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C# Call method from another class

I've tried the bellow code which is working but it keeps opening multiple forms every time i call calltest() method. How can i call test() method without opening it's form? Should i move all my methods to another class file? Thanks
namespace test1
{
public partial class MainForm : Form
{
public void test()
{
//code
}
...
}
}
namespace test1
{
public partial class SecondForm : Form
{
private void calltest()
{
MainForm form1 = new MainForm();
form1.test();
}
...
}
}

You might want to reconsider your design. However, here is a direct answer to your question:
The issue you are having is because each time in the calltest method, you are creating a new instance of MainForm.
Instead, you should inject the original instance of MainForm and store it inside an instance variable inside SecondForm like this:
public partial class SecondForm : Form
{
MainForm form1 = null;
public SecondForm(MainForm main_form)
{
form1 = main_form;
}
private void calltest()
{
form1.test();
}
...
}
Now when you create your instance of SecondForm, make sure that you inject the original instance of MainForm with something like this:
SecondForm second_form = new SecondForm(main_form); //If you are creating this from MainForm, then simply pass `this` as the construction parameter

Access and modify form listbox from another class

I'm having some issues accessing and modifying a listbox control from another class.
Here's the MainForm, which holds the listbox:
public partial class MainForm : Form
{
private static MainForm mainForm = new MainForm();
internal static MainForm init()
{
return MainForm.mainForm;
}
public MainForm()
{
InitializeComponent();
}
}
And here's the second class that I'm using to attempt to modify the listbox (the items are added from an event):
public class Utils
{
void ItemsReceived(object sender, DataReceivedEventArgs<ListboxItems> e)
{
MainForm.init().listBox1.Items.Add("test");
}
}
Using this code setup, nothing is added to the listbox. Any ideas? Or even a better way to tackle this?

Typically visual studio generates the following code in a Program.cs file:
Application.Run(new MainForm());
If this line still exists, your static mainForm variable will hold a different instance of MainForm than the one visible when running the application. If I'm right, change the line in Program.cs to:
Application.Run(MainForm.init());
On a side note, while using the singleton (anti)pattern, consider changing the name of that method to GetInstance() because init() appears to initialize something.

Accessing main form objects in other .cs files

It's easy to access sub-window's objects from main file because we must create the sub window anyway. So there's something like this:
SubForm subform = new SubForm();
if (subform.ShowDialog() == DialogResult.OK)
{
text = subform.textBox1.Text;
//...
}
But I have some troubles with editing a combobox (placed inside main form) by a sub-cs file. I can't simply create a new main window. I've edited Program.cs file:
static class Program
{
public static MainForm mainform; //main window reference
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(mainform = new MainForm());
}
}
Now I can access the combobox:
Program.mainform.comboCurves.Items.Add("test");
Is it any better solution for this?

You can also pass a reference to your mainform directly into your subform, at least your main form won't be available to your whole application :
MainWindow.cs :
SubForm subform = new SubForm(this);
SubForm.cs :
public partial class SubForm : Form
{
private MainForm mainForm;
public SubForm(MainForm mainForm)
{
InitializeComponent();
this.mainForm = mainForm;
}
}
So now you can access it like mainForm.comboCurves.Items.Add("test");
Also, a better way would be to have your main form inherit form an interface that exposes only the necessary stuff :
public partial class MainForm : Form, IRestrictedInterfaceOfMainForm
{
public void AddStuff(string stuff)
{
comboCurves.Items.Add(stuff);
}
}
public interface IRestrictedInterfaceOfMainForm
{
void AddStuff();
}
public partial class SubForm : Form
{
private IRestrictedInterfaceOfMainFormmainForm mainForm;
public SubForm(IRestrictedInterfaceOfMainFormmainForm mainForm)
{
InitializeComponent();
this.mainForm = mainForm;
}
}
That way you only access what you really need and don't play directly with MainForm's controls. For example, if you want to change comboCurves to an array of textboxes, the second form won't even notice it.
Your solution works, but you should always try to expose the least amount of information, which is partly covered by the Interface segregation principle, from the SOLID principles.

How to call my public class to my main form?

