In my code below, the cmdquery works but the hrquery does not. How do I get another query to populate a grid view? Do I need to establish a new connection or use the same connection? Can you guys help me? I'm new to C# and asp. Here's some spaghetti code I put together. It may all be wrong so if you have a better way of doing this feel free to share.
if (Badge != String.Empty)
{
string cmdquery = "SELECT * from Employees WHERE Badge ='" + Badge + "'";
string hrquery = "SELECT CLOCK_IN_TIME, CLOCK_OUT_TIME FROM CLOCK_HISTORY WHERE Badge ='" + Badge + "'";
OracleCommand cmd = new OracleCommand(cmdquery);
cmd.Connection = conn;
cmd.CommandType = CommandType.Text;
conn.Open();
OracleDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
this.xUserNameLabel.Text += reader["EMPLOYEE_NAME"];
this.xDepartmentLabel.Text += reader["REPORT_DEPARTMENT"];
}
OracleCommand Hr = new OracleCommand(hrquery);
Hr.Connection = conn;
Hr.CommandType = CommandType.Text;
OracleDataReader read = Hr.ExecuteReader();
while (read.Read())
{
xHoursGridView.DataSource = hrquery;
xHoursGridView.DataBind();
}
}
conn.Close();
Your data access code should generally look like this:
string sql = "SELECT * FROM Employee e INNER JOIN Clock_History c ON c.Badge = e.Badge WHERE e.Badge = #BadgeID";
using (var cn = new OracleConnection("your connection string here"))
using (var cmd = new OracleCommand(sql, cn))
{
cmd.Parameters.Add("#BadgeID", OracleDbType.Int).Value = Badge;
cn.Open();
xHoursGridView.DataSource = cmd.ExecuteReader();
xHoursGridView.DataBind();
}
Note that this is just the general template. You'll want to tweak it some for your exact needs. The important things to take from this are the using blocks to properly create and dispose your connection object and the parameter to protect against sql injection.
As for the connection question, there are exceptions but you can typically only use a connection for one active result set at a time. So you could reuse your same conn object from your original code, but only after you've completely finished with it from the previous command. It is also okay to open up two connections if you need them. The best option, though, is to combine related queries into single sql statement when possible.
I'm not even going to get into how you should be using usings and methods :p
if (Badge != String.Empty)
{
string cmdquery = "SELECT * from Employees WHERE Badge ='" + Badge + "'";
string hrquery = "SELECT CLOCK_IN_TIME, CLOCK_OUT_TIME FROM CLOCK_HISTORY WHERE Badge ='" + Badge + "'";
OracleCommand cmd = new OracleCommand(cmdquery);
cmd.Connection = conn;
cmd.CommandType = CommandType.Text;
conn.Open();
OracleDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
this.xUserNameLabel.Text += reader["EMPLOYEE_NAME"];
this.xDepartmentLabel.Text += reader["REPORT_DEPARTMENT"];
}
OracleCommand Hr = new OracleCommand(hrquery);
Hr.Connection = conn;
Hr.CommandType = CommandType.Text;
OracleDataReader read = Hr.ExecuteReader();
//What's this next line? Setting the datasource automatically
// moves through the data.
//while (read.Read())
//{
//I changed this to "read", which is the
//datareader you just created.
xHoursGridView.DataSource = read;
xHoursGridView.DataBind();
//}
}
conn.Close();
Related
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());
}
}
I am trying to insert data into a database that I have that has a table called EmployeeInfo
The user is prompted to enter a last name and select a department ID (displayed to the user as either marketing or development) The column ID automatically increments.
Here is my Code behind
protected void SubmitEmployee_Click(object sender, EventArgs e)
{
var submittedEmployeeName = TextBox1.Text;
var submittedDepartment = selectEmployeeDepartment.Text;
if (submittedEmployeeName == "")
{
nameError.Text = "*Last name cannot be blank";
}
else
{
System.Data.SqlClient.SqlConnection sqlConnection1 =
new System.Data.SqlClient.SqlConnection("ConnString");
System.Data.SqlClient.SqlCommand cmd = new System.Data.SqlClient.SqlCommand();
cmd.CommandType = System.Data.CommandType.Text;
cmd.CommandText = "INSERT INTO EmployeeInfo (LastName, DepartmentID ) VALUES ('" + submittedEmployeeName + "', " + submittedDepartment + ")";
cmd.Connection = sqlConnection1;
sqlConnection1.Open();
cmd.ExecuteNonQuery();
sqlConnection1.Close();
}
}
The error I'm recieving is 'Arguement exception was unhandled by user code'
Here is a picture of it.
As requested. More details
If I had enough reputation, I would rather post this as a reply, but it might actually be the solution.
The reason why it stops there is because you are not providing a legit SqlConnection, since your input is: "ConnString", which is just that text.
