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Check SQL for Book_Availability before issuing one (BookAvailability-1)

If I put "if, foreach, and else statement under comment //", the program works and Reduces book count by 1 from SQL database. But I want to check IF there is at least 1 available book to give. This code keeps showing me the message in "else" statement if I leave it like this. Help is needed fast, it's my final project, that is needed to be done before 23.07. :(
int book_qty = 0;
SqlCommand cmd2 = connection.CreateCommand();
cmd2.CommandType = CommandType.Text;
cmd2.CommandText = "SELECT * FROM Book_list WHERE BookName = '" + TextBoxBookName + "'";
cmd2.ExecuteNonQuery();
DataTable dt2 = new DataTable();
SqlDataAdapter da2 = new SqlDataAdapter(cmd2);
da2.Fill(dt2);
foreach (DataRow dr2 in dt2.Rows)
{
book_qty = Convert.ToInt32(dr2["book_qty"].ToString());
}
if (book_qty > 0)
{
SqlCommand cmd = connection.CreateCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = "INSERT INTO Issue_book VALUES(" + TextBoxSearchMembers.Text + ",'" + TextBoxMemberName.Text + "','" + TextBoxMemberContact.Text + "','" + TextBoxMemberEmail.Text + "','" + TextBoxBookName.Text + "', '" + DateTimePicker1.Text + "')";
cmd.ExecuteNonQuery();
SqlCommand cmd1 = connection.CreateCommand();
cmd1.CommandType = CommandType.Text;
cmd1.CommandText = "UPDATE Book_list SET BookAvailability = BookAvailability-1 WHERE BookName ='" + TextBoxBookName.Text + "'";
cmd1.ExecuteNonQuery();
MessageBox.Show("successful issue");
this.Close();
else
{
MessageBox.Show("Book not available");
}

You are only checking book_qty from the last row in your result set instead of BookAvailability for all rows. You probably want to do something like:
SqlCommand cmd2 = connection.CreateCommand();
cmd2.CommandType = CommandType.Text;
cmd2.CommandText = "SELECT BookAvailability FROM Book_list WHERE BookName = '" + TextBoxBookName + "'";
var result = cmd2.ExecuteScalar();
book_qty = Convert.ToInt32(result);
You need to make sure that there is only one book with the given bookname available.
In that case just correcting this one line in your code would help as well:
book_qty = Convert.ToInt32(dr2["book_qty"].ToString());
to
book_qty = Convert.ToInt32(dr2["BookAvailability"].ToString());
Otherwise you'd need to query SUM(BookAvailability), but the following code would decrease the amount of books for multiple books at once, that wouldn't be good.

