calling method of parent form in c#

Question

Hi,

i have opened a mainform and call a child form like

     Form4 f = new Form4();
     f.Owner = this;
     f.Show(this);

in form4, user selects a text file, the contents of which are to be displayed in a textBox1 of mainform

i was trying something like Owner.textBox1.Text = "file contents";

but it does'nt work

thanks in advance

apals

Answer 1

You will need to set the "modifiers" to at least public for the properties of the control to be able to have access to it.

Answer 2

The best way to link different forms together is via events. Create an event in Form4 like FileSelected and then do something like this:

Form4 f = new Form4();
f.FileSelected += (owner, args) => {
    textBox1.Text = args.FileName;
};
f.Show(this);

Answer 3

In Form4 you can cast Owner to the correct type:

var o = (Form1) this.Owner;
o.textBox1.Text = "file contents";

For this to work, the owner must be of type Form1 and textBox1 on that type must be a public member or property.

Answer 4

Besides this is really bad design, you need to make textBox1 a public member of your main form and cast f.Owner to the main form type.

Like:

 Form4 f = new Form4();
 f.Owner = this;
 f.Show(this);

 // Inside Form4
 MainForm main = this.Owner as MainForm;
 if (main != null) main.textBox1.Text...

Answer 5

A best practice would be to define yourself a property that would itself set the Text property of your private control. Here's an instance:

public partial class MainForm : Form {
    public string ContentDescription {
        set {
            textBox1.Text = value.trim();
        }
    }
}

Then after, you'll be able to access this property through type-casting to your particular type:

public partial class SecondaryForm : Form {
    public MainForm OwnerForm {
        get {
            return (MainForm)this.Owner;
        }
    }

    public void someMethod() {
        OwnerForm.ContentDescription = "file contents";
    }
}

Remember that in C#, every Control is declared private. So, to access it, the best practice is to define a property that will grant you the required access to it. Making a member public is generally not a good idea, depending on what you're trying to achieve.

EDIT For the parse method, perhaps should you consider making it public or internal so that you may access it through the correctly type-casted Owner property of your child form.

Making a hlper class might be the right solution though, so it is not GUI dependent.

Answer 6

As Andrew already gave the correct solution for event driven, there is also a sync (or blocking) method available:

Form4 f = new Form4;
if(f.ShowDialog() == DialogResult.OK)
{
    textBox1.Text = f.FileName;
}