how to change textbox.text from one child form to other child form. Both are open in MDI form in C#.net

Question

I have one MDI Form, With two Child Form named MDIParent1,Form1,Form2. MDI will Load with showing/loading this two child form in it.

private void MDIParent1_Load(object sender, EventArgs e)

    {
        Form childForm1 = new Form1();
        childForm1.MdiParent = this;
        childForm1.Show();

        Form childForm2 = new Form2();
        childForm2.MdiParent = this;
        childForm2.Show();
    }

In Form1 there is a textbox1 and a Button. And in form2 there is textbox2. So what i am trying to is when I write sometext in Form1's Textbox1 and then Click on Form1's Button, That same text will be write in Form2's Textbox2.

I Tried a lot. But Dosnt get output. the values are passing through one child form to other. but Textbox.text property is not updating.

I tried it Without MDI Form. The Form1 And Form2 will opened independently. and I have to close and reopen Form2 each and every time when i click on Form1's Button. It Works little bit. But I need it in MDI Form. While Both Child Forms were opened in MDI and then I want to Update property of textbox (In short I need to do this form2.textbox.text = Form1.textbox.text where Form1 and Form2 both are Child forms)

Regards, Salil

Answer 1

Try using the the MDI parent (MDIParent1) as a moderator between the 2 forms.
MDIParent1 will register to Form1's events and will modify Form2 respectively.

Modifications for Form1

Add to Form1 a public event notifying that the button was pressed. The event should also contain information about the current text in textBox1. For this, use a class deriving from EventArgs:

The EventArgs:

public class TextChangedArgs:EventArgs
{
    string _text;

    /// <summary>
    /// Gets text .
    /// </summary>
    /// <value>
    /// The text.
    /// </value>
    public string Text
    {
        get { return _text; }
    }

    public TextChangedArgs(string text)
    {
        this._text = text;
    }
}

The Public Event:

public event EventHandler<TextChangedArgs> OnTextChanged;

The Button1 Click Event:

 private void button1_Click(object sender, EventArgs e)
    {
        if (this.OnTextChanged != null)
        {
            this.OnTextChanged(this, new TextChangedArgs(this.textBox1.Text));
        }
    }

Modification to MDIParent1

In the following code, the modification is the registration to the event, and handling it:

 void MDIParent1_Load(object sender, EventArgs e)
    {
        Form1 childForm1 = new Form1();
        childForm1.MdiParent = this;
        childForm1.OnTextChanged += childForm1_OnTextChanged;
        childForm1.Show();

        Form2 childForm2 = new Form2();
        childForm2.MdiParent = this;
        childForm2.Show();
    }

    void childForm1_OnTextChanged(object sender, TextChangedArgs e)
    {
        //just getting the Form 2 instance, you can implement it in any way you choose to (e.g. make it global...)
        Form2 childForm2 = this.MdiChildren.Where(c => c is Form2).FirstOrDefault() as Form2;
        if (childForm2 != null)
        {
            childForm2.SetText(e.Text);
        }

    }

Modifications to Form2

The modification is Adding a public method for setting the text:

 public void SetText(string text)
    {
        this.textbox2.Text = text;
    }

this should work for you...