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C# Geting null value from other form [duplicate]

I have two forms. First one has one textbox.Second one has a devexpress data grid.
I want to achieve that:
first click a button and form2 opens.
if I click a row in the data grid in form2, this value should be shown inside the textbox in form1.(form1 is already opened.)
ı m a beginner. thanks for your help.
Form1 frm1 = new Form1();
frm1.textBox1.Text = gridView1.GetFocusedRowCellValue("ID").ToString();
frm1.Show();
when I do that, a new form opens. I dont want to open a new form. Form1 is already opened. I want to add values to its textbox.

Pass form1 as a reference to form2:
In your button click handler on form 1 to open form 2
private void Button_Click(object sender, EventArgs e)
{
Form2 frm2 = new Form2(this);
frm2.Show();
}
form2 code
private Form1 frm1;
// constructor (pass frm1 as reference)
public Form2(Form1 frm1) {
this.frm1 = frm1;
}
//put this in your event handler for a row click in the grid
frm1.textBox1.Text = gridView1.GetFocusedRowCellValue("ID").ToString();

you can try something like this.
When you click on frm1.SimpleButton this function will be called a show your Form2. On Form2 you have to set InnerProperty (from your datagrid?) a when you close Form2 you can use this property.
private void SimpleButton_Click(object sender, EventArgs e)
{
using (Form2 frm = new Form2())
{
frm.InnerProperty = "default text";
DialogResult result = frm.ShowDialog();
SimpleButton.Text = frm.InnerProperty;
}
}

Finally, I solved the problem.
Application.OpenForms["form1"].Controls["textBox1"].Text =
gridView1.GetFocusedRowCellValue("ID").ToString();
Thanks for help.

How to update UI from one form to another form

I have Form1 which contains a combobox which show some number saved in Database and it also contain a button(butn2) which on click popups a another form and another button(butn1) which updates the combo from database.
Here on this form (Form2, Child form of some sort)i try to updat the data of the combobox of previous form(parent one) on button click by creating object of Form1
But when i open and see the combobox it still show the same data(it is not updated).
Is it possible to update the UI from combobox from one form to another ? My code is
Form1 code:
public Form1()
{
InitializeComponent();
}
Form1.Designer.cs:
Button butn1;
Button butn2;
ComboBox cmb1;
private void InitializeComponent()
{
cmb1 = new ComboBox();
butn1 = new Button();
}
this.butn1.Click += new System.EventHandler(this.button_Save_Click);
this.butn2.Click += new System.EventHandler(this.button_Save_Click2);
public void button_Save_Click(object sender, System.EventArgs e)
{
UpdateComboBoxFromMySQL.InsertdataInCombo(this.cmb1 ); //Here i add data in combox through database, the code is correct i verfied it
}
public void button_Save_Click2(object sender, System.EventArgs e)
{
Form2 frm2 = new Form2();
frm2.show();
}
Form2 code:
Button butn2 = new Button();
//first i add some data to database, which are added i have seen the table-columns by opening DB. Now i want to update the Combobox from that data
Form1 obj1 = new Form();
this.butn2.Click += new System.EventHandler(obj1 .button_Save_Click); //It calls the function button_Save_Click, i saw on debugging but still it do not update the data.
How to update this combobox of Form1 from Form2 button click?

You also can show form2 with parent form1
public void button_Save_Click2(object sender, System.EventArgs e)
{
Form2 frm2 = new Form2();
frm2.Show(this);
}
Then you can access to form1 through the Owner property of form2.
this.butn2.Click += new System.EventHandler(Owner.button_Save_Click);

Let's suppose that the name of your first Form is Foobar. In that case, instead of
Form1 obj1 = new Form();
this.butn2.Click += new System.EventHandler(obj1 .button_Save_Click);
which creates a new Form object, you need this:
Form obj1 = null;
for (int i = ((obj1 == null) && (Application.OpenForms.Count - 1)); i >= 0; i--)
{
if (Application.OpenForms[i].Name == "Foobar")
obj1 = Application.OpenForms[i];
}
if (obj1 != null)
{
this.butn2.Click += new System.EventHandler(obj1 .button_Save_Click);
}
Explanation: obj1 is initialized with null. A cycle is created to find the Form you want to find, the end sign being either completed iteration or the Form being found. If the Form is found, then obj1 is initialized. After the cycle, if obj1 was initialized, then you can use it, its members and methods, including, but not limited to button_Save_Click.

