I have an error coming up saying; The name 'map' does not exist in current context. What am I doing wrong?
Sorry I am quite new to coding...
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
variables();
}
public static void variables()
{
string[,] map;
map = new string[140, 140];
}
public static void updateMap(string[,] map)
{
MessageBox.Show("a");
}
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
updateMap(map);
}
}
Create class variable string[,] map.
public partial class Form1 : Form
{
public string[,] map;
...
so your variable "map" will be accessible in all(non-static) methods of this class
Get rid of your variable method.
public static void variables()
{
string[,] map;
map = new string[140, 140];
}
instead, keep it inside your class, so all the other methods may access it.
Think of the class as the parent. All the "methods" inside the class are its children. Everything inside of the children are its "things". Children don't like to share, specially with their brothers or sisters.
That being the case you want it somewhere where the parent has control of it, and the children have to follow the parent's rules of "sharing"
Like this.
public partial class Form1 : Form
{
public string[,] map;
map = new string[140, 140];
public Form 1: Form1()
{
....
}
private void Form1_Load()
{
.....
}
public static void updateMap()
{
.....
}
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
.....
}
}
the variable map is only valid in this method because it is declared within:
public static void variables()
{
string[,] map;
map = new string[140, 140];
}
If it should be valid for the whole class, just declare it as a field:
public partial class Form1 : Form
{
string[,] map;
public Form1()
{
InitializeComponent();
}
...
}
But this is very, very basic. I highly recommend to read a book about C#:
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=c%23
You have only declared map inside the context of the variables method (not sure what this method is even for). As a result, this variable is not accessible anywhere outside of that method. You need to declare it as a class property, like so:
public partial class Form1 : Form
{
private string[,] map;
...
}
Then, initialize this on your Load method:
private void Form1_Load(object sender, EventArgs e)
{
map = new string[140,140];
}
You can then do away with the variables method and reference this property from inside your other methods as you are doing now.
Related
I want a program, which creates a List of Recipes, so something like a management system for Recipes. But I dont know how to access e.g. the List in the other class.
I set every freaking thing public.
public partial class Form1 : Form
{
//default constructor
public static List<Recipe> RecipeList = new List<Recipe>();
}
public partial class Form2
{
//default constructor
private void Form2_Load(object sender, Eventargs e)
{
RecipeList.Add("Chili con Carne");
}
}
public class Recipe
{
//some properties and methods...
{
I cannot access the RecipeList there. How can I reach my goal to get the input for that Recipe in Form2 but then store a List globally where I can e.g. display the List of Recipes anywhere...
u can do like this
public static List<Recipe> RecipeList = new List<Recipe>();
Form1.RecipeList.Add("Chili con Carne");
As your variable public static List<Recipe> RecipeList is static. You can use that variable by using the class name (Form1).
Here is what you can do:
public partial class Form2
{
//default constructor
private void Form2_Load(object sender, Eventargs e)
{
Form1.RecipeList.Add("Chili con Carne");
}
}
I'm trying to call methods from class "Form1" from an other class.
Here's my Code
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
MessageBox.Show("loaded");
orders.ObjectForScripting = new ScriptInterface();
}
private void webBrowser2_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) { }
private void button1_Click_1(object sender, EventArgs e) { }
}
[System.Runtime.InteropServices.ComVisibleAttribute(true)]
public class ScriptInterface
{
public void callMe(string currid)
{
MessageBox.Show(currid);
// the following throws security error
Form1.webBrowser2.Navigate("http://www.mywebpage.com/client/index.php?id="+currid);
}
}
}
INFO: I have 2 WebBorwsers. I'm catching events from webBrowser1 for updating webBrowser2.
My problem is, that i cannot call the webbrowser2 methods outside from Form1.
Any Ideas how i can solve this problem?
