C＃-从另一个类写入Form变量

Question

In brief, One class is responsible for initialization and main GUI controls, while another does all the requests, data collection and returns the results which can take a bit of time to be completely finished.

I have no problems passing data from 2nd to gui class (let's call this a main class) once it's all been collected by using public vars. However, writing directly to the form from 2nd class doesn't seem to be so straight forward.

What I tried to do was in the 2nd class make a instance of the main class, then inside a method of 2nd class repeatedly call the public method from the main class which will write the data directly to the form. That was the theory at least.

So it looks like this:

2nd class:

Gui r1 = new Gui(); 
// ...
result += someVar + "\n";
// ...
r1.setResultsInfo(result);


// method inside the main class for writing to form:

public partial class Gui : Form
{
    public void setResultsInfo(String var)
    {
        resultsInfo.Text += var;  
    }
}

However, this doesn't write anything to the Form. Accessing and writing to resultsInfo directly from the main class works fine, just not from the 2nd class through an instance of the main class. I guess it could be because it's trying to write to some another instance of not really existent r1 form, but how I'am supposed to access my active form if I obviously can't access the main class without creating an instance of it?

Updated Code with more details:

public partial class Gui : Form
    {

        public Gui Instance;

        public Gui()
        {
            Instance = this;
            InitializeComponent();

        }


// 2nd class: 


static class Program
{


    public static QueryResult[] arr = new QueryResult[20];
    public static string result;

    [STAThread]





    private static void QueryAPIAndPrintResult(string term, string location)
    {

        Gui r1 = new Gui();

        string var;


        System.Console.WriteLine(var = "Ieškoma: '" + term + "' \nvietovėje: '" + location + "'");


        result += var + "\n";

        r1.Instance.setResultsInfo(var); 
        // Gui.Instance.setResultsInfo() // throws error about requiring an instance. 
        // ... 
    }

        // ...
} 


//  main method: 


 static void Main(string[] args)
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new Gui());
    }

Answer 1

Where are you trying to look for the written data? You are creating a new instance of Gui and, as per the code you posted, you are never even showing that Form.

I would suggest you to take a look at the Singleton Pattern , and do something like this:

public class Gui
{
    public static Gui Instance;

    Gui()
    {
        // constructor stuff
        Instance = this;
    }
}

// from your other class
// ...
result += someVar + "\n";
// ...
Gui.Instance.setResultsInfo(result);