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C# Specific value passing between forms without new instance

I have a C# application that allows the user to log certain events that occur in a game. For simplicity I'll call them ParentForm and ChildForm.
ParentForm is used 99% of the time, to log common events. This is represented as the user clicking a PictureBox and the Tag property of that PictureBox being added to a ListBox. When a "rare" event occurs, the user can click a "log rare event" button on ParentForm to open ChildForm which opens a set of "rare event" PictureBoxes, which function the same as in the ParentForm. The challenge is that I want these common and rare events to be logged to the same ListBox, so I am trying to find out how I would get a PictureBox click (and subsequent Tag from this PictureBox) on the ChildForm to the ListBox on the ParentForm.
The ParentForm does not close while ChildForm is open, and needs to stay open.
In the ParentForm code, I already have the code needed to capture one of the PictureBox clicks and grabbing the Tag, as well as handling dealing with adding it to the ListBox, so it'd be nice if I could just use these.
Here's what I've tried so far for the Parent:
// This file is EventLogger.cs
using rareEvent;
namespace mainWindow {
public partial class EventLogger : Form {
// In the ParentForm (listeners for PictureBox clicks are handled elsewhere)
public void pictureBox_Click(object sender, EventArgs e) {
PictureBox pbSender = (PictureBox) sender;
// Open new window and handle "rare" drops
if (pbSender.Tag.ToString() == "rare") {
// Open rare form
EventLogger.RareForm rare = new EventLogger.RareForm();
rare.Show();
}
}
}
}
and here's the child:
// This file is Rare.cs
using EventLogger;
namespace rareEvent {
public partial class rareEventForm : Form {
// In the ChildForm
private void pictureBox_Click(object sender, EventArgs e) {
// Does not compile if form is not instantiated, but I do not
// want a new instance
EventLogger form;
form.pictureBox_Click(sender, e);
}
}
}
I figured something like this would work, but it gives the error
The type or namespace name 'EventLogger' does not exist in the namespace
'mainWindow' (are you missing an assembly reference?)
Any help would be much appreciated. All the other examples I've found of value passing between forms all seem to create new instances which I don't want or were 8 years old and didn't work.
Appreciate it!
Edit: Code updated to have using <namespace> in each file. The problem still exists of not being able to send values between both forms without using new. (See comment to this answer)

In the first form create an instance (of it) here like my form1. It must be static and all datatypes you want to access should be public.
//FORM1
public partial class Form1 : Form
{
//Instance of this form
public static Form1 instance;
//For testing
public string myProperty = "TEST";
//Assign instance to this either in the constructor on on load like this
public Form1()
{
InitializeComponent();
instance = this;
}
//or
private void Form1_Load(object sender, EventArgs e)
{
//Assign the instance to this class
instance = this;
}
Then in form2 when calling EventLogger.RareForm rare = new EventLogger.RareForm(); instead of new form do
EventLogger.RareForm rare = EventLogger.RareForm.instance
Or in my case
Form1 frm = Form1.instance;
I then check the property of form 1 FROM form2 like so
Console.WriteLine(frm.myProperty);
Output was "Test"
Any trouble shout.

Passing tabConrol properties from on form to another

I am using two forms in a windows form application in C#.I want to pass the tabControl's properties like its "Tabpage count" from first form to second form. Can anyone help me here?I can't create object of first form in second form and call a function beacuse for a new forn object, the tabcontrol gets refreshed.

Inside your first form create an instance of your second Form class as this
Form frm= the instance of your secand form
after that show the instance of your secand form, now you exactly have an instance of your secand form inside your first form and can use all the public properties of it

You can create static public functions exposing desired control properties like in below code.
public static Color TabColor()
{
return Form1.Fom1TabControl1.SelectedTab.ForeColor;
}
and you can access Form1 properties like below;
private void Form2_Load(object sender, EventArgs e)
{
this.Fom2TabControl1.SelectedTab.ForeColor = Form1.ForeColor;
}

First Check your class accessibility and set to public if not work set public static, maybe your namespaces is different
hope it helps

This can be achieved in two ways
Aprroach 1:
Create a public variable in Form2
public int intTabCount=0;
and in Form1, you should call Form2 like
Form2 objForm2 = new Form2();
objForm2.intTabCount = tabPageCountVariable;
objForm2.Show()
Aprroach 2:
Create a parameterized constructor and public variable in Form2
public int intTabCount=0;
public Form2(int TabCounts)
{
intTabCount = TabCounts; // and use intTabCount for your class
}
and call from Form1 like
Form2 objForm2 = new Form2(tabPageCountVariable);
objForm2.Show();
Now if you want to pass value through any events like clicking an button in Form1 which updates anything in Form2, use the below link
Passing Values Between Windows Forms c#

Adding Methods To Windows Form?

