[英]Populating a combobox with c# using MVVM paradigm
我想在組合框中顯示“用戶組”,然后將選定的用戶組鍵綁定到我的視圖模型中的變量。 我正在使用MVVM范例,我知道它非常接近工作,但是我看不出問題出在哪里。 通過網絡調用登錄后,動態填充用戶組。 我知道綁定正在工作,因為如果我在xaml中刪除DisplayMemberPath屬性,則會看到這些組。
我班的UserGroup
public class UserGroup
{
public long ugp_id;
public String groupName;
public float ugp_credits;
public String logo;
public UserGroup()
{
}
}
我有一個XAML
....
<ComboBox Grid.Row="0" Grid.Column="2" Height="30" VerticalAlignment="Top" Margin="0,4,0,0"
ItemsSource="{Binding userGroupCollection, Mode=OneWay}"
DisplayMemberPath="groupName"
SelectedValue="{Binding SelectedUgpId}"
SelectedValuePath="ugp_id" >
在我的ViewModel類中,我建立了一個可觀察的集合:
public ObservableCollection<UserGroup> _userGroupCollection;
public ObservableCollection<UserGroup> userGroupCollection
{
get
{
return _userGroupCollection;
}
set
{
if (_userGroupCollection != value)
{
this._userGroupCollection = value;
DynamicOnPropertyChanged();
}
}
}
在網絡通話之后,這些數據看起來就像我期望的那樣...
但是當我查看頁面時查看輸出窗口時,我看到組合框條目為空白(但顯示了正確的數字),並且此錯誤:
'i3SoftClient.vshost.exe' (CLR v4.0.30319: i3SoftClient.vshost.exe): Loaded 'C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\PresentationFramework-SystemCore\v4.0_4.0.0.0__b77a5c561934e089\PresentationFramework-SystemCore.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
System.Windows.Data Error: 40 : BindingExpression path error: 'ugp_id' property not found on 'object' ''UserGroup' (HashCode=29245900)'. BindingExpression:Path=ugp_id; DataItem='UserGroup' (HashCode=29245900); target element is 'ComboBox' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Error: 40 : BindingExpression path error: 'groupName' property not found on 'object' ''UserGroup' (HashCode=29245900)'. BindingExpression:Path=groupName; DataItem='UserGroup' (HashCode=29245900); target element is 'ComboBox' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Error: 40 : BindingExpression path error: 'ugp_id' property not found on 'object' ''UserGroup' (HashCode=29245900)'. BindingExpression:Path=ugp_id; DataItem='UserGroup' (HashCode=29245900); target element is 'ComboBox' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Error: 40 : BindingExpression path error: 'ugp_id' property not found on 'object' ''UserGroup' (HashCode=29245900)'. BindingExpression:Path=ugp_id; DataItem='UserGroup' (HashCode=29245900); target element is 'ComboBox' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Error: 40 : BindingExpression path error: 'ugp_id' property not found on 'object' ''UserGroup' (HashCode=6695955)'. BindingExpression:Path=ugp_id; DataItem='UserGroup' (HashCode=6695955); target element is 'ComboBox' (Name=''); target property is 'NoTarget' (type 'Object')
我環顧了四周,但似乎無法理解該錯誤消息。
您必須這樣做:
public long ugp_id { get; set; }
public String groupName { get; set; }
現在再試一次:)
錯誤的是那些無效的屬性,它們僅僅是變量:)對於要在任何成員上進行綁定的綁定,您都應該如上所述聲明 :)
您不能使用公共字段進行綁定。 您必須使用屬性
public class UserGroup
{
public long ugp_id { get; set; };
public String groupName { get; set; };
public float ugp_credits { get; set; };
public String logo { get; set; };
public UserGroup()
{
}
}
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