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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.

C# How to Update/Change the specific letter/number of a string in database

I ask these question coz i really don't know how i'm gonna do that and is it possible to do that?
What i want is to update/change here for example STA-100418-100 in database values, update/change the 100 based on the user input, like 50 it will be STA-100418-50.
Here's the provided image to be more precise
As you can see on the image, there's a red line, if user update the quantity as 60, In Codeitem STA-100418-100 should be STA-100418-60
I really have no idea on how to do that. I hope someone would be able to help me
here's my code for updating the quantity
private void btn_ok_Click(object sender, EventArgs e)
{
using (var con = SQLConnection.GetConnection())
{
using (var selects = new SqlCommand("Update Product_Details set quantity = quantity - #Quantity where ProductID= #ProductID", con))
{
selects.Parameters.Add("#ProductID", SqlDbType.VarChar).Value = _view.txt_productid.Text;
selects.Parameters.Add("#Quantity", SqlDbType.Int).Value = Quantity;
selects.ExecuteNonQuery();
}
}
}
Here's the code to get that format in codeitems
string date = DateTime.Now.ToString("MMMM-dd-yyyy");
string shortdate = DateTime.Now.ToString("-MMddy-");
private void Quantity_TextChanged(object sender, EventArgs e)
{
Code.Text = Supplier.Text.Substring(0, 3) + shortdate + Quantity.Text;
}

Here's what I use to update SQL-Server
public static DataTable GetSqlTable(string sqlSelect)
{
string conStr = ConfigurationManager.ConnectionStrings["connString"].ConnectionString;
DataTable table = new DataTable();
SqlConnection connection = new SqlConnection(conStr);
try
{
connection.Open();
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
if (connection.State != ConnectionState.Open)
{
return table;
}
SqlCommand cmd = new SqlCommand(sqlSelect, connection);
SqlDataAdapter adapter = new SqlDataAdapter(cmd);
try
{
adapter.Fill(table);
}
catch(Exception ex)
{
MessageBox.Show(ex.ToString());
throw;
}
connection.Close();
connection.Dispose();
return table;
}
public static void GetSqlNonQuery(string sqlSelect)
{
string newObject = string.Empty;
string strConn = ConfigurationManager.ConnectionStrings["connString"].ConnectionString;
SqlConnection connection = new SqlConnection(strConn);
connection.Open();
if (connection.State != ConnectionState.Open)
{
return;
}
try
{
SqlCommand cmd = new SqlCommand(sqlSelect, connection);
cmd.ExecuteNonQuery();
connection.Close();
connection.Dispose();
}
catch (Exception ex)
{
string x = ex.Message + ex.StackTrace;
throw;
}
}
Here's how to use it
DataTable dt = GetSqlTable("select Quantity from product where CodeItem = 'STA-100418-100'");
string strQuantity = dt.Rows[0]["Quantity"].ToString();
GetSqlNonQuery(string.Format("UPDATE product SET CodeItem = '{0}' WHERE = 'STA-100418-100'", strQuantity));

User will input everytime in the Quantity textbox, the textchanged event of Quantity will be hit and you will get new value everytime with the same date but with different quantity. So you can use the Code.Text to update the CodeDateTime value or you can use a global variable instead of Code.Text and use it to update the column.
string date = DateTime.Now.ToString("MMMM-dd-yyyy");
string shortdate = DateTime.Now.ToString("-MMddy-");
private void Quantity_TextChanged(object sender, EventArgs e)
{
Code.Text = Supplier.Text.Substring(0, 3) + shortdate + Quantity.Text;
}
using (var con = SQLConnection.GetConnection())
{
using (var selects = new SqlCommand("Update Product_Details set quantity = quantity - #Quantity, CodeItem = #Code where ProductID= #ProductID", con))
{
selects.Parameters.Add("#ProductID", SqlDbType.VarChar).Value = _view.txt_productid.Text;
selects.Parameters.Add("#Quantity", SqlDbType.Int).Value = Quantity;
selects.Parameters.Add("#Code", Code.Text);
}
}

as I understand it you need MSSQL String Functions
SELECT rtrim(left(Codeitem,charindex('-', Codeitem))) + ltrim(str(Quantity)) FROM ...
For detailed information

Using MySql, Substring the code item and then concatenate the quantity.
UPDATE Product_Details SET quantity = #quantity,CodeIem = CONCAT(SUBSTR(#code,1,11),#quantity) WHERE ProductID= #ProductID

SQLDataReader bugging while using .Nest() or .Read()