Switching between forms and sending variable correctly

I am wondering how can I correctly switch between forms by button click event.
I have Form1 and Form2.
Form1 have: -TextBoxForm1
-ButtonForm1
Form2 have: -TextBoxForm2
-ButtonForm2
I would like to on_click ButtonForm1 event go to the Form2. Then I want to write some message to TextBoxForm2 and press ButtonForm2 it will go to the Form1 again and message from TextBoxForm2 will appear in TextBoxForm1.
Everything works fine, but I have one problem. When I close application and I wanna debug and start it again, some errors appear like:"application is already running".
Form1:
public static string MSG;
public Form1()
{
InitializeComponent();
TextBoxForm1.Text = MSG;
}
private void ButtonForm1_Click(object sender, EventArgs e)
{
Form2 form2 = new Form2();
this.Hide();
//There is probably my fault but when I was trying this.Close(); everything shutted down
form2.Show();
}
Form2:
private void ButtonForm2_Click(object sender, EventArgs e)
{
Form1.MSG = TextBoxForm2.Text;
Form1 form= new Form1();
form.Show();
this.Close();
}
How can I do this correctly please? :) I am beginner, thank you!

I would not go the route of using a STATIC for passing between forms as you mention you are a beginner, but lets get the closing to work for you.
In your main form create a new method to handle an event call as Hans mentioned in the comment. Then, once you create your second form, attach to its closing event to force form 1 to just become visible again.
// Inside your Form1's class..
void ReShowThisForm( object sender, CancelEventArgs e)
{
// since this will be done AFTER the 2nd form's click event, we can pull it
// into your form1's still active textbox control without recreating the form
TextBoxForm1.Text = MSG;
this.Show();
}
and where you are creating form2
private void ButtonForm1_Click(object sender, EventArgs e)
{
Form2 form2 = new Form2();
form2.Closing += ReShowThisForm;
this.Hide();
form2.Show();
}
and in your second form click, you should only need to set the static field and close the form
private void ButtonForm2_Click(object sender, EventArgs e)
{
Form1.MSG = TextBoxForm2.Text;
this.Close();
}

Easy solution is to use modal form. Display Form2 temporarily, when it is displayed Form1 is invisible.
var form2 = new Form2();
this.Visible = false; // or Hide();
form2.ShowDialog(this);
this.Visible = true;
And to pass data you can define property in Form2, to example:
public string SomeData {get; set;}
Form1 has to set SomeData, which you take in Shown and display. Same property can be used to get data from Form2 (before closing).
// form 1 click
var form2 = new Form2() { SomeData = TextBoxForm1.Text; }
this.Visible = false;
form2.ShowDialog(this);
this.Visible = true;
TextBoxForm1.Text = form2.SomeData;
// form 2 shown
TextBoxForm2.Text = SomeData;
// form 2 click
SomeData = TextBoxForm2.Text;
Close();

Adding panels from Form2 to form1(MainForm)

ok, I have 2 forms...On f1 is a flowlayoutPanel and a button that opens f2.
On f2 there are small panels, each is a diffrent color.
I want to do this:when I click on a panel from f2 a panel is created in FLP in f1 that has the same color and size. The problem is that when I click on the first panel on f2 nothing happens.
this is what I have so far:
f1
private void Add_Color_Click(object sender, EventArgs e)
{
Form2 f2 = new Form2();
f2.Show();
}
f2
Form1 f1 = new Form1();
private void panel1_Click(object sender, EventArgs e)
{
Panel pnl = new Panel();
pnl.BackColor = panel1.BackColor;
pnl.Size = panel1.Size;
f1.BackColor = panel1.BackColor;
f1.FLPMain.Controls.Add(pnl);
this.Close();
}

