ok so the first problem is the connection string itself it has this exception that i do not understand so i tried to put it in a try catch syntax but as i inserted it in the public partial class Form1 : Form the parenthesis are acting up so i inserted it in a function and now the fuction has this error:
Severity Code Description Project File Line Suppression State
Error CS0161 'Form1.connection()': not all code paths return a value Restaurant Management System C:\Users\admin\source\repos\Restaurant Management System\Restaurant Management System\Form1.cs 36 Active
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace Restaurant_Management_System
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
panel1.BackColor = Color.FromArgb(50, Color.Black);
label1.BackColor = Color.FromArgb(30, Color.Beige);
label2.BackColor = Color.FromArgb(0, Color.Black);
Password.BackColor = Color.FromArgb(0, Color.Black);
}
SqlCommand cmd;
SqlDataReader dr;
public SqlConnection connection()
{
try
{
SqlConnection con = new SqlConnection("Data Source=(LocalDB)\\MSSQLLocalDB;AttachDbFilename= \"|Data Directory|\\Coffee(LoginEmployee).mdf\";Integrated Security=True;");
}
catch (Exception ex)
{
MessageBox.Show("Error message: COULD NOT CONNECT STRING: " + ex);
}
}
private string getUsername()
{
SqlConnection con = connection();
cmd = new SqlCommand("SELECT nalue FROM EmployeeLog where Property=Username", con);
dr = cmd.ExecuteReader();
dr.Read();
return dr[0].ToString();
}
private string getPassword()
{
SqlConnection con = connection();
cmd = new SqlCommand("SELECT nalue FROM EmployeeLog where Property=Password", con);
dr = cmd.ExecuteReader();
dr.Read();
return dr[0].ToString();
}
What do i need to replace? why does it not all return a value? if i use the void case it will also have this error that i cannot explicitly convert it to sqlconnection. this is made in the latest visual studio 2017
If you catch the exception, no SqlConnection will be returned. So you could return null after showing the message box.
Then of course, you will need to do a null check after calling connection() so you don't get a null reference exception trying to use it.
You also need to return the connection you are creating:
return new SqlConnection("Data Source=(LocalDB)\\MSSQLLocalDB;AttachDbFilename=|Data Directory|Coffee(LoginEmployee).mdf;Integrated Security=True;");
Note: I don't recommend hard-coding your connection string either! You would normally add the connection string to your app.config/web.config and read it using ConfigurationManager.ConnectionStrings... - this is because you might have different instance names on different machines, or you might want to point to a database on a server rather than local. You will not need to change the code and recompile just to make it work on more than one machine.
There is information on microsoft's class library site (https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnectionstringbuilder.attachdbfilename(v=vs.110).aspx) saying: An error will be generated if a log file exists in the same directory as the data file and the 'database' keyword is used when attaching the primary data file. In this case, remove the log file. Once the database is attached, a new log file will be automatically generated based on the physical path.
Related
I tried to create a CLR stored procedure in VS2017 but encountering error "NOT Connected." while executing that stored procedure.
I need to connect to other database server to grab some data. Therefore I cannot use context=true in SqlConnection.
Stored procedure will be created in serverA
This stored procedure will query data from serverB
Data will be stored back to serverA.
Is there anything I need to do in order to have regular connection in CLR stored procedure?
Please advise. Thanks!
