不包含发票定义？

Question

I'm trying to data transfer from form 1 to form 2 But it throw error even i have add the Invoice.cs class in my project.

Throw error:

'System.Windows.Forms.Form' does not contain a definition for 'Invoice' and no extension method 'Invoice' accepting a first argument of type 'System.Windows.Forms.Form' could be found (are you missing a using directive or an assembly reference?)

Form 1

private void button5_Click(object sender, EventArgs e)
    {
        Form InvoiceSystem = new Form();
        if (InvoiceSystem == null)
        {
            Invoice invoice = new Invoice();
            invoice.id = Convert.ToInt16(textId.Text);
            invoice.nameItem = textNameiTem.Text;
            invoice.priceItem = Convert.ToDouble(textPrice.Text);
            invoice.qty = Convert.ToInt16(textQty.Text);
            invoice.amount = Convert.ToDouble(textAmount.Text);
            invoice.date = Convert.ToInt16(textDate.Text);
            invoice.invoiceNo = Convert.ToInt16(textInvoice.Text);
            InvoiceSystem.Invoice = invoice;
            InvoiceSystem.Show();
        }
    }

Form 2

  public partial class InvoiceSystem : Form
        {
            public Invoice Invoice
            {
              set
        {
            textId.Text = value.id.ToString();
            textitem.Text = value.nameItem;
            textPrice.Text = value.priceItem.ToString();
            textQty.Text = value.qty.ToString();
            textAmt.Text = value.amount.ToString();
            textdate.Text = value.date.ToString();
            textInvoiceNo.Text = value.invoiceNo.ToString();
        }
    }

In Invoice.cs class

public class Invoice
{
    public int id {get;set;}
    public string nameItem { get; set; }
    public double priceItem{get;set;}
    public int qty { get; set; }
    public double amount { get; set; }
    public int date { get; set; }
    public int invoiceNo { get; set; }
}

Answer 1

You've declared your variable as a Form :

Form InvoiceSystem = new Form();

Form itself doesn't have any of your customizations. It's the base class for all forms, built into the framework. Your custom class is InvoiceSystem , which you've made as a specific kind of form. Use that:

InvoiceSystem invoiceSystem = new InvoiceSystem();

(Note also that I made the variable name lowercase. So you'll need to update the other lines of code which reference that variable as well. Don't name variables with the same names as your classes. It will lead to confusion.)

---

Also note that your if statement is superfluous:

Form InvoiceSystem = new Form();
if (InvoiceSystem == null)
//...

The immediate preceding line instantiated the variable. So that variable will never be null on that next line.