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C#: Trying to use control elements in different class - "object reference is required"

I am brand new to C# (I apologise if my question is noobish - I'm teaching myself, so it's a bumpy process). I am trying to develop a winform and since some of the methods are pretty long, I am trying to keep it in a couple classes. This is what I'm kind of hoping to achieve:
public partial class formMainForm : Form
{
public formMainForm()
{
InitializeComponent();
}
private void UpDown1_ValueChanged(object sender, EventArgs e)
{
longCalculations.LongMethod1();
}
}
public class longCalculations
{
private void LongMethod1()
{
// Arbitrarily long code goes here
}
}
I'm doing this in an attempt to keep the formMainForm class tidy and be able to split any calculations into manageable chunks. However, I'm encountering problems with using form controls (e.g. check boxes, numeric up-down controls, etc.) in my non-form classes.
If I leave them as is (e.g. CheckBox1) I get a the name does not exist in the current context error. I searched around and I found that it's because that box is defined in a different class. However, if I change it to formMainForm.CheckBox1, the error is now an object reference is required for the non-static field, method or property. Again, I looked around and it appears that that is due to the form initialization method not being static.
If I change public formMainForm() to static formMainForm(), the error now moves to InitializeComponent(); and I do not know where to go from here. I also tried making an instantiation of the formMainForm() method, but that didn't do anything (the code I attempted to use is below. I found it somewhere on this site as an answer to a similar problem).
private void formLoader(object sender, EventArgs e)
{
shadowrunMainForm runForm = new shadowrunMainForm();
runForm.Show();
}
How can I use the formcontrol names in other classes?
P.S. It is my first post here - I am super sorry if I have missed this question already being asked somewhere. I did search, but I didn't find what I was looking for.
EDIT
It seems I hadn't made myself clear - this was just an example of code and my problem is with the second class, not the first one. I have now simplified the code to:
public partial class formMainForm : Form
{
public formMainForm()
{
InitializeComponent();
}
}
public class longCalculations
{
private void LongMethod1()
{
List<CheckBox> listOfBoxes = new List<CheckBox>();
listOfBoxes.Add(CheckBox1);
// The code displays an "object reference is required for the non-static field, method or property" error at this stage. Changing the "CheckBox1" to formMainForm.CheckBox1 doesn't help
// Arbitrarily long code goes here
}
}
LongMethod1 works perfectly fine when placed in the formMainForm partial class. Moving it to the other form makes it unable to take data from those checkboxes.

I believe this line longCalculations.LongMethod1(); is throwing error cause you are trying to access a instance method as if it's a static method and as well it's defined as private method which won't be accessible outside the class. You need to create an instance of longCalculations class before accessing any of it's member or method(s) and mark the method public like
private void UpDown1_ValueChanged(object sender, EventArgs e)
{
longCalculations ln = new longCalculations();
ln.LongMethod1();
}
public class longCalculations
{
public void LongMethod1()
{
// Arbitrarily long code goes here
}
}
(OR) If you really want it to be a static method then define accordingly with static modifier like
public class longCalculations
{
public static void LongMethod1()
{
// Arbitrarily long code goes here
}
}
Now you can call it like the way you are trying

public static class longCalculations
{
public static void LongMethod1()
{
// Arbitrarily long code goes here
}
}
If you're going to make a call longCalculations.LongMethod1();, then you need to make your class static as such.
Or you leave it as not static method by calling
longCalculations lc = new longCalculations()
lc.LongMethod1();
As for accessing controls in separate classes, you can pass in the form and make the controls public which can be dangerous.
So on your Form.designer.cs, change any control you may have to public modifier. Then you would make a call like this...
private void UpDown1_ValueChanged(object sender, EventArgs e)
{
longCalculations.LongMethod1(this);
}
public void LongMethod1(Form1 form)
{
// Arbitrarily long code goes here
form.label1.Text = someString;
//more settings and whatnot
}
Or do something like this:
public class longCalculations
{
public string LongMethod1()
{
// Arbitrarily long code goes here
return myString;
}
}
longCalculations lc = new longCalculations()
string result = lc.LongMethod1();
this.label1.Text = result;