Your WebBrowser components are not static (this is a good thing), therefore you cannot refer to them directly off of Form1 as your code sample is attempting to do. You must obtain a reference to a Form1 instance and then you can call methods on them so long as they are marked public. Depending on your needs it is probably even better to just pass along a reference directly to your WebBrowser components
Perhaps something like this:
orders.ObjectForScripting = new ScriptInterface(this.webBrowser2);
...
public class ScriptInterface
{
private WebBrowser _browser;
public ScriptInterface(WebBrowser browser)
{
_browser = browser;
}
public void callMe(string currid)
{
_browser.Navigate("http://www.mywebpage.com/client/index.php?id="+currid);
}
}
Form1 in:
Form1.webBrowser2.Navigate(...)
Is not an object, but it is your type. You need to create an instance of your class, or if you prefer, create an object to be able to call it's method:
Form1 form = new Form1();
form.webBrowser2.Navigate(...)
On top, your method are flagged private, which mean they can only be call from inside your instanced. You should flag them public if you want other object to be able to call them.
public void webBrowser2_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) { ... }
Or if you don't want to create an instance, you can declare this method as being static
public static void webBrowser2_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) { ... }
But you won't be able to access the fields that this class define unless they are static too.
I have Form and Class like that :
namespace ALTER_Control
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
ALTER A = new ALTER();
A.ALTER();
}
}
public class ALTER
{
public Form1 F;
public void ALTER()
{
F.TextBox1.Text="I Altered That";
}
}
}
So i try to call ALTER() to change the textbox1 value in Form1 but i get that error :
object reference not set to an instance of an object
That happens only if i am accessing or modifying the Form1 Controls.
And by the way i set textbox1 modifier to public
So , finally i`d like to change the control value without getting that error.
You need to assign the reference to the form. Like this:
private void button1_Click(object sender, EventArgs e)
{
ALTER A = new ALTER();
A.F = this;
A.ALTER();
}
Why does your ALTER class (which isn't a great class name either) have to know about your form?
private void button1_Click(object sender, EventArgs e)
{
ALTER A = new ALTER();
this.TextBox1.Text = A.ALTER();
}
}
[...]
public class ALTER
{
public String ALTER()
{
// Do your thing
return "I Altered That";
}
}
Use these lines of code:
ALTER A = new ALTER();
A.F = this ;
A.ALTER();
I'm a newbie in c# and visual studio, but not programming in general.
I searched for answer to my question for 3 days and I found plenty of them, but for some weird reason (I'm sure I'm missing something very obvious) I cannot get it to work.
I think it's the most basic question newbies like me ask.
I have a form (Form3) with a text box and a button (I set it up is just for testing purposes).
I want to populate and read this text box from another class. I understand the most proper way to do this is to create a property in Form3.cs with GET and SET accessors. I did that but I cannot get it to work. I'm not getting any error messages, but I'm not able to set the value of the text box either. It just remains blank.
Here's my sample code:
namespace WindowsFormsApplication1
{
public partial class Form3 : Form
{
public string setCodes
{
get { return test1.Text; }
set { test1.Text = value; }
}
public Form3()
{
InitializeComponent();
}
private void Form3_Load(object sender, EventArgs e)
{ }
private void button1_Click(object sender, EventArgs e)
{
a.b();
}
}
public class a
{
public static void b()
{
Form3 v = new Form3();
v.setCodes = "abc123";
}
}
}
Can someone lend me a hand solving this?
The problem is you are setting the value to a new instance of the form. Try something like this:
public partial class Form3 : Form {
public string setCodes
{
get { return test1.Text; }
set { test1.Text = value; }
}
private A a;
public Form3()
{
InitializeComponent();
a = new A(this);
}
private void button1_Click(object sender, EventArgs e)
{
a.b();
}
private void Form3_Load(object sender, EventArgs e)
{
}
}
public class A
{
private Form3 v;
public a(Form3 v)
{
this.v = v;
}
public void b()
{
v.setCodes = "abc123";
}
}
You're creating a brand new Form3() instance.
