数据库更新不起作用

Question

As in title. I tried to do everything, I searched on internet everywhere but it doesn't work. Here's the code:

public void SetIP(String IP, String Username)
    {
        try
        {
            String commandString = "UPDATE `Users` SET `IP` = '@ip' WHERE 'Username' = '@user';";
            command = new MySqlCommand(commandString, connection);
            command.Parameters.AddWithValue("@ip", IP);
            command.Parameters.AddWithValue("@user", Username);

            command.BeginExecuteNonQuery();
        }
        catch (Exception e)
        {
            MessageBox.Show(e.Message);
        }

    }

I Correctly put both of values into Strings IP and Username. I get Username from TextBox and IP adress by doing this code:

public String GetIP()
    {
        String direction = "";
        WebRequest request = WebRequest.Create("http://checkip.dyndns.org/");
        using (WebResponse response = request.GetResponse())
        using (StreamReader stream = new StreamReader(response.GetResponseStream()))
        {
            direction = stream.ReadToEnd();
        }

        //Search for the ip in the html
        int first = direction.IndexOf("Address: ") + 9;
        int last = direction.LastIndexOf("</body>");
        direction = direction.Substring(first, last - first);

        return direction;
    }

And I just call method SetIP like this: SetIP(GetIP(), UsernameBox.Text); But when I come to the database to check if it changed it's still the same. All the time.

//Edit: Got this error command: "There is already an open DataReader associated with this Connection which must be closed first."

I use this DataReaders:

public bool FindUsername(String Username)
    {
        String commandString = "select * from Users where Username = '" + Username + "';";
        command = new MySqlCommand(commandString, connection);

        MySqlDataReader connectionReader = command.ExecuteReader();
        if (connectionReader.Read())
        {
            connectionReader.Close();
            return true;
        }
        else
        {
            connectionReader.Close();
            return false;
        } 
    }
public bool FindEmail(String Email)
    {
        String commandString = "select * from Users where Email = '" + Email + "';";
        command = new MySqlCommand(commandString, connection);

        MySqlDataReader connectionReader = command.ExecuteReader();

        if (connectionReader.Read())
        {
            connectionReader.Close();
            return true;
        }
        else
        {
            connectionReader.Close();
            return false;
        } 
    }
public bool LoginSystem_FindUser(String Username, String Password)
    {
        String commandString = "select * from Users where Username = '"+Username+"' and Password = '"+Password+"' ;";
        command = new MySqlCommand(commandString, connection);

        MySqlDataReader connectionReader = command.ExecuteReader();
        if (connectionReader.Read())
        {
            return true;
        }
        else
        {
            connectionReader.Close();
            return false;
        } 
    }

I'm using only "LoginSystem_FindUser" and after that SetIP, FindUser and FindEmail I use only for registration.

Answer 1

'Username' = '@user'

will always return to false because it compares literally.

It's because you parameters were wrapped with single quotes. Remove the single quotes and it will work.

String commandString = "UPDATE `Users` SET `IP` = @ip WHERE Username = @user;";

One more thing, column names are identifiers so they should also not be surrounded with single quotes.

Answer 2

I got it. I forgot

connectionReader.Close();

after if statement. Thanks BTW.