Ideally, your longCalculations class would not attempt to modify the form directly. Instead it would return an object that the form could use to update its controls.
If you need to access the form directly from the longCalculations class, first change the method to accept an instance of your form
public void LongMethod1(formMainForm myForm)
Then you can pass the form itself as a parameter
var calc = new longCalculations();
calc.LongMethod1(this);

In your other class, you need to have an instance of your formMainForm class:
var myForm = new formMainForm();
Then you can access its members like this:
myForm.CheckBox1.Checked = true;

access textbox from external class - get no errors

I have a project, designed with Visual Community 2015, based on Windows.Form.
I want to realized a simple Server program - using the msdn library:
https://msdn.microsoft.com/en-us/library/fx6588te%28v=vs.110%29.aspx
So I create a simple Form1 with the designer with a richTextbox (name: llog) and one button (click event pushthebutton), which called an external class AsynchronousSocketListener. after this, it should to be to call a methode logme() and a messagebox will pop-up (it works, I see this). But I cannot write into the richTextbox llog. I get no errors, but nothing is written into the box. I can remember, that it has something to do with the invoke or delegate problem. but I cant figure it out. I stuck here since 5 hours with no solution. Can anybody help me - what I have to do, to access the the box from the AsynchronousSocketListener() class? I dont know, why I get no errors!
You see my last attempt - I also try to parse the form as parameter on each methode call (nothing works) - but I cant believe, thats the right way...
ps: bad english, I know ...
// Form1.cs - I reduced it to the min - a window with a textbox and a button appears
namespace MyProject
{
public partial class Form1 : Form {}
public void pushthebutton() {
AsynchronousSocketListener srv = new AsynchronousSocketListener();
srv.StartListening();
}
}
// AsynchronousSocketListener.cs
namespace MyProject
{
public class AsynchronousSocketListener : Form1
{
// Thread signal.
public static ManualResetEvent allDone = new ManualResetEvent(false);
public Form1 form;
public AsynchronousSocketListener()
{
form = new Form1();
logme(this, "constructer");
}
public void logme(Form1 form, string s)
{
MessageBox.Show("inside logme");
if (llog.InvokeRequired)
{
// invoke needed
form.llog.Invoke((MethodInvoker)delegate { llog.AppendText("\r\n" + s); llog.ScrollToCaret(); });
}
else
{
// no invoke needed
llog.AppendText("\r\n" + s);
llog.ScrollToCaret();
}
}
}
}
// inside FormDesigner.cs - shortcut; box is public...
public System.Windows.Forms.RichTextBox llog;

I haven't used winforms in forever, so I don't know whether or not this is a good practice, but in AsynchronousSocketListener, all you're doing is instantiating a new form that is not tied to anything. You might want to actually pass your form into there
public AsynchronousSocketListener(Form1 parent)
{
form = parent;
logme(this, "constructer");
}
and in Form1
AsynchronousSocketListener srv = new AsynchronousSocketListener(this);
On a side note, I don't understand why AsynchronousSocketListener is inheriting from Form1 as seen in the line public class AsynchronousSocketListener : Form1 that doesn't seem to be accomplishing anything

