Error: “an object reference is required for the non-static field, method or property…”

Question

I have a WPF client programmed with c#. The program is a register demo, you type a name and say if they are here or not and send it to a server and port that is entered into a textbox by the user.

When trying to apply this in the code however, I get the error: “an object reference is required for the non-static field, method or property…”. This is on the "client.connect" line...

namespace client
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        public MainWindow()
        {
            InitializeComponent();
        }

        public class connectandsend
        {

            //if 'REGISTER' button clicked do this...{
            static void connect()
            {
                TcpClient client = new TcpClient(); // New instance of TcpClient class of the .Net.Sockets
                client.Connect(server_txt.Text, Convert.ToInt32(port_txt.Text)); // Server, Port
                StreamWriter sw = new StreamWriter(client.GetStream()); // New StreamWriter instance
                StreamReader sr = new StreamReader(client.GetStream()); // New StreamReader instance
            }

            /* static void send()
            {
                stream write... name.text and 'here' or 'not here' ticked box?
            }

            }
            */
        }

    }
}

Answer 1

The connect() method cannot be static if you want to be able to access any non-static members of the MainWindow in it. Also it cannot be located in another class unless this class or the method itself also has a reference to the MainWindow class.

Remove the static keyword and move the method to the MainWindow class:

public partial class MainWindow : Window
{

    public MainWindow()
    {
        InitializeComponent();
    }

    void connect()
    {
        ...
    }
}

Or pass the server_txt.Text and port_txt.Text to the method when you call it:

static void connect(string server, int port)
{
    TcpClient client = new TcpClient(); // New instance of TcpClient class of the .Net.Sockets
    client.Connect(server, port); // Server, Port
    StreamWriter sw = new StreamWriter(client.GetStream()); // New StreamWriter instance
    StreamReader sr = new StreamReader(client.GetStream()); // New StreamReader instance
}

MainWindow:

connectandsend.connect(server_txt.Text, Convert.ToInt32(port_txt.Text));