我試圖編寫簡單的成員資格類。第一個類名是Customer,它具有其他類,如繼承自Customer類的Silver_Customer,Gold_Customer。繼承對象中的空引用問題
我在簡單的Windows應用程序中使用這些類:
public Customer customer;
public Form_MURAT_TURAN()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
Product p1 = new Product("Blouse", 152.80);
Product p2 = new Product("T-Shirt", 50.25);
.....
lbProducts.Items.Add(p1);
lbProducts.Items.Add(p2);
.....
}
private void btnCustomer_Click(object sender, EventArgs e)
{
Customer customer = new Standard_Customer(txtName.Text, txtSurname.Text, 0);
customer.Name = "Mark 1";
customer.TotalAmount = 5;
gbCustomer.Enabled = false;
gbProduct.Enabled = true;
set_info(customer.customerType(), customer.Name + " " + customer.Surname, customer.TotalAmount);
}
private void btnAddToBasket_Click(object sender, EventArgs e)
{
customer.Name = "Mark 2";
}
一切工作正常,除了btnAddToBasket_Click方法。 customer.Name =「Mark 2」;行給我NullReferenceException
錯誤,但是customer.Name =「標記1」行工作。
您能向我們展示Customer,Standard_Customer類的定義嗎? – tomfanning 2011-05-30 19:10:22
請參閱http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net – 2011-05-30 19:10:54