using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
public partial class StoredProcedures
{
[Microsoft.SqlServer.Server.SqlProcedure]
public static void udp_CLR_GetData()
{
string ConnStr = "server=MyServer; database=MyDB; user id=accabc; password=abc123";
string sql = " select top 1 ID from [dbo].Table1 ";
SqlDataReader dr = null;
DataTable dt = new DataTable();
try
{
using (SqlConnection fcon = new SqlConnection(ConnStr))
{
if (fcon.State == ConnectionState.Open)
{
SqlContext.Pipe.Send("Connected.");
using (SqlCommand fcmd = new SqlCommand(sql, fcon))
{
SqlContext.Pipe.Send("Before executing reader...");
dr = fcmd.ExecuteReader();
SqlContext.Pipe.Send("After executing reader...");
SqlContext.Pipe.Send("Before send...");
SqlContext.Pipe.Send(dr);
SqlContext.Pipe.Send("After send...");
}
}
else
{
SqlContext.Pipe.Send("NOT Connected.");
}
}
}
catch(Exception ex)
{
SqlContext.Pipe.Send("Exception error (udp_CLR_GetData): " + ex.Message);
}
finally
{
if(dr != null && !dr.IsClosed)
{
dr.Close();
}
}
}
}
Creating a new instance of a SqlConnection in:
using (SqlConnection fcon = new SqlConnection(ConnStr))
does not create it in an "open" state. You need to actually open it for it to be "open". So, I would remove the if (fcon.State == ConnectionState.Open) and the associated else part of it. I would also remove the SqlContext.Pipe.Send("Connected."); line.
Then, just before the dr = fcmd.ExecuteReader(); line, add a line for:
fcon.Open();
This way you open the connection and immediately execute the command. No need to open the connection only to do other work getting the command ready.
For more info on working with SQLCLR in general, please visit: SQLCLR Info
Try defining the data source in the connection string instead of server
string ConnStr = "DataSource=MyServer;Initial Catalog=MyDB;User Id=accabc;Password=abc123";
other than that, make sure clr is enabled on the server:
https://learn.microsoft.com/en-us/sql/relational-databases/clr-integration/clr-integration-enabling?view=sql-server-ver15
I got a question about c# and mysql. I would like to make a very simpel login form that is connected to my local db. I got the connection to work (tested it) but i have a problem with reading my data that is returned from a select.
I'm trying to put an ID into a string so I can display it(this is just for testing). Now I have searched a lot on google and almost everyone has something like this. When I execute it doesn't give error but my sqldatareader finds nothing. In the first if I ask if it has got any rows and there are none.
What am I doing wrong? My username/password do exist in my db.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using MySql.Data.MySqlClient;
namespace eindwerk
{
public partial class LoginForm : Form
{
string myConnection = "Server=localhost;Database=mydb;Uid=root;Pwd=root;";
MySqlCommand cmd;
MySqlConnection connection;
public LoginForm()
{
InitializeComponent();
connection = new MySqlConnection(myConnection);
connection.Open();
}
private void loginForm_Load(object sender, EventArgs e)
{
this.Location = new Point((Screen.PrimaryScreen.WorkingArea.Width - this.Width) / 2,
(Screen.PrimaryScreen.WorkingArea.Height - this.Height) / 2);
}
private void btnLogin_Click(object sender, EventArgs e)
{
try
{
cmd = connection.CreateCommand();
cmd.CommandText = "SELECT idlogin FROM login WHERE (username='#username') AND (password='#password') LIMIT 1;";
cmd.Parameters.AddWithValue("#username", txtbxLoginUsername.Text);
cmd.Parameters.AddWithValue("#password", txtbxLoginPassword.Text);
MySqlDataReader rdr = cmd.ExecuteReader();
rdr.Read();
if (rdr.HasRows)
{
while (rdr.Read())
{
label1.Text = rdr.GetInt32("idlogin").ToString();
}
}
else
{
lblLoginError.Visible = true;
}
rdr.Close();
}
catch {
lblLoginError.Text = "Nope";
lblLoginError.Visible = true;
}
}
}
}
You are calling Read() Multiple time. Call the While(Reader.Read()) single time and check the result by if(rdr.HasRows()){} for check result is return or nothing is come in the response.
You are returning only 1 row, but you are calling Read() twice. Your row is effectively discarded before you look at your data.
After a long search i have found the problem ! In my sql query i put username='#username', there lies the problem. You can't use single quotes !!!. I removed the quotes and it works perfectly.
That is whay you get for trusthing a search result on the third page of google...
Thanks to all !
i have a little problem with my C# code(im normally a c++ dev so i just know most of the basics of c#)
I wanted to write a class to execute a SQL query using that programm but atm it does nothing and i don´t get any error from it.