Untested code. I don't have your database. Comments and explanation in line.
private void OPCode()
{
try
{
//keep your connections close to the vest (local)
using (SqlConnection connection = new SqlConnection())
//a using block ensures that your objects are closed and disposed
//even if there is an error
{
using (SqlCommand cmd2 = new SqlCommand("SELECT BookAvailability FROM Book_list WHERE BookName = #BookName", connection))
{
//Always use parameters to protect from sql injection
//Also it is easier than fooling with the single quotes etc.
//If you are referring to a TextBox you need to provide what property is
//being accessed. I am not in a WPF right now and not sure if .Text
//is correct; may be .Content
//You need to check your database for correct data type and field size
cmd2.Parameters.Add("#BookName", SqlDbType.VarChar, 100).Value = TextBoxBookName.Text;
//A select statement is not a non-query
//You don't appear to be using the data table or data adapter
//so dump them extra objects just slow things dowm
connection.Open();
//Comment out the next 2 lines and replaced with
//Edit Update
//var returnVal = cmd2.ExecuteScalar() ?? 0;
//if ((int)returnVal > 0)
//*************************************************************
//Edit Update
//*************************************************************
//in case the query returns a null, normally an integer cannot
//hold the value of null so we use nullable types
// the (int?) casts the result of the query to Nullable of int
Nullable<int> returnVal = (int?)cmd2.ExecuteScalar();
//now we can use the .GetValueOrDefault to return the value
//if it is not null of the default value of the int (Which is 0)
int bookCount = returnVal.GetValueOrDefault();
//at this point bookCount should be a real int - no cast necessary
if (bookCount > 0)
//**************************************************************
//End Edit Update
//**************************************************************
{
using (SqlCommand cmd = new SqlCommand("INSERT INTO issue_book VALUES(#SearchMembers etc", connection))
{
//set up the parameters for this command just like the sample above
cmd.Parameters.Add("#SearchMembers", SqlDbType.VarChar, 100).Value = TextBoxSearchMembers.Text;
cmd.ExecuteNonQuery();
}
using (SqlCommand cmd1 = new SqlCommand("UPDATE Book_list SET BookAvailability = BookAvailability-1 WHERE BookName = #BoxBookName;", connection))
{
cmd1.Parameters.Add("#BoxBookName", SqlDbType.VarChar, 100);
cmd1.ExecuteNonQuery();
}
MessageBox.Show("success");
this.Close();
}
else
{
MessageBox.Show("Book not available");
}
}
}
}
catch (Exception exc)
{
MessageBox.Show(exc.ToString());
}
}

SQL query with c# stringbuilder error near "=" symbol

I'm working on some code that creates procedures with C#. When I try to run my code:
StringBuilder sbSP1 = new StringBuilder();
sbSP1.AppendLine("CREATE PROCEDURE " + ProcN + "DELETE #id int=0 AS BEGIN DELETE FROM " + tname + " WHERE " + PK + " = #id END");
SqlConnection connection = new SqlConnection(connectionString);
using (SqlCommand cmd = new SqlCommand(sbSP1.ToString(), connection))
{
connection.Open();
cmd.CommandType = CommandType.Text;
cmd.ExecuteNonQuery();
connection.Close();
}
This part doesn't work. It throws an exception:
System.Data.SqlClient.SqlException: 'Incorrect syntax near '='.'
But when I try to run this part:
StringBuilder sbSP3 = new StringBuilder();
sbSP3.AppendLine("CREATE PROCEDURE " + ProcN + "GET AS BEGIN SET NOCOUNT ON; SELECT " + columns + " from " + tname + " END");
SqlConnection connection = new SqlConnection(connectionString);
using (SqlCommand cmd = new SqlCommand(sbSP3.ToString(), connection))
{
connection.Open();
cmd.CommandType = CommandType.Text;
cmd.ExecuteNonQuery();
connection.Close();
}
it runs correctly.
Where is my mistake in the first snippet of code?

Without sbSP1 final text it's difficult to pin down the error; as a working hypothesis I suggest that PK being complex (e.g. "id value")
should be escaped - [PK]. In order to avoid such kind of errors, please, never build the query, but make procedure's text being readable with a help of string interpolation - $ and verbatim strings - #.
//TODO: check the text, is it the procedure you want to create?
string text =
$#"create procedure [{ProcN}Delete]
#id int = 0 as
begin
delete
from [{tname}]
where [{PK}] = #id
end;";
//DONE: do not close connection manually, but wrap it into using
using (SqlConnection connection = new SqlConnection(connectionString)) {
connection.Open();
using (qlCommand cmd = new SqlCommand(text, connection)) {
cmd.ExecuteNonQuery();
}
}

how to use executereader to read one value

I want to read an int value from my table. but I faced with error
this is my code. please help me to edit my code.
sqlc = new SqlConnection(ConnectionString);
SqlCommand cmd = new SqlCommand();
cmd.CommandType = CommandType.Text;
string username = HttpContext.Current.User.Identity.Name.ToString();
cmd.CommandText = #"SELECT RemainedCharge "
+ " FROM aspnet_Users "
+ " WHERE UserName = #UserName ";
cmd.Parameters.Add(new SqlParameter("#UserName", username));
//string RemainedCharge;
sqlc.Open();
SqlDataReader rdr = cmd.ExecuteReader();
// loop over all rows returned by SqlDataReader
while(rdr.Read())
{
RemainedChargeLbl.Text=rdr.GetString(0);
}

