Pass value from childform to another childform

Question

I open a childform(form2) from another childform(form1) and set MDI to parent form.

Here is how I open form1 as childform of MainForm from MainForm

public partial class MainForm : Form
{
    public MainForm()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        form1 f1 = new form1();
        f1.MdiParent = this;
        f1.Show();
    }
}

Here is how form2 as another childform of MainForm from form1 which is also a childform of MainForm

public partial class form1 : Form
{
    public form1()
    {
        InitializeComponent();
    }
    private void button1_Click(object sender, EventArgs e)
    {
        form2 f2 = new form2();
        f2.MdiParent = this.ParentForm;
        f2.Show();
    }
}

How I will pass a value to form2 from form1? I tried what I am doing to pass a value to modal form but did not works

form1

public partial class form1 : Form
{
    public form1()
    {
        InitializeComponent();
    }
    private void button1_Click(object sender, EventArgs e)
    {
        form2  = new form2();
        f2.MdiParent = this.ParentForm;
        f2.name = textBox1.Text;
        f2.Show();   
    }
}

form2

public partial class form2 : Form
{
    public form2()
    {
        InitializeComponent();
    }
    private string NAME
    public string name
    {
        get { return NAME; }
        set { NAME = value; textBox1.Text = NAME; }
    }
}

Answer 1

You can set MdiParent, and also call MdiParent

public partial class MainForm : Form // IsMdiContainer = true in Properties
{
    private void button1_Click(object sender, EventArgs e)
    {
        Form1 form1 = new Form1();
        form1.MdiParent = this;
        form1.Show();
    }
}

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        Form2 form2 = new Form2();
        form2.MdiParent = this.MdiParent;
        form2.tb = textBox1.Text;
        form2.Show();
    }
}

public partial class Form2 : Form
{
    private string v;

    public Form2()
    {
        InitializeComponent();
    }

    public string tb
    {
        get { return textBox1.Text; }
        set { v = value; textBox1.Text = v; }
    }
}

Answer 2

I think the main problem is the event handler you're using for the button1 click Form1 because you posted two event handlers for button1 in Form1 but i tried this and it worked. Put it in the event handler for button1 click in Form1

private void button1_Click(object sender, EventArgs e)
{
    //Create a new Instance of Form2
    Form2 f2 = new Form2();
    //Sets the MDI Property
    f2.MdiParent = this.ParentForm;
    //Shows the Form
    f2.Show();
    //Open the already created instance
    Form2 f = (Form2)Application.OpenForms["Form2"];
    //Update the Property
    f.name = textBox1.Text;
}

Answer 3

When I pass values from one form to an other I usually create a parameter object

public class FormParams
{
     public string Name {get; set;}
}

In the form that will receive the paramater

public class Form2
{
   public FormParams Parameters {get; set;}
   ...
}

In the form that will make the call you would do something like

FormParams frmParams = new FormParams();
frmParams.Name = "KarlX"

Form2 form = new Form2();
form.Parameters = frmParams;
form.MdiParent = this;
form.Show();

When you want to use the value passed to the form just use

txtStackOverFlowName.Text = Parameters.Name;

Answer 4

This worked for me, you didn't have constructors with InitializeComponent calls and your second code posting didn't have the assign to call.

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        Form2 form2 = new Form2();
        form2.MdiParent = this;
        form2.tb = textBox1.Text;
        form2.Show();
    }
}

public partial class Form2 : Form
{
    private string v;

    public Form2()
    {
        InitializeComponent();
    }

    public string tb
    {
        get { return textBox1.Text; }
        set { v = value; textBox1.Text = v; }
    }
}