Opening new Windows Form from another Form

Now before anyone goes and marks this question as a duplicate, I'd like to say that my problem differs from the other ones. I'm trying to open an existing Form from another, but I'm having problems in the sense that I've set some Forms to 'host' others (To transfer variables between them). Here's what I mean:
public partial class Schedule_Tasks : Form
{
readonly Schedules schedules;
public Schedule_Tasks(Schedules host)
{
this.schedules = host;
InitializeComponent();
}
So in this snippet of code, I'm trying to get the value of some variables from the Schedules form, into the Schedule_Tasks Form. So I've used the 'host' system. SO far this method works fine, but my problem occurs when I try to open a specific Form, from another that isn't 'hosting'. For example using:
new Schedules().Show();
So obviously when I'm declaring this, I'd put something like 'this' in the brackets after Schedules, but that doesn't work if the Form is being called outside of the 'host' Form. I'd just like to now is there something I'm missing or can change? Please let me know if any part isn't clear, it's a little difficult to explain. Any help is appreciated, Cheers.
EDIT
Here's the code that I'm working with now:
public partial class Schedual_Tasks : Form
{
readonly Scheduals scheduals;
public string selectedDevice;
public string getPath;
public string totalPath;
public Schedual_Tasks(Scheduals host)
{
this.scheduals = host;
InitializeComponent();
selectedDevice = scheduals.itemSelected;
}
private void Schedual_Tasks_Load(object sender, EventArgs e)
{
}
private void changeDirectory_Click(object sender, EventArgs e)
{
new Folder_Browser(this).Show(); //Error Occurs here
}
}
And here is the constructor for Folder_Browser, which is the Form I'm trying to call:
readonly Back_up_Options backOptions;
public string deviceSel;
public Folder_Browser(Back_up_Options host)
{
InitializeComponent();
this.backOptions = host;
deviceSel = backOptions.deviceSel;
}

Your (Folder_Browser) Form's constructor is declared as
public Folder_Browser(Back_up_Options host)
That means you cannot pass a Schedual_Tasks instance as the host parameter because there is no way to convert from a Schedual_Tasks object into a Back_up_Options object. The compiler detects this and creates an error message.
If you cannot pass the host parameter, you can pass null instead:
new Folder_Browser(null).Show();
But then you need to make sure that you check the backOptions member for null reference each time you use it. For example:
if(backOptions != null)
{
deviceSel = backOptions.deviceSel;
}
else
{
deviceSel = null;
}
That in turn means that you will need to check deviceSel for null each time you use it and so on.
And of course, using your Form without a "host" needs to be possible at all. If you have code that requires a "host", it will fail.

WinForm and Class interaction

I have two classess and a Userform. I am trying not to use any Form related code in my classess but i am rather new to OOP. In the CreateGraph() method, i would like to prompt the user with a Yes/No dialog. The code in the method would continue based on the result. I have read some examples on MVP but not exactly sure how i can implement in this case.
Can someone guide me on this? I do believe there is some serious design issues in my code
//singleton class
public class MyApplication
{
private int state;
private static MyApplication instance = null;
public void Task1()
{
GraphGenerator gg = new GraphGenerator();
gg.CreateGraph();
state = 1;
}
public void Task2()
{
//some other tasks..
state = 2;
}
}
Class where i have issue..
public class GraphGenerator
{
public void CreateGraph()
{
//some code for creating a graph..
//here i want to prompt the user with a
// Yes/No dialog box..
}
}
The userform
public partial class Form1 : Form
{
private void btnTask1_Click(object sender, EventArgs e)
{
MyApplication ma = MyApplication.Instance;
ma.Task1();
}
private void btnTask1_Click(object sender, EventArgs e)
{
MyApplication ma = MyApplication.Instance;
ma.Task2();
}
}

Naming - MyApplication - is bad name for controller or presenter, use for example "form name" + "presenter" for naming.
Singleton. Controller or presenter should not be singleton. Inject it through constructor or create in ctor and than save to field or property with private setter in class. For example:
public Form1(FormPresenter presenter)
{
InitializeComponent();
this.presenter = presenter;
}
All other on this simple sample is normal. But for buttons event handlers you can use events in presenter/controller and fire in button event handler specific to presenter/controller events.
Also try to look for MVC/MVP frameworks. Look here for related question:
Implementing MVC with Windows Forms
As I remember there is Microsoft Smart Client Guidance (CAB / Microsoft Composite Application Block) for that.