To read one value you don't need reader. Use SqlCommand.ExecuteScalar Method which executes query and returns first column of the first row in result set returned by query:
int value = (int)cmd.ExecuteScalcar();
BTW it's better to create command object with sqlc.CreateCommand() - it creates appropriate command and automatically assigns connection to it.

You are not assigning connection object sqlc to the SqlCommand.
Add this:
cmd.Connection=sqlc;
Complete Solution:
sqlc = new SqlConnection(ConnectionString);
SqlCommand cmd = new SqlCommand();
cmd.CommandType = CommandType.Text;
cmd.Connection=sqlc;
string username = HttpContext.Current.User.Identity.Name.ToString();
cmd.CommandText = #"SELECT RemainedCharge "
+ " FROM aspnet_Users "
+ " WHERE UserName = #UserName ";
cmd.Parameters.Add(new SqlParameter("#UserName", username));
//string RemainedCharge;
sqlc.Open();
RemainedChargeLbl.Text =((int) cmd.ExecuteScalar()).ToString();

Use this code:
using (var conn = new SqlConnection(SomeConnectionString))
using (var cmd = conn.CreateCommand())
{
conn.Open();
cmd.CommandText = "SELECT RemainedCharge "
+ " FROM aspnet_Users "
+ " WHERE UserName = #UserName ";
cmd.Parameters.Add(new SqlParameter("#UserName", username);
cmd.Parameters.AddWithValue("#id", index);
using (var reader = cmd.ExecuteReader())
{
if (reader.Read())
{
learerLabel.Text = reader.GetString(reader.GetOrdinal("somecolumn"))
}
}
}

Increase performance on OleDB insert into statement, BeginTransaction CommitTransaction

I have written to append functions that insert data from custom c# list into MSAccess.
The first simply sets up a new connection for each individual recordset:
public static void appenddatatotable(string connectionstring, string tablename, string[] values)
{
var myconn = new OleDbConnection(connectionstring);
var cmd = new OleDbCommand();
cmd.CommandText = "INSERT INTO " + tablename + " ([RunDate],[ReportingGroup], [Tariff], [Year]) VALUES(#RunDate, #ReportingGroup, #Tariff, #Year)";
cmd.Parameters.AddRange(new[] { new OleDbParameter("#RunDate", values[0]), new OleDbParameter("#ReportingGroup", values[1]), new OleDbParameter("#Tariff", values[2]), new OleDbParameter("#Year", values[3])});
cmd.Connection = myconn;
myconn.Open();
cmd.ExecuteNonQuery();
myconn.Close();
}
I then simply loop over my list of values and call this function on each iteration. This works fine but is slow.
In the second function I tried to include the loop in the function and work with BeginTransction and Committransaction:
public static void appenddatatotable2(string connectionstring, string tablename, string datstr, List<PowRes> values)
{
var myconn = new OleDbConnection(connectionstring);
int icounter = 0;
var cmd = new OleDbCommand();
OleDbTransaction trans = null;
cmd.Connection = myconn;
myconn.Open();
foreach (var item in values)
{
if (icounter == 0)
{
trans = cmd.Connection.BeginTransaction();
cmd.Transaction = trans;
}
cmd.CommandText = "INSERT INTO " + tablename + " ([RunDate],[ReportingGroup], [Tariff], [Year]) VALUES(#RunDate, #ReportingGroup, #Tariff, #Year)";
if (string.IsNullOrEmpty(item.yr))
item.yr = "";
cmd.Parameters.AddRange(new[] { new OleDbParameter("#RunDate", datstr), new OleDbParameter("#ReportingGroup", item.RG), new OleDbParameter("#Tariff", item.tar), new OleDbParameter("#Year", item.yr)});
cmd.ExecuteNonQuery();
icounter++;
if (icounter >= 500)
{
trans.Commit();
icounter = 0;
}
}
if (icounter > 0)
{
trans.Commit();
}
myconn.Close();
}
This also works fine but is EVEN slower.
Is my code wrong? How could I speed up the multiple inserts?
Thanks!

