an error on connectionstring

Question

there is an error red underline on (connectionString)which said that the name'ConnectionString' does not exist in the current context. Do i need to declare sth before i use the using statement?

SqlConnection conn = new SqlConnection("Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True") ; 

    using (SqlConnection connection = new SqlConnection(connectionString)
    {
        connection.Open();

        using (SqlCommand command = new SqlCommand(
        "SELECT product.P_ID, Product.P_Name,Product.Leadtime, Product.SafetyStockamount," +
        "Monthlysales.Month, Monthlysales.totalsalesamount, (totalsalesamount/30) as Averagedailysales, ((totalsalesamount/30) * Leadtime + SafetyStockamount) as reorderpoint " +
        "FROM Product, Monthlysales " +
        "where Product.P_ID = Monthlysales.P_ID AND Product.P_ID =@P_ID AND Monthlysales.Month =@Month ", connection))
        {

            command.Parameters.Add(new SqlParameter("P_ID", pid));
            command.Parameters.Add(new SqlParameter("Month", Startmonth));
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            DataSet ds = new DataSet();
            adapter.Fill(ds);
            // now you have the data in Dataset ds
        }

Answer 1

In using statement, you want to get value of connectionString. But there is not any variable.

Change

SqlConnection conn = new SqlConnection("Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True") ; 

to

string connectionString= "Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True"; 

---

Also, you have not ending bracket in using statement.

 using (SqlConnection connection = new SqlConnection(connectionString))

Answer 2

As your code

SqlConnection conn = new SqlConnection("Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True") ; 

You are making instance of connection that is not connectionstring. make it String connectionString and pass them as parameter to SqlConnection.

Answer 3

If you are completely sure about your connectionString, user this code :

 using (SqlConnection connection = new SqlConnection("Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True"))
    {
        connection.Open();

        using (SqlCommand command = new SqlCommand(
        "SELECT product.P_ID, Product.P_Name,Product.Leadtime, Product.SafetyStockamount," +
        "Monthlysales.Month, Monthlysales.totalsalesamount, (totalsalesamount/30) as Averagedailysales, ((totalsalesamount/30) * Leadtime + SafetyStockamount) as reorderpoint " +
        "FROM Product, Monthlysales " +
        "where Product.P_ID = Monthlysales.P_ID AND Product.P_ID =@P_ID AND Monthlysales.Month =@Month ", connection))
        {

            command.Parameters.Add(new SqlParameter("P_ID", pid));
            command.Parameters.Add(new SqlParameter("Month", Startmonth));
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            DataSet ds = new DataSet();
            adapter.Fill(ds);
        }
    }