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Pass Textbox Value From Windows Form To Class

I am learning C# and have run into an interesting issue to me. I have a class variable defined as public and I instantiate a new instance of my form in my class and access the value of the public variable it is always null.
To further explain my issue - this syntax prints the appropriate value
System.Diagnostics.Debug.WriteLine(tboxvalue.ToString());
However, this syntax is always outputting a 0
System.Diagnostics.Debug.WriteLine(f1.tboxvalue.ToString());
How do I need to alter my syntax so that the correct value is passed to the class Functions?
public partial class Form1 : Form
{
public double tboxvalue;
private string exportdata;
public Form1()
{
InitializeComponent();
}
private void btnClicker_Click(object sender, EventArgs e)
{
Functions.EE();
}
private void txtData_CheckedChanged(object sender, EventArgs e)
{
bool #checked = ((CheckBox)sender).Checked;
if (#checked.ToString() == "True")
{
exportdata = "Yes";
tboxvalue = Convert.ToDouble(this.txtData.Text);
System.Diagnostics.Debug.WriteLine(tboxvalue.ToString());
}
else
exportdata = "No";
}
}
class Functions
{
public static void EE()
{
Form1 f1 = new Form1();
System.Diagnostics.Debug.WriteLine(f1.tboxvalue.ToString());
}
}

To access properties of the form, you need to change two Things. First you have to pass the form to the 'EE' method, then you can access the form's properties. Second, don't create a new form in 'EE' method.
public partial class Form1 : Form
{
public double tboxvalue;
private string exportdata;
public Form1()
{
InitializeComponent();
}
private void btnClicker_Click(object sender, EventArgs e)
{
Functions.EE(this);
}
private void txtData_CheckedChanged(object sender, EventArgs e)
{
bool #checked = ((CheckBox)sender).Checked;
if (#checked.ToString() == "True")
{
exportdata = "Yes";
tboxvalue = Convert.ToDouble(this.txtData.Text);
System.Diagnostics.Debug.WriteLine(tboxvalue.ToString());
}
else
exportdata = "No";
}
}
class Functions
{
public static void EE(Form1 f1)
{
System.Diagnostics.Debug.WriteLine(f1.tboxvalue.ToString());
}
}

If i understood your question i guess you are recreated Form1 with own textbox or labels when you click btnClicker button. You can reassign your form objects where you created it.

You might add static Form1 object and Setter routine to Functions class:
private static Form1 _form;
public static void SetForm(Form1 form)
{
_form = form;
}
and pass the form to the class in Form_Load event-click on the form twice:
private void Form1_Load(object sender, EventArgs e)
{
Functions.SetForm(this);
}
Then you can play with the form in Functions class using the object _form
good luck!

Getting the array length from one form class to another form class c#

I initially declare an empty public string array in my program(form1) and when a button is clicked strings in a datagridview cell is put into the array! But I find a difficulty in getting the length of that array to another form class(form2)
public partial class Form1 : Form
{
public string[] strarray;
public string order;
public Form1()
{
InitializeComponent();
}
public void button2_Click(object sender, EventArgs e)
{
var new1=dataGridView2.Rows[0].Cells[2].Value;
ordernew = new1.ToString();
strarray = ordernew.Split(',');
Form2 f2 = new Form2();
f2.Show();
}
}
The assigning string values to the array using split function is successful!
In form2 code is as follows!
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private void Form2_Load(object sender, EventArgs e)
{
Form1 f1 = new Form1();
for (int m = 0; m < f1.strarray.Length; m++)
{
label.Text="Hello";
}
}
}
But when I run the program I get the error "Object reference not set to an instance of an object" at the for loop of form2 ! How can I correct this?

It seems that you are initializing again the Form1.
What you can do is add another property for Form2 then assigned a value it when calling Form2.
In Form2:
public partial class Form2 : Form
{
public string[] strarray { get; set; } //add this.
public Form2()
{
InitializeComponent();
}
private void Form2_Load(object sender, EventArgs e)
{
//You can also use foreach to avoid out of bound index
foreach(var strItem in strarray)
{
label.Text = "Hello " + strItem;
}
}
}
Then when you call it in Form1
public void button2_Click(object sender, EventArgs e)
{
var new1=dataGridView2.Rows[0].Cells[2].Value;
order = new1.ToString();
Form2 f2 = new Form2();
f2.strarry = ordernew.Split(','); //surprise!! I don't know where you get ordernew variable but anyways, assign your values HERE...
f2.Show();
}

Form1 f1 = new Form1();
This is what's causing the problem. you're creating a new window not using the old one, therefore the new window still doesn't have a strarr, the easiest way to solve this with minimal changes is to make Form2 construct takes a Form1 parameter and saves it in a field then use it.
public partial class Form2 : Form
{
private Form1 _form;
public Form2(Form1 form)
{
InitializeComponent();
_form = form;
}
private void Form2_Load(object sender, EventArgs e)
{
for (int m = 0; m < _form.strarray.Length; m++)
{
label.Text="Hello";
}
}
}
And in the event handler of Form1 you'll pass this as parameter:
Form2 f2 = new Form2(this);
f2.Show();
P.S: that's just one way with minimal changes, I don't encourage using it much as it can get confusing on larger scales.