The connection string should look something like:
const string MyConnectionString = "SERVER=localhost;DATABASE=DbName;UID=userID;PWD=userPW;"
Which in your case should end up like:
System.Data.SqlClient.SqlConnection sqlConnection1 = new System.Data.SqlClient.SqlConnection(MyConnectionString);
Besides that, you should build your connections like following:
using (SqlConnection con = new SqlConnection(MyConnectionString)) {
using (SqlCommand cmd = new SqlCommand())
{
cmd.CommandText = xxxxxx; // Your query to the database
cmd.Connection = con;
cmd.Connection.Open();
cmd.ExecuteNonQuery();
}
}
This will do the closing for you and it also makes it easier for you to nestle connections. I did a project recently and did the connection your way, which ended up not working when I wanted to do more than one execute in one function. Just important to make a new command for each execute.
I've seen this question asked a couple times but I couldn't find a good answer. I've been stuck for hours on this.
Basically I have usernames saved in a database and when a new user registers I want to check if his username is available - and if it is available add him to the database. And they register through a textbox called FName. The table is called Users.
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
SqlCommand cmd = new SqlCommand("SELECT FName FROM Users WHERE FName = ????? usernames????? ", con);
con.Open();
SqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
Console.WriteLine(reader["text"].ToString());
}
How can I fix this code?
"SELECT FName FROM Users WHERE FName = #paramUsername"
and then you insert the parameter into the cmd like so:
cmd.Parameters.Add("paramUsername", System.Data.SqlDbType.VarChar);
cmd.Parameters["paramUsername"].Value = "Theusernameyouarelookingfor";
Check this out:
SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
string validationQuery = "SELECT * FROM Users WHERE FName = #name";
SqlCommand validationCommand = new SqlCommand(validationQuery, connection);
validationCommand.Parameters.Add("#name", SqlDbType.VarChar).Value = loginUserSelected;
connection.Open();
SqlDataReader validationReader = validationCommand.ExecuteReader(CommandBehavior.CloseConnection);
if (!validationReader.Read())
{
string insertQuery = "INSERT INTO Users (FName) VALUES (#name)";
SqlCommand insertCommand = new SqlCommand(insertQuery, connection);
insertCommand.Parameters.Add("#name", SqlDbType.VarChar).Value = loginUserSelected;
connection.Open();
insertCommand.ExecuteNonQuery();
insertCommand.Dispose();
connection.Close();
}
else
{
//Uh oh, username already taken
}
validationReader.Close();
validationCommand.Dispose();
Things to note:
Use parameters, avoid concatenating strings because it's a security vulnerability
Always Close and Dispose your ADO objects
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.
I've just read all the answers about the same problem but they have not helped.
This is a part of my c# code that is too long. It has a lot of SQLConnections and 2 timers.
Indirizzo nuovoInd = new Indirizzo();
SqlConnection cn = new SqlConnection(nuovoInd.OttieniIP());
string strSql = "INSERT INTO Pietanze(nome,prezzo,ingredienti,cod_cat) VALUES ('"+nome+"','"+prezzo+"','"+ingredienti+"','"+contCat+"')";
SqlCommand cmd = new SqlCommand(strSql, cn);
cn.Open();
SqlDataReader dr = cmd.ExecuteReader();
or
public static float GetCoperti(int codOrdine)
{
float copertiTot = 0;
List<Ordine> ordini = new List<Ordine>();
VisualizzaOrdini.Form1.Indirizzo nuovoInd = new VisualizzaOrdini.Form1.Indirizzo();
SqlConnection cn = new SqlConnection(nuovoInd.OttieniIP());
string strSql = "SELECT codo,tavolo,InsertDate,nCoperti,costoCoperti FROM Ordini, Riga_Ordine, Coperti where codo=cod_or and cod_or = '"+ codOrdine + "' ORDER BY InsertDate DESC";
SqlCommand cmd = new SqlCommand(strSql, cn);
cn.Open();
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
Ordine currO = new Ordine();
currO.Data = Convert.ToDateTime(dr["InsertDate"]);
currO.Coperti = (int)dr["nCoperti"];
currO.PrezzoCoperto = Convert.ToSingle(dr["costoCoperti"]);
currO.Tavolo = dr["tavolo"].ToString();
currO.Codice = (int)dr["codo"];
copertiTot = (currO.PrezzoCoperto * Convert.ToSingle(currO.Coperti));
ordini.Add(currO);
}
return copertiTot;
}
I'm struggling with the fact that the code is throwing an OutOfMemoryException. What might be causing this? How do I resolve it?
It may be the problem that you are not Closing your SqlDataReader object after fetching records, You have to close it explicitly.
dr.Close();
And also, Close your connection after closing reader, or use using block as suggested by Habib.
cn.Close();
First, having your database connection open for the full execution of code is bad practice. Assign the execute statement to some DataTable. It will provide you the local copy of the database. It's also more convenient to process and you surely don't get out of memory exceptions.
Datatable DTab = cmdexecuteReader();
DataSet DSet = cmdexecuteReader();
Both Will give you expectedd results always.