call variable from another form c#

Question

I have a DataGridView in Form1 and I\'m using this code to display another form called Generator:

private void button1         


        

Answer 1

A few things are going on here.

1. You have to use the constructor of Generator that take in a form as a parameter.
2. You have to expose the datagridview as a public or internal property on the form that you will pass into Generator.
3. The normal Form class will not know about this property, so you should cast the variable appropriately.
4. You should call the default constructor of Generator when the other constructor is used to make sure everything is initialized correctly. See code sample below.

Something like this should work:

public class Generator
{
    private MyForm myForm;

    public Generator()
    {
        InitializeComponent();
    }

    public Generator(MyForm frm) : this() // DON'T FORGET THIS()
    {
        myForm = frm;
    }

    private void button1_Click(object sender, EventArgs e)
    {
        myForm.MyDataGridView... // Yay, it works!
    }
}

public class MyForm : Form
{
    public MyForm()
    {
        InitializeComponent(); // a datagridview is created here, say "datagridview1"
    }

    public DataGridView MyDataGridView
    {
        get { return datagridview1; }
    }
}

And then in your button click event (which I assume is defined somewhere in MyForm):

private void button1_Click(object sender, EventArgs e)
{
    Form gen = new Generator(this);
    gen.Show();
}

Answer 2

Form 1:

private void button1_Click(object sender, EventArgs e)
{
    Form gen = new Generator(this.mydatagridview);
    gen.Show();
}

Generator Form:

DataGridView _dataGridView;
public Generator(DataGridView dataGridView)
{
    InitializeComponent();
    this._dataGridView = dataGridView;
}

private void button1_Click(object sender, EventArgs e)
{
    this._dataGridView...! // this will work
}

Things that you must do, and know (just tips, you are not forced to do these but I believe you will be a better programmer if you do! ;)

Always call InitializeComponent() in all form constructors. In your sample you didn't call it in one of the constructors.

C# knows only information of the type you have passed. If you pass a Form, then you only get Form properties (i.e. the properties of type Form), not the properties of your own form.

Try to encapsulate things. Do not pass a whole form to another form. Instead, pass things that you would like to use on the other form.

Answer 3

The easiest way from there is to open the designer for the DataGridView (myDataGridView) on Form1 and set the Modifiers property from private to internal or public

This will let you call myForm.myDataGridView from the Generator form.