I have this class ClassMainForm and a form named MainForm. I made a method in my class, then inside of that is my codes like quantity1.Show. My question is, how do I call my function from class to my main form? I'd appreciate all your help.
ClassMainForm :
public void Visible()
{
GroupInstruction.Hide(); // <<== how do i call my controls in my MainForm?
quantity1.Show(); // <<== how do i call my controls in my MainForm?
}
Thanks Guys...

First create a new instance of your class:
ClassMainForm cmf = new ClassMainForm();
After this you can use cmf.NAMEOFYOURFUNCTION to call your function.
NAMEOFYOURFUNCTION = One of the methods/functions in your class.
With the cmf. u refer to your class, and after the dot u select the name of your method/function.
EDIT:
Placed a numerupdown on the form, and I called it numerUpDown1.
MAINFORM:
namespace Stack_Overflow_2
{
public partial class MainForm : Form
{
public MainForm()
{
InitializeComponent();
}
public NumericUpDown numericupdown()
{
return numericUpDown1;
}
}
}
CLASS:
namespace Stack_Overflow_2
{
class ClassMainForm
{
MainForm mf = new MainForm();
public void Visible()
{
mf.numericupdown().Show();
}
}
}

C# - Accessing tree view control from another class

I'm working on a Windows Forms application in C# with Visual Studio 2010.
There is a form mainForm.
mainForm contains a tree view control xmlTreeView.
There is a self-written class myClass.cs.
Now, myClass needs to access the xmlTreeView. However I don't know a) how to access the form and b) which way would be best to do that.
I tried to implement an interface following oleksii's answer but I don't get it. The main form of the application is defined like this:
public interface IMainForm {
TreeView treeView { get; }
}
public partial class mainForm : Form, IMainForm {
public TreeView treeViewControl {
get { return myTreeViewControl; }
}
// Some code here
[...]
RuleTree rt = new RuleTree(); //How do I call this with the IMainForm interface???
}
Another class RuleTree is defined like this:
class RuleTree {
private readonly IMainForm mainForm;
public RuleTree(IMainForm mainForm) {
this.mainForm = mainForm;
}
}
How do I call the constructor of RuleTree with the IMainForm interface???

I would do the following. Don't see it as code, it's just so that you can understand, you can modify it accordingly.
public class MyClass
{
public void MyMethod(YourTreeViewControl treeview)
{
// Do what you need to do here
}
}
Then in your forms code behind just instantiate MyClass and pass an instance of your treeview to it, something like this:
MyClass myClass = new MyClass();
myClass.MyMethod(tvYourTreeViewControl);
Hope this makes sense :)

One of the possible approaches would be to use dependency injection here. MyClass would have a constructor that takes a Form parameter. Thus when you create MyClass it would have the form injected. For example:
Foo
{
Foo(){}
}
Bar
{
private Foo currentFoo;
Bar(Foo foo) //dependency injection
{
currentFoo = foo;
}
public void OtherMethod()
{
//do something with currentFoo
}
}
It will be better to use interfaces (or abstract classes), so instead of Foo you could inject IFoo, this largely decouples your classes, which is a good design decision.

I have commented my code please read comments, I can make solution available as well.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
namespace WindowsFormsApplication1
{
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
///
//Declare a static form that will accesible trhought the appication
//create form called frmMain form or any other name
//
public static frmMain MainForm { get; private set; }
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
//comment out default application run
//Application.Run(new MainForm());
//create a new instance of your frmMain form
//inside your main form add a tree view
//Loacte this file "frmMain.Designer.cs"
//Change treeView1 from private to public
// public System.Windows.Forms.TreeView treeView1;
MainForm = new frmMain();
//before I show my form I'll change docking of my tree view from myClass
MyClass mine = new MyClass(); //done
MainForm.ShowDialog();
}
}
public class MyClass
{
public MyClass()
{
Program.MainForm.treeView1.Dock = DockStyle.Fill;
}
}
}

This is not possible to access asp.net server side controls into other class other then their cs class e.g
test.aspx is a page
you can access test page controls only in test.aspx.cs
Other then this class this is not possible.