附加信息：未將對象引用設置爲對象的實例

Question

所以即時獲取此錯誤，我不明白爲什麼即時獲取它。我試圖尋找答案，但每個問題都是如此獨特，以至於他們不適用於我的問題。

這是我到目前爲止。

class customer{ 
    public string sFirstName { get; set; } 
    public string sLastName { get; set; } 
    public int iAge { get; set; } 
} 
class customerObject{ 
    public static List<customer> lstStaticUsers { get; set; } 
    public customerObject(){ 
     lstStaticcustomer = new List<customer>(); 
    } 
    public static void AddNewStaticUser(string FirstName, string LastName, int Age) 
    { 
     lstStaticcustomer.Add(new customer{sFirstName = FirstName, sLastName = LastName, iAge = Age}); 
    } 
} 

這裏是我的窗口

public partial class wndCustomerInfo : Window 
{ 
    public wndCustomerInfo() 
    { 
     InitializeComponent(); 
    } 

    private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e) 
    { 
     this.Hide(); 
     e.Cancel = true; 
    } 

    private void btnSubmitForm_Click(object sender, RoutedEventArgs e) 
    { 
     customerObject.AddNewStaticcustomer(txtFirstName.Text, txtLastName.Text, Convert.ToInt32(txtAge.Text)); 
     lblMessage.Content = "Created new user: " + txtFirstName.Text; 
    } 
} 

那麼這裏就是打開上述

public partial class MainWindow : Window 
{ 

    wndCustomerInfo wndCustomerInfoForm; 

    public MainWindow() 
    { 
     InitializeComponent(); 
     Application.Current.ShutdownMode = ShutdownMode.OnMainWindowClose; 
     wndCustomerInfoForm= new wndCustomerInfo(); 
    } 

    private void btnSave_Click(object sender, RoutedEventArgs e) 
    { 
     this.Hide(); 
     wndCustomerInfoForm.ShowDialog(); 
     this.Show(); 
    } 
} 

的一個。如果有人可以幫助這將是偉大的我的主窗口。 IM樣的新的C＃，所以請好的

Answer 1

製作customObject的構造static：

static customerObject(){ 
    lstStaticcustomer = new List<customer>(); 
}