how to solve this.
Login.aspx
public partial class Login : System.Web.UI.Page
{
SqlDataReader dR;
DatabaseMgmt drObj = new DatabaseMgmt();
protected void Page_Load(object sender, EventArgs e)
{
}
protected void submitButton_Click(object sender, EventArgs e)
{
string strEmail, strPwd;
int intShopperID;
strEmail = txtEmail.Text.ToLower();
strPwd = txtPwd.Text.Trim();
string strSqlCmd = "SELECT ShopperID FROM Shopper WHERE Email ="+ "'" + strEmail + "'" + "AND Passwd ="+ "'"+ strPwd + "'";
dR = drObj.ExecuteSelect(strSqlCmd);
if(dR.Read())
{
intShopperID = Convert.ToInt32(Session["ShopperID"]);
Session["ShopperID"]=intShopperID;
Response.Redirect("Default.aspx");
}
else
{
intShopperID = 0;
lblMsg.Text = "Incorrect email or password";
lblMsg.ForeColor = System.Drawing.Color.Red;
}
dR.Close();
}
}
Site.Master
public partial class Site : System.Web.UI.MasterPage
{
DatabaseMgmt dBObj = new DatabaseMgmt();
protected void Page_Load(object sender, EventArgs e)
{
if (Session["ShopperID"] != null)
{
string strSqlCmd;
strSqlCmd = "SELECT Name FROM Shopper WHERE ShopperID = " + Session["ShopperID"];
lblWelcome.Text = "Welcome Eric";
logoutButton.Visible = true;
loginButton.Visible = false;
regButton.Visible = false;
}
else
{
logoutButton.Visible = false;
loginButton.Visible = true;
regButton.Visible = true;
lblWelcome.Text = "";
}
}
Display Welcome Message
First Run
Second Run
database

I did not see where you are reading the ShopperID from the database. Perhaps that is your issue. ???
To address the Parameterisation issue, I think you should consider something more like this:
public int GetShopperID(System.String strEmail, System.String strPwd) {
int result = 0;
string strSqlCmd = "SELECT ShopperID FROM Shopper WHERE Email = #Email AND Passwd = #Passwd";
using (var cmd = new System.Data.SqlClient.SqlCommand(strSqlCmd, new System.Data.SqlClient.SqlConnection(_databaseConnection))) {
cmd.Parameters.Add("#Email", System.Data.SqlDbType.VarChar, 50);
cmd.Parameters.Add("#Passwd", System.Data.SqlDbType.VarChar, 50);
cmd.Parameter["#Email"].Value = strEmail;
cmd.Parameter["#Passwd"].Value = strPwd;
cmd.Connection.Open();
using (var reader = cmd.ExecuteReader()) {
if (reader.Read()) {
result = Convert.ToInt32(reader["ShopperID"]);
}
}
}
return result;
}

First, it appears you close your connection, however you don't have an explicit open connection (unless you didn't include that line by mistake) which on a postback your query won't produce results since the connection is closed after you run it the first time. Second, confirm you don't have your code in a !Page.IsPostBack, which could also cause it not to appear. Finally you can do all that you are trying to do using one datareader instead of opening up two datareaders with this:
string strEmail = txtEmail.Text.ToLower();
string strPwd = txtPwd.Text.Trim();
string conString = ConfigurationManager.ConnectionStrings["YourConnection"].ConnectionString;
using (SqlConnection con = new SqlConnection(conString))
{
using (SqlCommand cmd = new SqlCommand("SELECT ShopperID, Name FROM Shopper WHERE Email = #Email AND Passwrd = #Passwrd", con))
{
con.Open();
cmd.Parameters.AddWithValue("#Email", strEmail);
cmd.Parameters.AddWithValue("#user_name", strPwd);
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
if (dr.HasRows)
{
if(dr["ShopperID"].ToString() != Session["ShopperID"].ToString())
{
Response.Redirect("~/default.aspx");
}
else if (dr["ShopperID"].ToString() == Session["ShopperID"].ToString())
{
lblWelcome.Text = "Welcome " + dr["Name"].ToString();
}
else
{
lblMsg.Text = "Incorrect email or password";
lblMsg.ForeColor = System.Drawing.Color.Red;
}
}
}
con.Close();
}
}
This also addresses the SQL injection by using Type-Safe SQL Parameters, which was outlined as an issue in other comments.