The MySqlConnectionHandler Class which i wrote:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MySql.Data.MySqlClient;
using System.Windows.Forms;
namespace WS_Studio_tool
{
class MySqlConnectionHandler
{
private MySqlConnection connection;
private string ConnectionString;
public MySqlConnectionHandler()
{
try
{
ConnectionString = "SERVER=localhost;" +
"DATABASE=ws_creator_beta;" +
"UID=root;" +
"PASSWORD=AF362GL!";
connection = new MySqlConnection(ConnectionString);
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
System.Windows.Forms.MessageBox.Show(ex.Message, "MySql Fehler!");
}
}
public bool InsertRow(string SQL_Query)
{
try
{
MySqlCommand command = connection.CreateCommand();
command.CommandText = SQL_Query;
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
System.Windows.Forms.MessageBox.Show(ex.Message, "MySql Fehler!");
}
return true;
}
}
}
My Function Call(I played a lot with it so it could contain things that are not necessary):
string newquery = QueryTextBox1.ToString();
MySqlConnectionHandler SqlHandler = new MySqlConnectionHandler();
SqlHandler.InsertRow(newquery);
And my MySql Query:
INSERT INTO user_data (username,passwd) VALUES ('asdf', 'asdf');
It would be very nice if somebody could take a quick look at it, maybe you are able to find the error..
You're not telling the command to execute: also, you need to explicitly open the connection before using it, so add these lines to InsertRow:
connection.Open();
command.ExecuteNonQuery();
I'd also suggest disposing of the connection once you're done with it - either by implementing IDisposable on the MySqlConnectionHandler class, or - easier - just create a connection within a using block when executing the query:
using (var connection = new new MySqlConnection(ConnectionString))
{
using (var command = connection.CreateCommand())
{
command.CommandText = SQL_Query;
connection.Open();
command.ExecuteNonQuery();
}
}
You did not call command.Execute, so your SQL never gets executed.
I want to write a MySql statement that will connect to the database, select a column from the table, then output that data to a text file to a specific location on my computer. I have searched the internet for a couple days now and don't seem to find the answer I am looking for. I am fairly new to c#, MySql, and Visual Studio. I am just trying to learn how to write the correct statements and get the desired result. Any help would be greatly appreciated.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MySql.Data.MySqlClient;
using MySql.Data;
using System.Windows.Forms;
using System.IO;
namespace NewPractice
{
public class Connect
{
static void Main()
{
string results = #"server=111.111.11.111; userid=anyone;
password=anypassword; database=anydatabase";
MySqlConnection conn = null;
try
{
conn = new MySqlConnection(results);
conn.Open();
//Console.WriteLine(
File.WriteAllLines(
#"C:\Documents and Settings\anyone\My Documents\Tests\testoutput.txt",
results.ToArray());
}
catch (MySqlException ex)
{
Console.WriteLine("Error: (0)", ex.ToString());
}
finally
{
if (conn != null)
{
conn.Close();
}
}
}
}
}
You're writing the contents of the result string to the file, not the data you're attempting to select. You need to run a sql command and get a SqlDataReader object to write your data to the file.
string results = #"server=111.111.11.111; userid=anyone;
password=anypassword; database=anydatabase";
MySqlConnection connection = new MySqlConnection(results);
MySqlCommand command = connection.CreateCommand();
MySqlDataReader reader;
command.CommandText = "select * from mycustomers";
connection.Open();
reader = command.ExecuteReader();
using(var sw = new StreamWriter("C:\MyPath\MyFile.txt"))
{
while (reader.Read())
{
var row = (IDataRecord)reader;
sw.WriteLine(row["myColumn"]);
}
}
connection.Close();
If the database is on your local machine you can use 'select .. into outfile'. http://dev.mysql.com/doc/refman/5.1/en/select-into.html. This will write to a folder on the server so it's not v useful if it's a different machine and you can't copy from there.
