Question

So I have two forms. LibraryBookDialog.cs and MainForm.cs. I’m trying to pass an object from LibraryBookDialog.cs to Mainform.cs. Problem is, I get this error when I try to do so…

object reference not set to an instance of the object

Here are my two forms…

LibraryBookDialog.cs:

private LibraryBook book;

public LibraryBook Book
{
    get { return book;}
    set { book = value;} 
}

private void buttonOk_Click(object sender, EventArgs e)
    {
        if (validateData())
        {
            try
            {
                Book.Title = textBoxTitle.Text; 
                Book.Author = textBoxAuthor.Text;
                Book.CopyrightYear = Convert.ToInt32(textBoxCopyrightYear.Text);
                this.DialogResult = DialogResult.OK;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "There was an error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
    }

and MainForm.cs

private void buttonNew_Click(object sender, EventArgs e)
    {
        LibraryBookDialogue dlg = new LibraryBookDialogue();
        dlg.ShowDialog();

        if (dlg.DialogResult == DialogResult.OK)
        {
            listBoxLibraryBooks.Items.Add(dlg.Book);
        }
        dlg.Dispose();
    }

Why is this happening?

Answer 1

It looks like you never put a LibraryBook instance into the Book property.