How do I pass data from child of child form to parent form in C#?

I am new to c#. I have the following in my project in windows forms:
Form1 with button and DataGridView.
Form2 with button.
Form3 with button and 3 textBoxes.
As shown in the screenshot In form1, I click buttonOpenForm2 form2 pops up. Then in form2 I click buttonOpenForm3 form3 pops up which has 3 text boxes and button. Now the 3 forms are open.
I enter values in textBox1, textBox2 and textBox3 and when click buttonAddRow ( from form3) I want these values to be inserted into the DataGRidView in Form1.
My question is:
How can I add a row into DataGridView in Form1 ( parent) from form3 (child of child form) WITHOUT closing form2 and form3? I mean I want to pass the data while form2 and form3 are still open.
Please help me. Thank you
Form1:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void buttonOpenForm2 _Click(object sender, EventArgs e)
{
Form2 frm2 = new Form2();
frm2.Show();
}
}
Form2:
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private void buttonOpenForm3 _Click(object sender, EventArgs e)
{
Form3 frm3 = new Form3();
frm3.Show();
}
}
Form3:
public partial class Form3 : Form
{
public Form3()
{
InitializeComponent();
}
private void buttonAddRow _Click(object sender, EventArgs e)
{
//What to write here to insert the 3 textboxes values into DataGridView?
}
}

You cannot expect to get complete code that's ready to be pasted. I quickly wrote this in notepad to give you idea about how events work best in such cases. I assumed Form1 directly opens Form3. Solution below shows how to use events.
You home work is to make it work by adding another form Form2 in between. You can do so by propagating same event via Form2 which sits in middle.
Form3.cs
public partial class Form3 : Form
{
public event EventHandler<AddRecordEventArgs> RecordAdded
public Form3()
{
InitializeComponent();
}
private void buttonAddRow _Click(object sender, EventArgs e)
{
OnRecordAdded();
}
private void OnRecordAdded() {
var handler = RecordAdded;
if(RecordAdded != null) {
RecordAdded.Invoke(this, new AddRecordEventArgs(txtQty.Text, txtDesc.Text, txtPrice.Text))
}
}
}
AddRecordEventArgs.cs
public class AddRecordEventArgs : EventArgs
{
public AddRecordEventArgs(string qty, string desc, string price) {
Quantity = qty;
Description = desc;
Price = price;
}
public int Quantity { get; private set; }
public string Description { get; private set; }
public decimal Price { get; private set; }
}
Form1.cs
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void buttonOpenForm3_Click(object sender, EventArgs e)
{
Form3 frm3 = new Form3();
frm3.RecordAdded += Form3_RecordAdded;
frm3.Show();
}
private void Form3_RecordAdded(object sender, AddRecordEventArgs e) {
// Access e.Quantity, e.Description and e.Price
// and add new row in grid using these values.
}
}

1 Solution
You can use pattern with sending data further by constructor (special setter before Show method) and getting them back after window is closed by public getter.
public partial class Form2 : Form
{
Data Data1 {get; set;}
//Instead of Data you can pass Form1 class as parametr.
//But this might lead to unreadable code, and using too mutch methods and fields that could be private, public
public Form2(Data data)
{
InitializeComponent();
Data1 = data;
}
private void buttonOpenForm3 _Click(object sender, EventArgs e)
{
//Repeat pattern
Form3 frm3 = new Form3(Data1);
frm3.Show();
}
}
Optionally you dont have to call 3rd window constuctor. Just create Instance of third window store it in first form and just Show it by calling first instance you passed with data. But this might be bad practice in larger scale.
2 Solution
You can use singleton pattern. Create Instance of an first form inside constructor of first form and use it in third form. But you would need to ensure that there will be no more then one and always one instance of this object in memory.

You can pass owner to method Show() for new forms. Then you can get owner form from Owner property.
private void buttonOpenForm2 _Click(object sender, EventArgs e)
{
Form2 frm2 = new Form2();
frm2.Show(this);
}
So you can get Form1:
(Form1)frm2.Owner
and call public method of Form1 class and pass there your new data.

if called window is already running then close it and run newly called window

In my app in several time i have to call a window(class). the work of this window is to show the meaning of a word.when i again call that window a new window shows but the previous one also shows.
I have two form named form1,form2.
Form1 is like that:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string a = textBox1.Text;
Form2 s = new Form2(a);// it will be called as many time as i click
s.Show();
}
}
Form2 is like that:
public partial class Form2 : Form
{
public Form2(string s)
{
InitializeComponent();
label1.Text = s;
}
}
what i want is that inside form1 if i call form2 it shows but if i call form2 again the previous form2 window will be closed automatically and new form2 window will be shown instead of previous one.
How can i do that????