did not test, just my guess for your second function: you add too many parameters to the same command over the loop - cmd.Parameters were never cleared before each usage..
normally committing large set of commands within one connection is much faster than doing them one by one at single connection.
another way to speed up your inserts is to dump all your insert statements into a long text, separated with semicolon, and then fire a commit in one go (i am not sure whether msAccess supports it or not)
EDIT:
to combine the update command into one text:
var updates = values.Select(x => string.Format("INSERT INTO myTable ([RunDate],[ReportingGroup], [Tariff], [Year]) VALUES({0}, {1}, {2}, {3})",
datstr, x.RG, x.tar, x.yr))
.Aggregate((m, n) => m + ";" + n);
cmd.CommandText = update;
Though this could have sql injection issues.

this should be significantly faster than all of your exiting versions
public static void appenddatatotable2(string connectionstring, string tablename, string datstr, List<PowRes> values)
{
string commandText = "INSERT INTO " + tablename + " ([RunDate],[ReportingGroup], [Tariff], [Year]) VALUES(#RunDate, #ReportingGroup, #Tariff, #Year)";
using (var myconn = new OleDbConnection(connectionstring))
{
myconn.Open();
using (var cmd = new OleDbCommand())
{
foreach (var item in values)
{
cmd.CommandText = commandText;
cmd.Parameters.Clear();
cmd.Parameters.AddRange(new[] { new OleDbParameter("#RunDate", datstr), new OleDbParameter("#ReportingGroup", item.RG), new OleDbParameter("#Tariff", item.tar), new OleDbParameter("#Year", item.yr) });
cmd.Connection = myconn;
cmd.Prepare();
cmd.ExecuteNonQuery();
}
}
}
}

How to run multiple SQL commands in a single SQL connection?

I am creating a project in which I need to run 2-3 SQL commands in a single SQL connection.
Here is the code I have written:
SqlConnection con = new SqlConnection(#"Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\project.mdf;Integrated Security=True");
con.Open();
SqlCommand cmd = new SqlCommand("select * from " + mytags.Text + " ", con);
SqlDataReader rd = cmd.ExecuteReader();
if (rd.Read())
{
con.Close();
con.Open();
SqlCommand cmd1 = new SqlCommand("insert into " + mytags.Text + " values ('fname.lname#gmail.com','" + TextBox3.Text + "','" + TextBox4.Text + "','" + TextBox5.Text + "','"+mytags.Text+"')", con);
cmd1.ExecuteNonQuery();
label.Visible = true;
label.Text = "Date read and inserted";
}
else
{
con.Close();
con.Open();
SqlCommand cmd2 = new SqlCommand("create table " + mytags.Text + " ( session VARCHAR(MAX) , Price int , Description VARCHAR(MAX), Date VARCHAR(20),tag VARCHAR(10))", con);
cmd2.ExecuteNonQuery();
con.Close();
con.Open();
SqlCommand cmd3 = new SqlCommand("insert into " + mytags.Text + " values ('" + Session + "','" + TextBox3.Text + "','" + TextBox4.Text + "','" + TextBox5.Text + "','" + mytags.Text + "')", con);
cmd3.ExecuteNonQuery();
label.Visible = true;
label.Text = "tabel created";
con.Close();
}
I have tried to remove the error and I got that the connection is not going to else condition. Please review the code and suggest if there is any mistake or any other solution for this.