I'm retrieving some information from an MSSQL via SQLDataReader, but while debugging it I notice in some cases the reader clears the result view with the error "Enumeration yielded no results" see the screenshot Before Running passing Read(),
After passing read()
this is my code,the error happens on getActiveUsers() method.
getDatabases() works just fine. could someone help me? cheers
public partial class automation : System.Web.UI.Page
{
SqlConnection con;
static List<ActiveUsers> activeUsers = new List<ActiveUsers>();
protected void Page_Load(object sender, EventArgs e)
{
ASPxGridView1.DataSource = activeUsers.ToList();
}
public List<ActiveUsers> getDatabases()
{
//passing query
string SqlQuery = "SELECT [WorkspaceName],[MaConfig_Customers].Name FROM [MaConfig_CustomerDatabases] INNER JOIN [MaConfig_Customers] ON [MaConfig_CustomerDatabases].CustomerId = [MaConfig_Customers].CustomerId where [MaConfig_Customers].Status = 0";
//creating connection
string sqlconn = ConfigurationManager.ConnectionStrings["MaxLiveConnectionString"].ConnectionString;
con = new System.Data.SqlClient.SqlConnection(sqlconn);
var cmd = new SqlCommand(SqlQuery, con);
con.Open();
SqlDataReader reader = cmd.ExecuteReader();
List<ActiveUsers> results = new List<ActiveUsers>();
if (reader.Read())
{
while (reader.Read())
{
ActiveUsers company = new ActiveUsers();
company.DatabaseName = String.Format("{0}", reader["WorkspaceName"]);
company.ClientName = String.Format("{0}", reader["Name"]);
results.Add(company);
}
}
con.Close();
return results;
}
public void getActiveUsers()
{
activeUsers.Clear();
List<ActiveUsers> Databases= getDatabases();
SqlConnection conn = new SqlConnection();
string SqlQuery = "select [disabled], [ADMN_Users1].[Record_Id] ,[ADMN_Users].[User_Id] from admn_Users1 inner join [ADMN_Users] on [ADMN_Users1].[record_Id] = [ADMN_Users].[Record_Id] Where [disabled] & 0x2 = 0 ";
for (int i = 0;i < Databases.Count;i++)
{
conn.ConnectionString =
"Data Source=MAXSQLCLUS01;" +
"Initial Catalog=" + Databases[i].ToString()+";"+
"User id=sa;" +
"Password=Max1m1zer;";
var cmd = new SqlCommand(SqlQuery, conn);
conn.Open();
SqlDataReader reader = cmd.ExecuteReader();
int NumberOfUsersCounter = 0 ;
//TODO Select Enabled users
if (reader.Read())
{
while (reader.Read())
{
string user = String.Format("{0}", reader["User_Id"]);
//logic to remove system users
if (user.Equals("master", StringComparison.CurrentCultureIgnoreCase))
{
}
else
if (user.Equals("emailuser", StringComparison.CurrentCultureIgnoreCase))
{
}
else
if (user.Equals("webuser", StringComparison.CurrentCultureIgnoreCase))
{
}
else
{
NumberOfUsersCounter++;
}
}
ActiveUsers newEntry = new ActiveUsers();
newEntry.NumberActiveUsers = NumberOfUsersCounter.ToString();
newEntry.DatabaseName = Databases[i].DatabaseName.ToString();
newEntry.ClientName = Databases[i].ClientName.ToString();
activeUsers.Add(newEntry);
}
conn.Close();
//Add to ActiveUsers list
}
ASPxGridView1.AutoGenerateColumns = true;
ASPxGridView1.DataSource = activeUsers.ToList();
ASPxGridView1.DataBind();
}
protected void ASPxButton1_Click(object sender, EventArgs e)
{
getActiveUsers();
}
protected void btnExportExcel_Click(object sender, EventArgs e)
{
ASPxGridView1.DataBind();
ASPxGridViewExporter1.Landscape = true;
ASPxGridViewExporter1.FileName = "User Count Report";
ASPxGridViewExporter1.WriteXlsToResponse();
}
}
}

if (reader.Read())
{
while (reader.Read())
{
ActiveUsers company = new ActiveUsers();
company.DatabaseName = String.Format("{0}", reader["WorkspaceName"]);
company.ClientName = String.Format("{0}", reader["Name"]);
results.Add(company);
}
}
use this
if (reader.HasRows)
{
while (reader.Read())
{
ActiveUsers company = new ActiveUsers();
company.DatabaseName = String.Format("{0}", reader["WorkspaceName"]);
company.ClientName = String.Format("{0}", reader["Name"]);
results.Add(company);
}
}
your if Condition is wrong
if(reader.Read()) ==> is Wrong
Read() is not return boolean Value
use HasRows to check rows in SQLDataReader