Here's an example of storing the Form2 reference at class level, as mentioned by the others already:
public partial class Form1 : Form
{
private Form2 f2 = null;
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
if (f2 != null && !f2.IsDisposed)
{
f2.Dispose();
}
string a = textBox1.Text;
f2 = new Form2(a);
f2.Show();
}
}

I think you should consider using singleton pattern.
You can implement it like this:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string a = textBox1.Text;
Form2.ShowMeaning(a);// it will be called as many time as you click
}
}
and Form2
public partial class Form2 : Form
{
private static readonly Form2 _formInstance = new Form2();
private Form2()
{
InitializeComponent();
}
private void LoadMeaning(string s)
{
label1.Text = s;
}
//Override method to prevent disposing the form when closing.
protected override void OnClosing(CancelEventArgs e)
{
e.Cancel = true;
this.Hide();
}
public static void ShowMeaning(string s)
{
_formInstance.LoadMeaning(s);
_formInstance.Show();
}
}
Hope it helps.

How to access a form control for another form?

I have two Form classes, one of which has a ListBox. I need a setter for the SelectedIndex property of the ListBox, which I want to call from the second Form.
At the moment I am doing the following:
Form 1
public int MyListBoxSelectedIndex
{
set { lsbMyList.SelectedIndex = value; }
}
Form 2
private ControlForm mainForm; // form 1
public AddNewObjForm()
{
InitializeComponent();
mainForm = new ControlForm();
}
public void SomeMethod()
{
mainForm.MyListBoxSelectedIndex = -1;
}
Is this the best way to do this?

Making them Singleton is not a completely bad idea, but personally I would not prefer to do it that way. I'd rather pass the reference of one to another form. Here's an example.
Form1 triggers Form2 to open. Form2 has overloaded constructor which takes calling form as argument and provides its reference to Form2 members. This solves the communication problem. For example I've exposed Label Property as public in Form1 which is modified in Form2.
With this approach you can do communication in different ways.
Download Link for Sample Project
//Your Form1
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2(this);
frm.Show();
}
public string LabelText
{
get { return Lbl.Text; }
set { Lbl.Text = value; }
}
}
//Your Form2
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private Form1 mainForm = null;
public Form2(Form callingForm)
{
mainForm = callingForm as Form1;
InitializeComponent();
}
private void Form2_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
this.mainForm.LabelText = txtMessage.Text;
}
}
(source: ruchitsurati.net)
(source: ruchitsurati.net)

Access the form's controls like this:
formname.controls[Index]
You can cast as appropriate control type, Example:
DataGridView dgv = (DataGridView) formname.Controls[Index];

I usually use the Singleton Design Pattern for something like this http://en.wikipedia.org/wiki/Singleton_pattern . I'll make the main form that the application is running under the singleton, and then create accessors to forms and controls I want to touch in other areas. The other forms can then either get a pointer to the control they want to modify, or the data in the main part of the application they wish to change.
Another approach is to setup events on the different forms for communicating, and use the main form as a hub of sorts to pass the event messages from one form to another within the application.

It's easy, first you can access the other form like this:
(let's say your other form is Form2)
//in Form 1
Form2 F2 = new Form2();
foreach (Control c in F2.Controls)
if(c.Name == "TextBox1")
c.Text = "hello from Form1";
That's it, you just write in TextBox1 in Form2 from Form1.

If ChildForm wants to access the ParentForm
Pass ParentForm instance to the ChildForm constructor.
public partial class ParentForm: Form
{
public ParentForm()
{
InitializeComponent();
}
public string ParentProperty{get;set;}
private void CreateChild()
{
var childForm = new ChildForm(this);
childForm.Show();
}
}
public partial class ChildForm : Form
{
private ParentForm parentForm;
public ChildForm(ParentForm parent)
{
InitializeComponent();
parentForm = parent;
parentForm.ParentProperty = "Value from Child";
}
}

There is one more way, in case you don't want to loop through "ALL" controls like Joe Dabones suggested.
Make a function in Form2 and call it from Form1.
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public void SetIndex(int value)
{
lsbMyList.SelectedIndex = value;
}
}
public partial class Form1 : Form
{
public Form2 frm;
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
frm=new Form2();
frm.Show();
}
private void button1_Click(object sender, EventArgs e)
{
frm.SetIndex(Int.Parse(textBox1.Text));
}
}

Here's also another example that does "Find and Highlight". There's a second form (a modal) that opens and contains a textbox to enter some text and then our program finds and highlights the searched text in the RichTextBox (in the calling form). In order to select the RichTextBox element in the calling form, we can use the .Controls.OfType<T>() method:
private void findHltBtn_Click(object sender, EventArgs e)
{
var StrBox = _callingForm.Controls.OfType<RichTextBox>().First(ctrl => ctrl.Name == "richTextBox1");
StrBox.SelectionBackColor = Color.White;
var SearchStr = findTxtBox.Text;
int SearchStrLoc = StrBox.Find(SearchStr);
StrBox.Select(SearchStrLoc, SearchStr.Length);
StrBox.SelectionBackColor = Color.Yellow;
}
Also in the same class (modal's form), to access the calling form use the technique mentioned in the #CuiousGeek's answer:
public partial class FindHltModalForm : Form
{
private Form2 _callingForm = null;
public FindHltModalForm()
{
InitializeComponent();
}
public FindHltModalForm(Form2 CallingForm)
{
_callingForm = CallingForm;
InitializeComponent();
}
//...