Just change the SqlCommand.CommandText instead of creating a new SqlCommand every time. There is no need to close and reopen the connection.
// Create the first command and execute
var command = new SqlCommand("<SQL Command>", myConnection);
var reader = command.ExecuteReader();
// Change the SQL Command and execute
command.CommandText = "<New SQL Command>";
command.ExecuteNonQuery();

The following should work. Keep single connection open all time, and just create new commands and execute them.
using (SqlConnection connection = new SqlConnection(connectionString))
{
connection.Open();
using (SqlCommand command1 = new SqlCommand(commandText1, connection))
{
}
using (SqlCommand command2 = new SqlCommand(commandText2, connection))
{
}
// etc
}

Just enable this property in your connection string:
sqb.MultipleActiveResultSets = true;
This property allows one open connection for multiple datareaders.

I have not tested , but what the main idea is: put semicolon on each query.
SqlConnection connection = new SqlConnection();
SqlCommand command = new SqlCommand();
connection.ConnectionString = connectionString; // put your connection string
command.CommandText = #"
update table
set somecol = somevalue;
insert into someTable values(1,'test');";
command.CommandType = CommandType.Text;
command.Connection = connection;
try
{
connection.Open();
}
finally
{
command.Dispose();
connection.Dispose();
}
Update:
you can follow
Is it possible to have multiple SQL instructions in a ADO.NET Command.CommandText property? too

This is likely to be attacked via SQL injection by the way. It'd be worth while reading up on that and adjusting your queries accordingly.
Maybe look at even creating a stored proc for this and using something like sp_executesql which can provide some protection against this when dynamic sql is a requirement (ie. unknown table names etc). For more info, check out this link.

No one has mentioned this, but you can also separate your commands using a ; semicolon in the same CommandText:
using (SqlConnection conn = new SqlConnection(connString))
{
using (SqlCommand comm = new SqlCommand())
{
comm.Connection = conn;
comm.CommandText = #"update table ... where myparam=#myparam1 ; " +
"update table ... where myparam=#myparam2 ";
comm.Parameters.AddWithValue("#myparam1", myparam1);
comm.Parameters.AddWithValue("#myparam2", myparam2);
conn.Open();
comm.ExecuteNonQuery();
}
}

Multiple Non-query example if anyone is interested.
using (OdbcConnection DbConnection = new OdbcConnection("ConnectionString"))
{
DbConnection.Open();
using (OdbcCommand DbCommand = DbConnection.CreateCommand())
{
DbCommand.CommandText = "INSERT...";
DbCommand.Parameters.Add("#Name", OdbcType.Text, 20).Value = "name";
DbCommand.ExecuteNonQuery();
DbCommand.Parameters.Clear();
DbCommand.Parameters.Add("#Name", OdbcType.Text, 20).Value = "name2";
DbCommand.ExecuteNonQuery();
}
}

Here you can find Postgre example, this code run multiple sql commands (update 2 columns) within single SQL connection
public static class SQLTest
{
public static void NpgsqlCommand()
{
using (NpgsqlConnection connection = new NpgsqlConnection("Server = ; Port = ; User Id = ; " + "Password = ; Database = ;"))
{
NpgsqlCommand command1 = new NpgsqlCommand("update xy set xw = 'a' WHERE aa='bb'", connection);
NpgsqlCommand command2 = new NpgsqlCommand("update xy set xw = 'b' where bb = 'cc'", connection);
command1.Connection.Open();
command1.ExecuteNonQuery();
command2.ExecuteNonQuery();
command2.Connection.Close();
}
}
}

using (var connection = new SqlConnection("Enter Your Connection String"))
{
connection.Open();
using (var command = connection.CreateCommand())
{
command.CommandText = "Enter the First Command Here";
command.ExecuteNonQuery();
command.CommandText = "Enter Second Comand Here";
command.ExecuteNonQuery();
//Similarly You can Add Multiple
}
}
It worked for me.