There are plenty of tutorials out there for accessing MySQL from .NET.
This is one: http://zetcode.com/db/mysqlcsharptutorial/
In any language, there are a few simple steps to read from a database:
1. connect to the database.
2. execute a query
3. iterate through the results of the query
4. close the connection.
What you are doing in your code is connecting to the database and then trying to write the connection information to a file.
Guys I searched around like hell but nothing could help me so I think it's time to ask. Before I write to problem, I need to say that I need it's solution asap because it's a project that I have to give tomorrow and I stuck on the same subject since ages and still losing time.
OK here it is;
I need to add a book to a library system, at first phase I add the standard book features which has only "one value" like (name, page number, publishing time, publisherID etc) but as wanted by me book MAY HAVE MULTIPLE WRITERS AND CATEGORIES which killed me and still I can't resolve. I tried to add book to it's (books) table then with the information i got from that i did an other insert op. to (bookWriters) table. While I check it, compiler does everything in order without error but when I check table from SQL Server there is nothing.
Here is what I tried to do;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Data.SqlClient;
namespace Project_
{
public partial class addBook: Form
{
public addBook()
{
InitializeComponent();
}
public main refForm;
int chosenWritersNumber; //how many writers have selected on listbox
int[] writers= { }; // an array list that i keep writerIDs that comes from class
int ind = 0;
int insertedBookID; // to catch latest added book's ID
int chosenWriterID; // writer that will be added
private void bookAddingPreps()
{
chosenWritersNumber = lstWriters.SelectedItems.Count;
Array.Resize<int>(ref writers, chosenWritersNumber );
for (int i = 0; i < chosenWritersNumber ; i++)
{
writers[i] = ((X_Writers)lstWriters.SelectedItems[i]).XWriterID;
}
}
private void addMainBookInfos()
{
SqlConnection con = new SqlConnection(Conn.Activated);
SqlCommand com = new SqlCommand("AddBook", con);
com.CommandType = CommandType.StoredProcedure;
com.Parameters.AddWithValue("#BookISBN", txtISBN.Text);
con.Close();
}
private void catchAddedBookID()
{
SqlConnection con = new SqlConnection(Conn.Activated);
SqlCommand com = new SqlCommand("catchBookID", con);
com.CommandType = CommandType.StoredProcedure;
con.Open();
SqlDataReader dr = com.ExecuteReader();
if (dr.HasRows)
{
while (dr.Read())
{
insertedBookID = dr.GetInt32(0);
}
}
dr.Close();
con.Close();
}
private void addWritersOfTheBook()
{
chosenWriterID = writers[ind];
SqlConnection con = new SqlConnection(Conn.Activated);
SqlCommand com = new SqlCommand("addBookWriters", con);
com.CommandType = CommandType.StoredProcedure;
com.Parameters.AddWithValue("#BookID", insertedBookID);
com.Parameters.AddWithValue("#WriterID", chosenWriterID);
con.Close();
}
I call these methods on click of a button. You see also stored procedure names but as I checked they all correct, there must be a mistake in this page that I still cant see but if it's needed I can add what procedures writes but they all tested and seems working.
So as i said, when i do this, as ind = 0, a writer should have been added, break point shows everything is ok and compiler doesnt show any errors but when I check sql server table, its empty.
Written in C# with using Visual Studio 2010 Ultimate and SQL Server 2008 Dev.
Thanks
You forget to execute your SqlCommand's. Make a call to command.ExecuteNonReader(); to execute it without expecting any results. see: http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.aspx
Apart form that, dont forget to dispose the resources acquired in your methods. Something like:
private void addMainBookInfos()
{
using (SqlConnection con = new SqlConnection(Conn.Activated))
using (SqlCommand com = new SqlCommand("AddBook", con))
{
com.CommandType = CommandType.StoredProcedure;
com.Parameters.AddWithValue("#BookISBN", txtISBN.Text);
com.ExecuteNonQuery()
// close can be omitted since you are already using the 'using' statement which automatically closes the connection
con.Close();
}
}