I have 2 windows Forms, a parent and a child. The parent is the main form. The child is a dialog where the user can edit their details.
When a button is clicked on the parent form, it loads the child form. Like so:
private void add_account_Click(object sender, EventArgs e)
{
this.account_add_edit = new Form2();
account_add_edit.test();
account_add_edit.ShowDialog();
}
As you can see I've created a new form, tried to call a function from the new form, and then showed the form. The problem is the method from the form is not being called. I am getting an error on the IDE that says Windows.Forms.Form does not contain a method test.
I've created the method in the child form:
public static string test(string val)
{
this.username = val;
}
Any ideas as to what I'm doing wrong?

your method is defined as static , so its not posiible to call it on an instace.
you should eaither not make it static, or call it from as static:
Form2.test();

Use:
Form2.test();
static members are associated directly to the class not to its instances. Than means if you need to access a static member you have to access it using it is container type.
More than that, you can not access normal members from static ones. You can only access staticmembers from their peers.
You cannot do the following inside a static method:
this.Member ...

Passing object to different windows forms

I want to pass a C# object between win forms. At the moment, I have setup a basic project to learn how to do this which consists of two forms - form1 and form2 and a class called class1.cs which contains get and set methods to set a string variable with a value entered in form1. (Form 2 is supposed to get the value stored in the class1 object)
How can I get the string value from the object that was set in form1? Do I need to pass it as a parameter to form2?
Any comments/help will be appeciated!
Thanks,
EDIT: Here's the code I have at the moment: (form1.cs)
private void button1_Click(object sender, EventArgs e)
{
this.Hide();
Form2 form2 = new Form2();
form2.Show();
}
private void button2_Click(object sender, EventArgs e)
{
if (textBox1.Text != "")
{
Class1 class1 = new Class1();
class1.setStringValue(textBox1.Text);
}
}
}
}

There are a few different ways to do this, you could use a static class object, the above example would be ideal for this activity.
public static class MyStaticClass
{
public static string MyStringMessage {get;set;}
}
You don't need to instance the class, just call it
MyStaticClass.MyStringMessage = "Hello World";
Console.WriteLine (MyStaticClass.MyStringMessage);
If you want an instance of the object you can pass the class object that you create on Form1 into Form2 with the following.
private void button1_Click(object sender, EventArgs e)
{
this.Hide();
Form2 form2 = new Form2();
form2.MyClass = class1;
form2.Show();
}
Then create a property on Form2 to accept the class object.
public Class1 MyClass {get;set;}
remember to make the Class1 object a global variable rather than create it within button 2 itself.

Yes, in Form1 you declare an instance of Class1 and then set the parameters as needed, then you pass it to Form2. You could for example have a constructor in Form2 and have a Class1 parameter in it. Assuming that Form1 creates Form2, otherwise you have to have some way for Form1 to find Form2 to pass the instance across.

Since I have been working in ASP.Net the last couple years I have found myself working with Newtonsoft.Json a lot. Turns out to be great within WinForms too, and in this case seemed to simplify passing objects between forms... even complex ones are a breeze!
The implementation is like this:
// Set Object Property within Form
public partial class FlashNotify : Form
{
public string Json { get; set; }
}
On the form load event you can then grab your object:
private void FlashNotify_Load(object sender, EventArgs e)
{
// Deserialize from string back to object
CommUserGroupMessage msg = new CommUserGroupMessage();
msg = Newtonsoft.Json.JsonConvert.DeserializeObject<CommUserGroupMessage>(Json);
}
Lastly is passing the object to the form:
// Serialize the Object into a string to pass
string json = Newtonsoft.Json.JsonConvert.SerializeObject(msg);
FlashNotify fn = new FlashNotify();
fn.Json = json;
fn.Show();
Granted the original selected answer is probably easier, however I like this approach as it avoids the need to replicate the class within your form, which I think makes it easier to maintain (Correction: Miss correctly read the static class in the example, I at first thought it was replicated within the form).