First , it is best to design your classes as much as possible such that you don't need to intermingle UI code with your domain objects. Can you restructure the code so that the caller/owner of GraphGenerator decides if it needs to ask the user something instead of GraphGenerator doing it? Try to keep GraphGenerator solely focused on his task or making graphs.
Failing that, you could define events (or delegates or callback interface, but lets call these related mechanisms events for now) within GraphGenerator such that the caller/owner can listen for notifications from GraphGenerator and in turn interact with the user. For example, define an event called QueryConfirmSave to raise and the caller can handle the event and prompt the user and then pass back a boolean as an EventArg field.
(The code would be something like this (from the hip, not editor checked):
GraphGenerator gg = new GraphGenerator();
gg.QueryConfirmSave += new EventHandler<ConfirmSaveArgs>(GraphGenerator_QueryConfirmSave);
and then:
private void GraphGenerator_QueryConfirmSave(object sender, ConfirmSaveArgs args)
{
if (MessageBox.Show("Save?") == DialogResult.Yes)
{
args.SaveConfirmed = true;
}
}

You need MessageBox.Show(...).

Updating text box from another class

I'm trying to update a text box from a class called 'hex' to the main form. Within the class 'hex' I have the following code:
Main m = new Main();
m.updateTextBox(convertedHex);
the code passed the variable to the main form to the method called 'updateTextBox' as shown below:
public void updateLog(string input)
{
textBox2.AppendText(input);
}
Sorry if this seems like a silly questions I have been stuck for a while, all the links on my google searches are now purple so I was hoping if someone could explain this to me. Many thanks.

Add this kind of method inside your Main class where textBox is created and call it from outside.
Lets say you added the code in your Program.cs class to start new
// Add this code in Program.cs (or similar where you start the gui
public static readonly Main MainLogWindow = new Main();
// Add this code in Main.cs class
private delegate void NameCallBack(string varText);
public void UpdateTextBox(string input) {
if (InvokeRequired) {
textBox.BeginInvoke(new NameCallBack(UpdateTextBox), new object[] {input});
} else {
textBox.Text = input;
// textBox.Text = textBox.Text + Environment.NewLine + input // This might work as append in next line but haven't tested so not sure
}
}
Call it like: Program.MainLogWindow.UpdateTextBox("test test"); from anywhere assuming that you have MainLogWindow open
This will also allow you to call updates from within other threads.

You have not given us very much information to go on. But as I said in my comment if your startup form is Main, the code that you are showing is creating a new Main Form and any changes made to it will not appear in your UI. You need to pass the form instance to the Hex class constructor. I would do something like this(assuming that the namespaces are the same, they are on the same thread, and your Hex Class is not Static. if on different threads you need to use the Method shown by MadBoy)
public partial class Form1 : Form
{
Hex hex;
public Form1()
{
InitializeComponent();
hex = new Hex(this);
}
}
class Hex
{
Form1 m;
public Hex( Form1 frm)
{
m = frm;
m.updateTextBox("Hello World");
}
}

Your class, presumably a business object, generally shouldn't be concerned with updating the UI. It doesn't particularly need to know that you even have a UI. But there are a couple of different useful approaches you could use.
1) Simply have your UI invoke your business object's method, and let the method return a value, and then the UI can choose to display it.
// inside Main form
var hex = new Hex();
string convertedHex = hex.GetConvertedHex(someArgument);
UpdateTextBox(convertedHex);
2) Have your business object expose an event. The arguments for the event would include whatever string that needs to be broadcast to whomever subscribes to the event. The UI would then be one of the subscribers.
Of the two ideas, I would generally opt for the first unless you actually do need an event model.

jest simple no need to do all of this make text box public from the properties and pass the current form object to the class throudh a method like this
public void mthod(){
//crete a obj of the class
cls1 obj=new clas1();
obj.smethod(this);
}
now in the class can cal it like this
smethod(from1 obj){
obj.textbox.text="";
}