So your child form shouldn't need to know a thing about your first form. It sounds like you're creating something like a generic color picker tool. You should be able to use that same form somewhere else in your application where you need to pick a color as well, for example.
As a general rule it's best if a child form doesn't "know" about it's parent, it keep them decoupled, makes it easier to write each class separately without forcing the developer to be so knowledgeable about the other types in the project. It's actually not terribly hard.
So rather than having Form2 go and add a panel to Form1, it can just notify Form1 when it's chosen a color and a size. This is done through an event:
public class Form2 : Form
{
//define the event
public event Action<Color, Size> ColorChosen;
private void panel1_Click(object sender, EventArgs e)
{
//raise the event
var panel = (Panel)sender;
ColorChosen(panel.BackColor, panel.Size);
Close();
}
}
(Size note; by using sender here this same event handler can be added to all of the panels you want to be clickable, rather than having a ton of event handlers that do almost the same thing.)
Then on Form1 we just assign an event handler to this custom event where we create and add a new panel to the form:
Form2 child = new Form2();
child.ColorChosen += (color, size) =>
{
Panel panel = new Panel();
panel.BackColor = color;
panel.Size = size;
Controls.Add(panel);
};
child.Show();

You're creating a new instance of Form1 here:
Form1 f1 = new Form1();
But you want to add your panels on the existing one, so use:
Form f1 = Application.OpenForms['formname'];

Just do it this way
private void Add_Color_Click(object sender, EventArgs e)
{
Form2 f2 = new Form2(this);
f2.Show();
}
class Form2
{
private Form1 _frm;
public Form2(Form1 frm)
{
//initialize + other code if required
_frm = frm;
}
private void Panel_Click(object sender, EventArgs e)
{
_frm.CreatePanel(/*param you need*/); //name it what ever you want
}
}
bassicaly something like that should do the job
/e there might be some typos but the idea is there

Writing from textbox in Form2 to Datagridview in Form1

I am still new to C# so please bear with me.
I have Form1 with a DataGridView and a Button. This button opens Form2.
Form2 contains a TextBox and a Button that closes Form2.
I need to write the text from the TextBox in Form2 into the first cell of the DataGridView in Form1. In the application I am developing, there is other data already in the DataGridView in Form1.
I have uploaded the Visual Studio 2010 file here.
EDIT:
Please look at this screenshot:
Here is the code I'm using:
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form1 form1 = new Form1();
form1.dataGridView1.Rows[0].Cells[0].Value = textBox1.Text;
this.Close();
}
}
I seem to instantiating a new Form1 when I don't want to.
Appreciate the help.

You don't need Form2 to instantiate (again) the main form (Form1).
A more appropriate approach is to open the auxiliary form containing the text-box as a modal-dialog window, and let the opener form (Form1) access the text entered by the user at Form2 instance.
Here below are described the changes needed:
Form2 changes:
1.- Add a new class member to store the string that is to be introduced in the text-box textBox1.
public String textFromTextBox = null;
2.- Add code to your OK button's clic event-handler, so that you store in the new class member textFromTextBox the value introduced in the text-box:
3.- Last, in the same clic event-handling code set the DialogResult property to DialogResult.OK.
The Form2 code would look like this:
public partial class Form2 : Form
{
[...]
// This class member will store the string value
// the user enters in the text-box
public String textFromTextBox = null;
[...]
// This is the event-handling code that you must place for
// the OK button.
private void button1_Click(object sender, EventArgs e)
{
this.textFromTextBox = this.textBox1.Text;
this.DialogResult = DialogResult.OK;
}
}
Form1 changes
1.- In your button with the label "Enter Text" (that is actually missing in your code), in the Click event-handler put the code necessary to open the Form2 as a modal Dialog.
2.- Set the cell value in your data-grid accordingly by recovering the value stored in the Form2's textFromTextBox member.
3.- Finally dispose your Form2 instance.
Form2 myFormWithATextBox = new Form2();
if (myFormWithATextBox.ShowDialog(this) == DialogResult.OK)
{
this.dataGridView1.Rows[0].Cells[0].Value = myFormWithATextBox.textFromTextBox;
}
myFormWithATextBox.Dispose();
Take into account that your main form is Form1 while Form2 it is just an auxiliary form control, it should not take much control on the flow of your application, and therefore not assume the responsibility of instantiating the main form.

You can pass variable from Form to another by create another contractor that accept parameters as the following:-
1) go to form1 then create another contractor:
public Form1(string myString)
{
InitializeComponent();
if (myString != null)
dataGridView1.Rows[0].Cells[0].Value = myString;
}
2) go to form2 and under the button write this code:
private void button1_Click(object sender, EventArgs e)
{
Form1 frm1 = new Form1(textBox1.Text);
frm1.ShowDialog();
}
Here you are your application after modification