[我们在SelectedItem
中看到围绕DataGrid
属性的某些奇怪行为。 一些背景信息:
DataGrid
显示对我们数据库的查询结果。有一个按钮,允许用户手动刷新DataGrid
中的结果。有一种自动刷新机制,结果将每30秒自动刷新一次。
我们看到的是,SelectedItem
属性将在自动刷新发生时始终成为Datagrid的ItemsSource的索引0。但是我们希望当前选定的行在刷新后保持选定的行。但是,如果用户手动单击刷新,则刷新后所选行将保持不变,这很奇怪,因为刷新逻辑正在运行相同的代码。是的,我们的代码可以记住当前选定的项目,刷新完成后,该项目将再次设置。
以下是一些相关代码:
<UserControl.Resources>
<CollectionViewSource Source="{Binding DataGridResults}" x:Key="ReferralItemsSource"/>
</UserControl.Resources>
<customControls:CustomDataGrid x:Name="GridControl"
ItemsSource="{Binding Source={StaticResource ReferralItemsSource}}"
SelectedItem="{Binding DataContext.SelectedReferral, RelativeSource={RelativeSource AncestorType={x:Type UserControl}}}"
IsReadOnly="False"
IsSynchronizedWithCurrentItem="True"
SelectionMode="Single">
private async void RefreshWorklist(bool invokedByAutoRefresh = false)
{
try
{
if (Initialising || ShowSpinner || IsProcessing || ShowRefreshSpinner || IsCurrentWorklistDeleted || !_sessionData.IsActive()) return;
IsProcessing = true;
RefreshWorklistCommand.RaiseCanExecuteChanged();
if (CurrentWorklistId != null)
{
var selectedReferralId = SelectedReferral.pk_Referral_ID;
if (invokedByAutoRefresh)
{
// Refresh has been invoked by _timer, so show spinner on the results page only
ShowRefreshSpinner = true;
}
else
{
// User has manually clicked refresh button so show app wide spinner
ShowSpinner = true;
if (_timer != null)
{
SetupWorklistRefreshTimer(); // Setup _timer again so that it will refresh again at an appropriate time
}
}
Referrals = await _referralRepository.GetReferralsFromWorklistAsync(CurrentWorklistId.Value, invokedByAutoRefresh);
if (Filters.Count > 0)
{
var listOfReferralPks = ReferralFiltering.GetFilteredResults(Referrals, Filters.Where(f => f.HasBeenApplied).ToList());
var filteredResults = Referrals.Where(r => listOfReferralPks.Contains(r.pk_Referral_ID)).ToList();
DataGridResults = MapReferralLookupItemsToReferralLookupItemViewModels(filteredResults);
}
else
{
DataGridResults = MapReferralLookupItemsToReferralLookupItemViewModels(Referrals);
}
SelectedReferral = DataGridResults.FirstOrDefault(r => r.pk_Referral_ID == selectedReferralId);
}
}
catch (Exception e)
{
_errorHandler.DisplayError(e);
}
}
如前所述,通过RefreshWorklist()
调用的手动刷新将调用Command
:
private void Execute_RefreshWorklist()
{
RefreshWorklist();
}
或自动通过使用Timer
:
private void SetupWorklistRefreshTimer()
{
_timer?.Dispose();
var refreshInterval = _userSettingsRepository.GetIntegerSystemSetting("ReferralsWorklistRefreshInterval");
if (refreshInterval <= 0) return; // If this is 0 or below then the refresh should be disabled
if (refreshInterval < 10) // If it is less than 10 then set it to 10 to avoid too many MT calls
{
refreshInterval = 10;
}
var timeUntilFirstTick = refreshInterval * 1000;
_timer = new Timer((s) => RefreshWorklist(true), null, timeUntilFirstTick, refreshInterval * 1000);
}
最后是SelectedItem
属性视图模型绑定属性:
public ReferralLookupItemViewModel SelectedReferral
{
get { return _selectedReferral; }
set
{
if (_selectedReferral != value)
{
_selectedReferral = value;
OnPropertyChanged();
}
}
}
有人对为什么会发生这种行为有任何想法吗?与Timer
有关吗?我知道这不是一个简单的问题,因此请询问更多信息。
您需要使用UI UI线程上]在Binding
中分配属性。
用Timer
替换DispatcherTimer
,或在调用Dispatcher.Invoke
时在现有的Dispatcher.BeginInvoke
回调中使用Timer
或RefreshWorklist
。
通过按Button
,您已经在UI线程上,但是Timer
有其自己的线程,该线程不同于UI线程。在UI线程上调用DispatcherTimer
回调,而不是https://docs.microsoft.com/en-us/dotnet/api/system.windows.threading.dispatchertimer?view=netframework-4.0