You are skipping the first result. if (reader.Read()) { while(reader.Read()) {.... Remove the enclosing if, all it does is see if there is a row and retrieve it but then you do not read it, instead you do it again in the if so the first result is always discarded.
public List<ActiveUsers> getDatabases()
{
//passing query
string SqlQuery = "SELECT [WorkspaceName],[MaConfig_Customers].Name FROM [MaConfig_CustomerDatabases] INNER JOIN [MaConfig_Customers] ON [MaConfig_CustomerDatabases].CustomerId = [MaConfig_Customers].CustomerId where [MaConfig_Customers].Status = 0";
//creating connection
string sqlconn = ConfigurationManager.ConnectionStrings["MaxLiveConnectionString"].ConnectionString;
using(con = new System.Data.SqlClient.SqlConnection(sqlconn))
using(var cmd = new SqlCommand(SqlQuery, con))
{
con.Open();
using(SqlDataReader reader = cmd.ExecuteReader())
{
List<ActiveUsers> results = new List<ActiveUsers>();
while (reader.Read())
{
ActiveUsers company = new ActiveUsers();
company.DatabaseName = reader.GetString(0);
company.ClientName = reader.GetString(1);
results.Add(company);
}
}
}
return results;
}
Side notes:
company.DatabaseName = String.Format("{0}", reader["WorkspaceName"]) would be better written as company.DatabaseName = reader.GetString(0). The same goes for the next line. No need to use string.Format and you are specifying the columns and order in the query so use the ordinal index so get the native value.
I would recommend you wrap the SqlConnection and SqlDataReader in using blocks to ensure they are closed/disposed after use even in the event of an exception.

Image.MemoryStream : Parameter not valid

When I'm trying to retrieve my image by combo box there show the massage . Parameter not valid
I was try many way but problem is same ..
Every time I run the code below, I get same massage.
private void cBoxSearch_SelectedIndexChanged(object sender, EventArgs e)
{
try
{
con = ConnectionController.GetInstance().GetConnection();
con.Open();
com = new SQLiteCommand("SELECT * FROM Stock WHERE ProductName = '" + cBoxSearch.Text + "' ", con);
myReader = com.ExecuteReader();
product prod = new product();
while (myReader.Read())
{
prod.proid = myReader[0].ToString();
prod.prodname = myReader[1].ToString();
prod.proMdl = myReader[2].ToString();
prod.serialN = myReader[3].ToString();
prod.byibgPr = myReader[4].ToString();
prod.sellPr = myReader[5].ToString();
prod.quantity = myReader[6].ToString();
tbxProductID.Text = prod.proid;
tbxName.Text =prod.prodname;
tbxModel.Text = prod.proMdl;
tbxserial.Text = prod.serialN;
tbxbyingprice.Text = prod.byibgPr;
tbxSellingprice.Text = prod.sellPr;
tbxQuantity.Text = prod.quantity;
prod.imgg = (byte[])(myReader[7] );
if (prod.imgg == null)
{
pBX.Image = null;
}
else
{
MemoryStream mstrm = new MemoryStream(prod.imgg);
Bitmap bmp = new Bitmap(mstrm);
}
}
con.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
com.Cancel();
con.Close();
}

Try to consult this question:
convert binary to bitmap using memory stream
Also, it might depend on DBType of the 8th column of the query.

Retrieve database values to textboxes whenever listbox selected index changed

so I just want to view the values from my database to some textboxes in my project whenever the selected index of listbox changes
I have these code but whenever I click an item on my listbox, none of the textboxes displays a data or anything
protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e)
{
if (IsPostBack)
{
try
{
SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionStringHRMS"].ConnectionString);
conn.Open();
string selectone = "SELECT * FROM Applicant WHERE ApplicationNo = '" + ListBox1.SelectedValue.ToString() + "'";
SqlCommand cmd = new SqlCommand(selectone, conn);
SqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
asln.Text = reader["LastName"].ToString();
asfn.Text = reader["FirstName"].ToString();
asmn.Text = reader["MiddleName"].ToString();
ashea.Text = reader["HEA"].ToString();
astitle.Text = reader["Title"].ToString();
aspos.Text = reader["Position"].ToString();
asaddress.Text = reader["Address"].ToString();
asbday.Text = reader["Birthday"].ToString();
asgender.Text = reader["Gender"].ToString();
asage.Text = reader["Age"].ToString();
asht.Text = reader["Height"].ToString();
aswt.Text = reader["Weight"].ToString();
asemail.Text = reader["Email"].ToString();
ascontact.Text = reader["ContactNumber"].ToString();
}
reader.Close();
conn.Close();
}
catch (Exception ex)
{
Response.Write(ex);
}
}
}