There is another question that is very similar to mine however after reading it i still cannot get it to work.
I have two forms , MainForm and SecondForm and a few other classes, i need an instance of my AVLtree and be able to access it through my other forms.
This is what ive done so far
MainForm
public partial class MainForm : Form
{
AddArtist secondForm = new AddArtist();
public static AVLTree<Artist> treeAVL { get; set; }
public MainForm()
{
InitializeComponent();
}
private void butAdd_Click(object sender, EventArgs e)
{
secondForm.Show();
}
private void MainForm_Load(object sender, EventArgs e)
{
}
}
}
SecondForm
public partial class AddArtist : Form
{
String Name1 = "No Name";
int Members = 0;
public AVLTreetreeAVL = new AVLTree();
public AddArtist()
{
InitializeComponent();
treeAVL = MainForm.treeAVL;
}
private void MainForm_Load(object sender, EventArgs e)
{
}
private void butAdd_Click(object sender, EventArgs e)
{
Name1 = tBName.Text;
Members = (Convert.ToInt32(tBMem.Text));
Artist newArtist = new Artist(Name1,Members);
try
{
treeAVL.InsertItem(newArtist);
}
catch (Exception )
{
MessageBox.Show("No Data Entered", "Error",MessageBoxButtons.OK, MessageBoxIcon.Error);
}
tBName.Text = "";
tBMem.Text = " ";
}
}
}
Any help would be greatly appreciated pointing out where im going wrong or how to solve it.
It now compiles however it gives an error of Object reference not set to an instance of an object. i hope ive gone about coding this is the right way.
What is the access modifier of AVLTree class? Check if it is private or internal, since your code needs it to be public.
Set public on your parametrized type
public class Artist
{
..
}
Related
So I'm making this small program for my assignment at university and I'm finding it hard to add to my list in my form. Here is my code:
public partial class WorkOutBeam : Form
{
Check checkLib;
public BindingList<ListBox> list;
public WorkOutBeam()
{
InitializeComponent();
}
public void StartForm(object sender, EventArgs e)
{
list = new BindingList<ListBox>();
listBox1.DataSource = list;
}
private void NewForce_Click(object sender, EventArgs e)
{
NewForceName forceItem = new NewForceName();
forceItem.Show();
}
public void AddToForceList(string name)
{
list.Items.Add(name);
}
}
NewForceName class below:
public partial class NewForceName : Form
{
public WorkOutBeam workOutBeam;
public NewForceName()
{
InitializeComponent();
}
private void OkButton_Click(object sender, EventArgs e)
{
if (NewForceNames.Text != "")
{
ReferToLibs();
workOutBeam.AddToForceList(NewForceNames.Text);
Close();
}
}
private void ReferToLibs()
{
workOutBeam = new WorkOutBeam();
}
private void NewForceName_Load(object sender, EventArgs e)
{
}
}
So I say to my program, "give me a new force." When it does, it initializes a new form of "NewForceName." I type into a text box and click 'Ok', this starts a public method shown below:
The list is a binding list which refers to the listBox as a data source. However the program tells me that the Items part is inaccessible due to its protection but I don't know how to add it as public. I tried looking in the properties of my listBox but to no avail.
Give this a shot:
public partial class WorkOutBeam : Form
{
Check checkLib;
// public BindingList<ListBox> list; // get rid of this for now
public WorkOutBeam()
{
InitializeComponent();
}
/*public void StartForm(object sender, EventArgs e)
{
list = new BindingList<ListBox>();
listBox1.DataSource = list;
}*/
private void NewForce_Click(object sender, EventArgs e)
{
NewForceName forceItem = new NewForceName(this); // pass a reference to this
// instance of WorkoutBeam
forceItem.Show();
}
public void AddToForceList(string name)
{
// we should do some more things here, but let's keep it simple for now
listBox1.Items.Add(name);
}
}
And
public partial class NewForceName : Form
{
public WorkOutBeam workOutBeam;
public NewForceName( WorkoutBeam beam ) // we take a WorkoutBeam instance as CTOR param!
{
InitializeComponent();
workoutBeam = beam;
}
private void OkButton_Click(object sender, EventArgs e)
{
if (!string.IsNullOrEmpty(NewForceNames.Text))
{
workOutBeam.AddToForceList(NewForceNames.Text);
Close();
}
}
// DO NOT create new WorkoutBeams every time. Use the original.
/*private void ReferToLibs()
{
workOutBeam = new WorkOutBeam();
}*/
}
Disclaimer: I did not address each and every problem in this code. This is just enough so that it should "work" as intended.
how do I access form1 string variable from a different class?
public partial class Form1: Form
{
public Form1()
{
InitializeComponent();
}
public string deva = "123";
//button
private void button8_Click(object sender, EventArgs e)
{
deva = "456";
}
private void button9_Click(object sender, EventArgs e)
{
Other ks = new Other();
ks.test_me();
}
}
public class Other: Form1
{
//trying to access Form1 variable.
public void test_me()
{
Form1 fm = new Form1();
MessageBox.Show(fm.deva);
//deva is 123 but not 456.
