[英]ObservableCollection.CollectionChanged not firing
我有以下界面:
將項目添加到DataGrid
,“ Total column
將根據(價格*數量)進行更新,並且總TextBox
也將包含添加的所有行的總計。
但是,當我更改行的數量時, Total column
更新,但TextBox
不會更新。
這是我的代碼,提前謝謝。
public partial class pgCheckout : Page {
ObservableCollection<SaleItem> items = new ObservableCollection<SaleItem>();
public pgCheckout() {
InitializeComponent();
dgItems.ItemsSource = items;
dgItems.Loaded += SetMinWidths;
items.CollectionChanged += setTotal;
}
public void setTotal(object source, EventArgs e) {
decimal total = 0;
foreach(SaleItem i in items) {
total += i.Total;
}
txtTotal.Text = total.ToString();
}
public void SetMinWidths(object source, EventArgs e) {
foreach (var column in dgItems.Columns) {
if (column.DisplayIndex != 0) {
column.MinWidth = column.ActualWidth;
column.Width = new DataGridLength(1, DataGridLengthUnitType.Star);
}
}
}
private void btnRemove_Click(object sender, RoutedEventArgs e) {
items.RemoveAt(dgItems.SelectedIndex);
}
private void btnAdd_Click(object sender, RoutedEventArgs e) {
bool exist = false;
foreach (SaleItem i in items) {
if (i.ItemID.Equals(txtItemID.Text))
exist = true;
}
if (exist) {
lblErr.Content = "Item already exist";
txtItemID.Text = "";
}
else {
using (var db = new PoSEntities()) {
var query = from i in db.Items
where i.ItemID.Equals(txtItemID.Text.Trim())
select i;
var itm = query.FirstOrDefault();
if (itm == null) {
lblErr.Content = "Invalid Item";
txtItemID.Text = "";
}
else {
txtItemID.Text = "";
lblErr.Content = "";
items.Add(new SaleItem() {
Num = items.Count + 1,
ItemID = itm.ItemID,
Name = itm.Name,
Price = decimal.Round(itm.Price, 2, MidpointRounding.AwayFromZero),
Quantity = 1,
});
}
}
}
}
private void txtItemID_KeyUp(object sender, KeyEventArgs e) {
if (e.Key == System.Windows.Input.Key.Enter) {
btnAdd_Click(txtItemID, e);
}
}
}
class SaleItem : INotifyPropertyChanged {
public int Num { get; set; }
public string ItemID { get; set; }
public string Name { get; set; }
private decimal price;
public decimal Price {
get { return price; }
set {
this.price = value;
OnPropertyChanged("Total");
}
}
public int quantity;
public int Quantity {
get { return quantity; }
set {
this.quantity = value;
OnPropertyChanged("Total");
}
}
public decimal Total {
get { return decimal.Round(Price * Quantity, 2, MidpointRounding.AwayFromZero); }
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName) {
var handler = PropertyChanged;
if (handler != null) {
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
ObservableCollection.CollectionChanged
在集合中添加或刪除某些內容時觸發,而不是正在更新的個別成員。
...
else
{
txtItemID.Text = "";
lblErr.Content = "";
SaleItem newItem = new SaleItem() {
Num = items.Count + 1,
ItemID = itm.ItemID,
Name = itm.Name,
Price = decimal.Round(itm.Price, 2, MidpointRounding.AwayFromZero),
Quantity = 1 };
newItem.PropertyChanged +=
new PropertyChangedEventHandler(newSaleItem_PropertyChanged);
items.Add(newItem);
}
...
這是newSaleItem_PropertyChanged
:
void newSaleItem_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
setTotal(null, null);
}
ObservableCollection<SaleItem> items = new ObservableCollection<SaleItem>();
必須是一個合理的
改為
public ObservableCollection<SaleItem> items {get;set;}
並在構造函數中執行new
或者讓get函數創建一個新對象(如果不存在)
你必須有公共getter / setter才能使用綁定
您的SaleItem
必須實現INotifyPropertyChanged
然后您將擁有PropertyChanged
事件並且您可以訂閱它。 使用INotifyPropertyChanged將有利於綁定。
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