SQL DataReader: Invalid attempt to read when no data is present to label

I am trying to use a SqlDataReader to run queries on two tables where the 1st column in the Selection table is a foreign key referencing to the Items table, and then display the results in labels, but I keep getting the error:
Invalid attempt to read when no data is present.
Here is my code:
public partial class Read : System.Web.UI.Page
{
SqlConnection conn = new SqlConnection(#"data source = localhost; integrated security = true; database = dev_handin1");
SqlCommand cmd = null;
SqlDataReader rdr = null;
string sqlsel = "SELECT MainItemId FROM Selection";
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
GetInfo();
}
}
private void GetInfo() {
try
{
cmd = new SqlCommand(sqlsel, conn);
conn.Open();
sqlsel = "SELECT * FROM Items WHERE ItemId = MyMainItem";
rdr = cmd.ExecuteReader();
var MyMainItem = rdr[0];
while (rdr.Read())
{
LabelCategory1.Text = rdr[1].ToString();
LabelHeadline1.Text = rdr[2].ToString();
LabelText1.Text = rdr[3].ToString();
LabelJoke1.Text = rdr[4].ToString();
}
}
catch (Exception ex)
{
LabelMessage1.Text = ex.Message;
}
finally
{
rdr.Close();
conn.Close();
}
}
}
}
I'm pretty new at this so please bear with me.

ExecuteReader query with inside of it two ExecuteNonQuery

I've got a problem with some queries from c# to SQL. I need to have a query executeReader and inside of it a if else that allow me to choose between two inserts queries. I'm calling a little external program(with the URL collected into the db) which allows me to choose between 1 and 2, if the 1 is chosen(pass) else(fail). I can't do that because the debug is giving me:
'A Command is yet associated with a DataReader opened, which needs to be closed.'
I don't know what to try anymore.
private void btnSTART_Click(object sender, RoutedEventArgs e)
{
sqliteCon.Open();
if (sqliteCon.State == System.Data.ConnectionState.Open)
{
string path = null;//estrazione1
SqlCommand cmd = new SqlCommand("select nomeI FROM tabL where selection=1", sqliteCon);
SqlDataReader nomeIRdr = null;//estrazione2
//qui
var scriptsToRun = new List<string>();
using (nomeIRdr = cmd.ExecuteReader())
{
while (nomeIRdr.Read())//estrazione4
{
path = nomeIRdr["nomeI"].ToString();//estrazione5
Process MyProc = Process.Start(path);//permette la run del path contenuto nel db
MyProc.WaitForExit();
var exitCode = MyProc.ExitCode;
if (exitCode == 1)
{
scriptsToRun.Add("insert into tabL resItem values 'PASS'");
}
else
{
scriptsToRun.Add("insert into tabL resItem values 'FAIL'");
}
sqliteCon.Close();
}
}
foreach (var script in scriptsToRun)
{
SqlCommand cmd1 = new SqlCommand(script, sqliteCon);
cmd1.ExecuteNonQuery();
}
}
}

Do not share single connection and cram everything into a single routine. Please, keep your code simple.
Create (and Dispose) Connection whenever you query RDBMS
Extract methods
Code:
Process execution and return execution results collection:
// Item1 - path
// Item2 - true in succeed
private List<Tuple<string, bool>> ExecuteResults() {
List<Tuple<string, bool>> result = new List<Tuple<string, bool>>();
using (var con = new SqlConnection(ConnectionStringHere)) {
con.Open();
string sql =
#"select nomeItem
from tabList
where selection = 1";
using (SqlCommand cmd = new SqlCommand(sql, con)) {
using (var reader = cmd.ExecuteReader()) {
while (reader.Read()) {
string path = Convert.ToString(reader[0]);
using (Process process = Process.Start(path)) {
process.WaitForExit();
result.Add(Tuple.Create(path, process.ExitCode == 1));
}
}
}
}
}
return result;
}
Saving results in RDBMS
private void ApplyExecuteResults(IEnumerable<Tuple<string, bool>> results) {
using (var con = new SqlConnection(ConnectionStringHere)) {
con.Open();
string sql =
#"update tabList
set resItem = #prm_resItem
where nomeItem = #prm_nomeItem";
using (SqlCommand cmd = new SqlCommand(sql, con)) {
cmd.Parameters.Add("#prm_nomeItem", SqlDbType.VarChar);
cmd.Parameters.Add("#prm_resItem", SqlDbType.VarChar);
foreach (var item in results) {
cmd.Parameters[0].Value = item.Item1;
cmd.Parameters[1].Value = item.Item2 ? "PASS" : "FAIL";
cmd.ExecuteNonQuery();
}
}
}
}
Finally, combine both routines:
private void btnSTART_Click(object sender, RoutedEventArgs e) {
ApplyExecuteResults(ExecuteResults());
}