This does not affect the existing form.
You need to pass the form as a parameter to the method.
Try this:
public partial class Form3 : Form
{
/* Code from question unchanged until `button1_Click` */
private void button1_Click(object sender, EventArgs e)
{
a.b(this);
}
}
public class a
{
public static void b(Form3 form3)
{
form3.setCodes = "abc123";
}
}
This passes the current instance of the form to the other class so that it can update the setCodes property. Previously you were creating a new form instance rather than updating the current form.
Sending form instance to other other class
Form1 objForm1=new Form1();
obj.Validate(objForm1);
Easy way to access controls in another class by modifying Controls Private to Public in the Form(Designer.cs)
Currently have a mainForm.cs which calls a class panel.cs
panel.cs holds multiple pictureboxes with events such as _click, _mousedown, _mouseup
I wish to call a function in mainForm.cs from panel.cs
do i need to use a callback / delegate. Is there another way to access this function
I have tried
Main main = new Main();
main.functioninMain does not work
any help or direction would be appreciated.
for example
panel.cs
private void pb_button1_Click(object sender, EventArgs e)
{
this.BeginInvoke(new Action(main.functioninMain));
}
You should not instantiate another object of MainForm, which creates a duplicate and all the objects withing the new MainForm will not have the values of your actual MainForm.
Approach 1
You can try creating a static instance of you MainForm like below
public partial class MainForm : Form
{
public static MainForm Instance = null;
public MainForm()
{
InitializeComponent();
Instance = this;
}
public SomeMethod()
{
}
}
Now if you have your panel class, then you can easily access public methods and variables of MainClass
class Panel : Form
{
public Panel()
{
MainForm.Instance.SomeMethod();
}
}
Edit: Pass Handle as parameter to the form (From Ben Voigt's suggestion)
Approach 2:
As Ben suggested, it is also important to have a safer code, so much cleaner approach will be passing handle of the control as parameter and then to access them.
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
TestClass test = new TestClass();
test.ModifyText(textBox1);
}
}
public class TestClass
{
public void ModifyText(TextBox textBox)
{
textBox.Text = "New text";
}
}
If we can use delegate & events something like this
public partial class MainForm : Form
{
public MainForm()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Panel formPanel = new Panel();
formPanel.OnPanelClick += new Panel.OnPanelButtonClick(formPanel_OnPanelClick);
formPanel.Show();
}
void formPanel_OnPanelClick(string a)
{
MessageBox.Show(a);
}
}
public partial class Panel : Form
{
public delegate void OnPanelButtonClick(string a);
public event OnPanelButtonClick OnPanelClick = null;
public Panel()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
if (OnPanelClick != null)
{
OnPanelClick("from Panel.cs");
}
}
}
You should avoid circular dependencies at all costs (class A depends on class B, and class B depends on Class A).
There are so many ways to do this, but perhaps one of the easier ways is to use an interface. mainForm.cs implements it like this:
public class mainForm : IMainForm {
// This method is defined in the interface, so mainForm
// must implement it.
public string GetStringFromMainForm() {
return "Hello from MainForm";
}
public void CreatePanel() {
// pass in a reference to myself so panel knows how to
// talk to me.
var panel = new Panel(this);
}
}
And IMainForm (the interface) could look like this:
public interface IMainForm {
string GetStringFromMainForm();
}
Then your panel class can talk to the Main form without having to reference mainForm.cs explicitly:
public class Panel {
// use a private variable to keep track of main form
private IMainForm _mainForm;
// Constructor: pass in a class that implements IMainForm. It isn't
// a type of MainForm, so there's no dependency on the concrete class.
public Panel(IMainForm mainForm) {
_mainForm = mainForm;
}
public void TalkToMainForm() {
var resultFromMainForm = _mainForm.GetStringFromMainForm();
Console.WriteLine(resultFromMainForm);
}
}