Using Delegate you can easily pass data to a form.
Technically, a delegate is a reference type used to encapsulate a method with a specific signature and return type
Step 1
Add a delegate signature to form1 as below:
public delegate void delPassDataToFrom(Object obj);
Step 2
In form1’s any button click event handler, instantiate form2 class and delegate. Assign a function in form2 to the delegate and call the delegate as below:
private void btnSend_Click(object sender, System.EventArgs e)
{
Form2 frm = new Form2();
delPassDataToFrom del = new delPassDataToFrom(frm.retrieveData);
del(objectToPass);
frm.Show();
}
Step 3
In form2, add a function to which the delegate should point to. This function will use the object passed:
public void retrieveData(Object objPassedFromParent)
{
//use the objPassedFromParent object as needed
}

How to change text in a textbox on another form in Visual C#?

In Visual C# when I click a button, I want to load another form. But before that form loads, I want to fill the textboxes with some text. I tried to put some commands to do this before showing the form, but I get an error saying the textbox is inaccessible due to its protection level.
How can I set the textbox in a form before I show it?
private void button2_Click(object sender, EventArgs e)
{
fixgame changeCards = new fixgame();
changeCards.p1c1val.text = "3";
changeCards.Show();
}

When you create the new form in the button click event handler, you instantiate a new form object and then call its show method.
Once you have the form object you can also call any other methods or properties that are present on that class, including a property that sets the value of the textbox.
So, the code below adds a property to the Form2 class that sets your textbox (where textbox1 is the name of your textbox). I prefer this method method over making the TextBox itself visible by modifying its access modifier because it gives you better encapsulation, ensuring you have control over how the textbox is used.
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public string TextBoxValue
{
get { return textBox1.Text;}
set { textBox1.Text = value;}
}
}
And in the button click event of the first form you can just have code like:
private void button1_Click(object sender, EventArgs e)
{
Form2 form2 = new Form2();
form2.TextBoxValue = "SomeValue";
form2.Show();
}

You can set "Modifiers" property of TextBox control to "Public"

Try this.. :)
Form1 f1 = (Form1)Application.OpenForms["Form1"];
TextBox tb = (TextBox)f1.Controls["TextBox1"];
tb.Text = "Value";

I know this was long time ago, but seems to be a pretty popular subject with many duplicate questions. Now I had a similar situation where I had a class that was called from other classes with many separate threads and I had to update one specific form from all these other threads. So creating a delegate event handler was the answer.
The solution that worked for me:
I created an event in the class I wanted to do the update on another form. (First of course I instantiated the form (called SubAsstToolTipWindow) in the class.)
Then I used this event (ToolTipShow) to create an event handler on the form I wanted to update the label on. Worked like a charm.
I used this description to devise my own code below in the class that does the update:
public static class SubAsstToolTip
{
private static SubAsstToolTipWindow ttip = new SubAsstToolTipWindow();
public delegate void ToolTipShowEventHandler();
public static event ToolTipShowEventHandler ToolTipShow;
public static void Show()
{
// This is a static boolean that I set here but is accessible from the form.
Vars.MyToolTipIsOn = true;
if (ToolTipShow != null)
{
ToolTipShow();
}
}
public static void Hide()
{
// This is a static boolean that I set here but is accessible from the form.
Vars.MyToolTipIsOn = false;
if (ToolTipShow != null)
{
ToolTipShow();
}
}
}
Then the code in my form that was updated:
public partial class SubAsstToolTipWindow : Form
{
public SubAsstToolTipWindow()
{
InitializeComponent();
// Right after initializing create the event handler that
// traps the event in the class
SubAsstToolTip.ToolTipShow += SubAsstToolTip_ToolTipShow;
}
private void SubAsstToolTip_ToolTipShow()
{
if (Vars.MyToolTipIsOn) // This boolean is a static one that I set in the other class.
{
// Call other private method on the form or do whatever
ShowToolTip(Vars.MyToolTipText, Vars.MyToolTipX, Vars.MyToolTipY);
}
else
{
HideToolTip();
}
}
I hope this helps many of you still running into the same situation.

In the designer code-behind file simply change the declaration of the text box from the default:
private System.Windows.Forms.TextBox textBox1;
to:
protected System.Windows.Forms.TextBox textBox1;
The protected keyword is a member access modifier. A protected member is accessible from within the class in which it is declared, and from within any class derived from the class that declared this member (for more info, see this link).

I also had the same doubt, So I searched on internet and found a good way to pass variable values in between forms in C#, It is simple that I expected. It is nothing, but to assign a variable in the first Form and you can access that variable from any form. I have created a video tutorial on 'How to pass values to a form'
Go to the below link to see the Video Tutorial.
Passing Textbox Text to another form in Visual C#

private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2();
TextBox txt = (TextBox)frm.Controls.Find("p1c1val", true)[0];
txt.Text = "foo";
}