Reading Multiple data

private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
{
Ontrip _ontrip = new Ontrip(_FNAME);
string _query2 = "select CContactno from CustomerTbl where CUsername = #USERNAME";
string _query3 = "select Price from TransactionTypeTble T join PendingTransTbl P ON P.TransType = T.TransType ";
string _query4 = "select VehicleDescription from DriverTbl D join VehicleSpecTbl V ON D.VehicleType = V.VehicleType";
SqlConnection _sqlcnn = new SqlConnection("Data Source=MELIODAS;Initial Catalog=WeGo;Integrated Security=True");
_sqlcnn.Open();
try
{
SqlDataReader _reader = null;
SqlCommand _cmd = new SqlCommand("Select CFName+' '+CLName from CustomerTbl where CUsername=#USERNAME", _sqlcnn);
SqlParameter _param = new SqlParameter();
_param.ParameterName = "#USERNAME";
_param.Value = dataGridView1.Rows[e.RowIndex].Cells[1].Value.ToString();
_cmd.Parameters.Add(_param);
_reader = _cmd.ExecuteReader(); //for displaying users name in the label
while (_reader.Read())
{
_ontrip._txtboxUsername.Text = _reader.GetString(0);
}
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
using (SqlCommand _sqlcmd = new SqlCommand(_query2, _sqlcnn))
{
try
{
SqlDataReader _reader = null;
SqlParameter _param = new SqlParameter();
_param.ParameterName = "#USERNAME";
_param.Value = dataGridView1.Rows[e.RowIndex].Cells[1].Value.ToString();
_sqlcmd.Parameters.Add(_param);
_reader = _sqlcmd.ExecuteReader(); //for displaying users name in the label
while (_reader.Read())
{
_ontrip._txtboxContact.Text = _reader.GetString(0);
}
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
Is their a way for me to read the query and display the output, when i run this code their is an error saying that their is already an open data reader associated with the command. I should be displaying multiple data in a textbox

try Call Close when done reading.
_reader.Close();

private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
{
Ontrip _ontrip = new Ontrip(_FNAME);
string _query2 = "select CContactno from CustomerTbl where CUsername = #USERNAME";
string _query3 = "select Price from TransactionTypeTble T join PendingTransTbl P ON P.TransType = T.TransType ";
string _query4 = "select VehicleDescription from DriverTbl D join VehicleSpecTbl V ON D.VehicleType = V.VehicleType";
SqlConnection _sqlcnn = new SqlConnection("Data Source=MELIODAS;Initial Catalog=WeGo;Integrated Security=True;MultipleActiveResultSets=True ");
_sqlcnn.Open();
I added MultipleActiveResultSet or MARS

Reading Data from SQL DataBase Table to generic collection

I wanted to read all data from a table(containg 3 rows) and to add all the data into generic collection.From collection i wana bind to gridview.
The code displayed below works but only last row is displayed 3 times in gridview.Can You help me.Am a beginer
protected void Page_Load(object sender, EventArgs e)
{
List<Student> listid = new List<Student>();
Student stud = new Student();
SqlConnection con = new SqlConnection("........");
string sql = "select * from StudentInfo";
con.Open();
SqlCommand cmd = new SqlCommand(sql, con);
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
stud.Studid = Convert.ToInt32(dr["StudId"]);
stud.StudName = dr["StudName"].ToString();
stud.StudentDept = dr["StudentDept"].ToString();
listid.Add(stud);
}
GridView1.DataSource = listid;
GridView1.DataBind();
}
public class Student
{
private int studid;
public int Studid
{
get { return studid; }
set { studid = value; }
}
private string studName;
public string StudName
{
get { return studName; }
set { studName = value; }
}
private string studentDept;
public string StudentDept
{
get { return studentDept; }
set { studentDept = value; }
}
The output is like this:

You need to instantiate your object inside while loop
Otherwise you will have same data in the collection
So the code should be
protected void Page_Load(object sender, EventArgs e)
{
List<Student> listid = new List<Student>();
SqlConnection con = new SqlConnection("........");
string sql = "select * from StudentInfo";
con.Open();
SqlCommand cmd = new SqlCommand(sql, con);
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
Student stud = new Student();
stud.Studid = Convert.ToInt32(dr["StudId"]);
stud.StudName = dr["StudName"].ToString();
stud.StudentDept = dr["StudentDept"].ToString();
listid.Add(stud);
}
GridView1.DataSource = listid;
GridView1.DataBind();
}
Also it is not a good practice to use while to data reader or directly open connection
You should use using statement.
using(SqlConnection con = new SqlConnection("connection string"))
{
con.Open();
using(SqlCommand cmd = new SqlCommand("SELECT * FROM SomeTable", connection))
{
using (SqlDataReader reader = cmd.ExecuteReader())
{
if (reader != null)
{
while (reader.Read())
{
//do something
}
}
} // reader closed and disposed up here
} // command disposed here
} //connection closed and disposed here

In the DataReader while loop instantiate a new Student for each row in the database table:
while (dr.Read())
{
var stud = new Student();
stud.Studid = Convert.ToInt32(dr["StudId"]);
stud.StudName = dr["StudName"].ToString();
stud.StudentDept = dr["StudentDept"].ToString();
listid.Add(stud);
}