Windows Forms, getting a property from parent form

Question

I'm having a bit of a problem. I have a datatable in the parent form. I open a dialogbox form that gets the datatable property and creates a checkboxlist. This will be used to export those columns. But when I run the application the parentform property is null. I've tried setting it in the parent and dialogbox form (I assumed this would have been done automagically if ShowDialog() was called).

Can someone take a look and see where I'm going wrong? From the dialogbox:

frmParent MyParentForm = (frmParent)this.ParentForm;
for (int i=0; i<MyParentForm.DataGridTable.Count; i++)
{
   chkListExportItems.Add(MyParentForm.DataGrid.Columns[i].Name,true);
}

From the parent form:

frmExports MyForm = new frmExports();
MyForm.MdiParent = this;
if (MyForm.ShowDialog == DialogResult.OK)
{
   MyForm.SelectedItems // Do something
}

Answer 1

Give a reference to the DataGridTable to your dialogbox form. You may pass it in the constructor. You should avoid using Parent/ParentForm and avoid casting.

Answer 2

1) "MdiParent" is the wrong property to use.

2) Call MyForm.ShowDialog(this);

3) Use "this.Owner" in the modal form.