使用按鈕更改綁定的WPF組合框SelectedItem

Question

我有一個支付期限列表，我已經綁定到一個ComboBox，我想通過點擊按鈕（即一組Previous按鈕）。根據選定的支付期限，我想填充數據庫中的時間記錄列表。

C＃代碼

public TimeSheetViewModel() 
{ 
    BuildPayPeriods(); 
    GetEmployeeList(); 
    GetTimes(SelectedEmployee, SelectedPayPeriod); 
    NextPayPeriod = new RelayCommand(NextPayPeriodCommand); 
    PrevPayPeriod = new RelayCommand(PrevPayPeriodCommand); 
    SelectedPayPeriodChanged = new RelayCommand(SelectPayPeriodCommand); 
} 

public ObservableCollection<PayPeriod> PayPeriods { get; set; } 

private PayPeriod _SelectedPayPeriod; 

public PayPeriod SelectedPayPeriod 
{ 
    get 
    { 
     return _SelectedPayPeriod; 
    } 
    set 
    { 
     _SelectedPayPeriod = value; 
     GetTimes(SelectedEmployee, value); 
     OnPropertyChanged("SelectedPayPeriod") 
    } 
} 

public RelayCommand NextPayPeriod { get; set; } 

void NextPayPeriodCommand(object parameter) 
{ 
    int index = PayPeriods.IndexOf((PayPeriod)parameter); 

    \\EDIT 
    if (index != 0 && CheckForEdits()) 
    { 
     SelectedPayPeriod = PayPeriods[index - 1]; 
    } 
} 

public RelayCommand PrevPayPeriod { get; set; } 

void PrevPayPeriodCommand(Object parameter) 
{ 
    int index = PayPeriods.IndexOf((PayPeriod)parameter); 

    \\EDIT 
    if (index != (PayPeriods.Count - 1) && CheckForEdits()) 
    { 
     SelectedPayPeriod = PayPeriods[index + 1]; 
    } 
} 

public RelayCommand SelectedPayPeriodChanged { get; set; } 

void SelectPayPeriodCommand(Object parameter) 
{ 
    \\EDIT 
    if (parameter != null && CheckForEdits()) 
    { 
     int index = PayPeriods.IndexOf((PayPeriod)parameter); 

     SelectedPayPeriod = PayPeriods[index]; 
    } 
} 

XAML代碼

<Button x:Name="btnPrevWeek" Command="{Binding PrevPayPeriod}" CommandParameter="{Binding Path=SelectedItem, ElementName=comboPayPeriod}"/> 
<ComboBox x:Name="comboPayPeriod" ItemsSource="{Binding PayPeriods}" DisplayMemberPath="Display" SelectedItem="{Binding SelectedPayPeriod, Mode=OneWay}"> 
    <i:Interaction.Triggers> 
     <i:EventTrigger EventName="SelectionChanged"> 
      <i:InvokeCommandAction Command="{Binding SelectedPayPeriodChanged}" CommandParameter="{Binding Path=SelectedItem, ElementName=comboPayPeriod}"/> 
     </i:EventTrigger> 
    </i:Interaction.Triggers> 
</ComboBox> 
<Button x:Name="btnNextWeek" Command="{Binding NextPayPeriod}" CommandParameter="{Binding Path=SelectedItem, ElementName=comboPayPeriod}"> 

我試圖離開了代碼，似乎不相干的格式化和佈局的東西的東西。

SelectedPayPeriodChanged的作品，所以如果我手動更改組合框的選定項目點擊它一切工作正常。另外兩個，PrevPayPeriod和NextPayPeriod，像他們應該觸發，但選定的項目不會改變。

所有的項目都顯示正常，當我點擊不同的支付期時，它會加載一個新的時間表就好了，但單擊prev和next按鈕不會改變我的SelectedPayPeriod。

我對此相當新，所以任何幫助/批評表示讚賞。

感謝

Answer 1

正如評論說明更新您的結合是TwoWay，我還沒有看到你有沒有觸發任何附加價值。結合將採取更新的護理：

<Button x:Name="btnPrevWeek" Command="{Binding PrevPayPeriod}" CommandParameter="{Binding Path=SelectedItem, ElementName=comboPayPeriod}"/> 
<ComboBox x:Name="comboPayPeriod" ItemsSource="{Binding PayPeriods}" DisplayMemberPath="Display" SelectedItem="{Binding SelectedPayPeriod, Mode=TwoWay}" /> 
<Button x:Name="btnNextWeek" Command="{Binding NextPayPeriod}" CommandParameter="{Binding Path=SelectedItem, ElementName=comboPayPeriod}"> 

此外，我認爲你在前面和後面的處理邏輯是相反的，它應該是這樣的：

void PrevPayPeriodCommand(object parameter) 
{ 
    int index = PayPeriods.IndexOf((PayPeriod)parameter); 

    if (index != 0) // set previous if we're not pointing to the first element 
    { 
     SelectedPayPeriod = PayPeriods[index - 1]; 
    } 
} 

void NextPayPeriodCommand(object parameter) 
{ 
    int index = PayPeriods.IndexOf((PayPeriod)parameter); 

    if (index != PayPeriods.Count - 1) // set next if we're not pointing to last element 
    { 
     SelectedPayPeriod = PayPeriods[index + 1]; 
    } 
}