//I clicked on button and values changes it form1 however from here it assigns just default value
}
//
//Does creating a new form1 will reset its values?
//Somebody please help me. how to solve this issue.
}
public partial class Form1: Form {
public Form1()
{
InitializeComponent();
}
public string deva = "123";
//button
private void button8_Click(object sender, EventArgs e)
{
deva = "456";
}
private void button9_Click(object sender, EventArgs e)
{
Other ks = new Other(this);
ks.test_me();
}
}
no need to inherit from form1, please pass the object via constructor
public class Other {
Form1 obj = null;
public Other(Form1 object)
{
this obj = object;
}
public void test_me()
{
MessageBox.Show(obj.deva);
}
}
Make your variable deva Static. Access it with Class directly not object.
public static string deva = "123";
public void test_me()
{
//Form1 fm = new Form1();
MessageBox.Show(Form1.deva);
}
Answer on the title question.
Read Jon Skeet's comment for explanation of reason why your approach not workiing.
If you want have access to the variables of another instance, then you need in someway have reference to that instance
One way pass it in the constructor of Other
public class Other: Form1
{
private readonly Form1 _Form1;
public Other(Form1 form1)
{
_Form1 = form1;
}
public void test_me()
{
MessageBox.Show(_Form1.deva);
}
}
Then where you create new instance of Other pass instance of your Form1 ti the constructor of Other
public class Form1
{
private void button9_Click(object sender, EventArgs e)
{
Other ks = new Other(this);
ks.test_me();
}
}
default value is set a every new instance
if you want to keep last value you make a static property
public static string deva = "123";
I'm beginner in C# and having great difficulty to figure our some issues. So I hope my terminology does not matter. Here is my question. Let's say I have the following code:
namespace WindowsFormsApplication8
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
//code starts
//...
//if(...) {
//...
//string parameter = abc.ToString();
//}
//code ends
}//Form1 ends
private void button1_Click(object sender, EventArgs e)
{
//code here
}
private void button2_Click(object sender, EventArgs e)
{
textBox1.Text = parameter;
button1.Perform();
}
}
}
I have difficulties here.
How can I use the string declared in Form1 called parameter inside button2_Click?
textBox1.Text = parameter; doesn't work.
Use a member variable.
public partial class Form1 : Form
{
private string parameter = null;
public Form1()
{
InitializeComponent();
// ...
parameter = abc.ToString();
}
My program compiles and to me it makes sense.
I want to know how to get 'name' to list in my listbox.
I'm trying to use an array of classes so I can add salesmen. A new class will be created every time a person is to be added.
This way the name is a way of calling all the data in that class.
When I execute the program everything looks like its doing what it's suppose to do but it just lists 'form1' in the list box when i press the list names button
This is what i mean:
Where am I going wrong?
SalesmanClass
namespace WindowsFormsApplication1
{
class SalesmanClass
{
private string name;
public string cNum;
public string Email;
public string address;
public string gArea;
public int tSales;
public string Name
{
get
{
return name;
}
set
{
name = value;
}
}
Form 1
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
Form2 w2;
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
if (w2 == null)
{
w2 = new Form2();
w2.Show();
}
}
private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{
}
private void button2_Click(object sender, EventArgs e)
{
Object names;
names = Name;
listBox1.Items.Add(Name);
}
}
}
Form 2
//form2
namespace WindowsFormsApplication1
public partial class Form2 : Form
{
SalesmanClass[] salesman = new SalesmanClass[] { };
public Form2()
{
InitializeComponent();
}
private void Form2_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text.Trim().Length != 0)
{
for (int i = 0; i > salesman.Length; i++)
{
if (salesman[i] == null)
{
salesman[i].Name = textBox1.Text;
break;
}
}
this.Close();
}
else
{
MessageBox.Show("Please Input a Name");
}
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
}
}
}
In this method:
private void button2_Click(object sender, EventArgs e)
{
Object names;
names = Name; // <--- Using this.Name, i.e. Form.Name, NOT SalesmanClass.Name
listBox1.Items.Add(Name);
}
You have accidentally used the Name property of the Form itself (which naturally is "form1").
You need to have a SalesmanClass object at this point, and use the Name property of that instead.
You don't currently have a list of salesmen in your Form1, so you will need to add one and use that.
Also, if you have a list or array of SalesmanClass objects, you should create a List<string> from them and use that to initialise the listbox, something like:
SalesmanClass[] salesmen = new SalesmanClass[] {};
// ...
List<string> names = new List<string>();
foreach (var salesman in salesmen)
names.Add(salesman.Name);
listBox1.Items.AddRange(names);
You can do this using Linq too, but I don't want to confuse you by introducing that into the mix!
In your button2_Click, you have :
names = Name;
What does this Name belong to ? I suspect it belongs to Form1, that's why it's been displaying "form1". If that's the case, you just need to get your SalesmanClass object and get the Name from it.
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)