我在一个绑定到viewmodel的视图上有一个datagrid。当我初始化视图时，数据网格将填充来自viewmodel（ObservableCollection）的数据。但是，当我尝试对数据进行搜索时，数据网格不会从viewmodel刷新。当我断开我的viewmodel中的代码时，我可以看到ObservableCollection中的结果已经根据我的搜索发生了变化，但不知怎的，它没有被传递回视图。这是我的视图和视图模型（BTW，我正在使用VS2010 RTM）：
namespace Attendance.ViewModels
{
public class EmployeeSelectViewModel : ViewModel, INotifyPropertyChanged
{
#region Entity list and constructor
public EmployeeSelectViewModel()
{
{
Initialize();
}
}
private void Initialize()
{
if (employeeRpository == null)
employeeRpository = new EmployeeRepository();
ListOfEmployees = new ObservableCollection<EmployeeDto>(employeeRpository.GetEmployees(true));
}
private EmployeeRepository employeeRpository;
private ObservableCollection<EmployeeDto> listOfEmployees;
public ObservableCollection<EmployeeDto> ListOfEmployees
{
get { return listOfEmployees; }
set
{
if (listOfEmployees != value)
{
listOfEmployees = value;
NotifyPropertyChanged("ListOfEmployee");
}
}
}
private EmployeeDto selectedEmployee;
public EmployeeDto SelectedEmployee
{
get { return selectedEmployee; }
set
{
if (selectedEmployee != value)
{
selectedEmployee = value;
NotifyPropertyChanged("SelectedEmployee");
}
}
}
#endregion
#region UI control references
/// <summary>
/// search text property
/// </summary>
private string searchText;
public string SearchText
{
get { return searchText; }
set
{
if (searchText != value)
{
searchText = value;
NotifyPropertyChanged("SearchText");
}
}
}
public string Location { get; set; }
#endregion
#region Relay Commands
/// <summary>
/// new command
/// </summary>
private ViewCommand newCommand;
public ViewCommand NewCommand
{
get
{
if (newCommand == null)
newCommand = new ViewCommand(param => this.NewEmployee());
return newCommand;
}
}
private void NewEmployee()
{
NavigationActions.NewEmployeeView();
}
/// <summary>
/// edit command
/// </summary>
private ViewCommand editCommand;
public ViewCommand EditCommand
{
get
{
if (editCommand == null)
{
editCommand = new ViewCommand(param => this.EditEmployee());
}
return editCommand;
}
}
private void EditEmployee()
{
NavigationActions.OpenEmployeeView(SelectedEmployee);
}
/// <summary>
/// save command
/// </summary>
private ViewCommand saveCommand;
public ViewCommand SaveCommand
{
get
{
if (saveCommand == null)
{
saveCommand = new ViewCommand(
param => this.SaveEmployee(),
param => this.CanSaveEmployee
);
}
return saveCommand;
}
}
public void SaveEmployee()
{
employeeRpository.SaveChanges();
}
private bool CanSaveEmployee
{
get { return true; }
}
/// <summary>
/// clear search command
/// </summary>
private ViewCommand clearSearchCommand;
public ViewCommand ClearSearchCommand
{
get
{
if (clearSearchCommand == null)
clearSearchCommand = new ViewCommand(param => this.ClearSearch());
return clearSearchCommand;
}
}
private void ClearSearch()
{
this.SearchText = string.Empty;
ListOfEmployees = new ObservableCollection<EmployeeDto>(employeeRpository.GetEmployees(true));
}
/// <summary>
/// search command
/// </summary>
private ViewCommand searchCommand;
public ViewCommand SearchCommand
{
get
{
if (searchCommand == null)
searchCommand = new ViewCommand(param => this.SearchEmployee());
return searchCommand;
}
}
private void SearchEmployee()
{
if (this.SearchText == string.Empty || this.SearchText == null)
{
NavigationActions.ShowError("Search Employees.", "Please enter your search text ...");
return;
}
ListOfEmployees = new ObservableCollection<EmployeeDto>(employeeRpository.GetEmployeesByQuery(SearchText, Location));
}
/// <summary>
/// exit command
/// </summary>
private ViewCommand exitCommand;
public ViewCommand ExitCommand
{
get
{
if (exitCommand == null)
{
exitCommand = new ViewCommand(param => this.ExitWindow());
}
return exitCommand;
}
}
private void ExitWindow()
{
NavigationActions.CloseCurrentView();
}
#endregion
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(String info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
#endregion
}
}
<Window x:Class="Attendance.Views.EmployeeSelectView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vm="clr-namespace:Attendance.ViewModels"
Title="Employee Maintenance" FocusManager.FocusedElement="{Binding ElementName=txtSearchCriteria}"
Height="525" Width="800" WindowStartupLocation="CenterScreen" WindowState="Normal"
WindowStyle="SingleBorderWindow" Icon="Images/gb_icon.png">
<Window.DataContext>
<vm:EmployeeSelectViewModel />
</Window.DataContext>
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Themes/DataGrid.Generic.xaml" />
</ResourceDictionary.MergedDictionaries>
<!--xml data start-->
<XmlDataProvider x:Key="LocationData" XPath="LocationList/LocationItem" Source="XMLData/Location.xml"/>
<!--xml data end-->
</ResourceDictionary>
</Window.Resources>
<Grid Width="775">
<DockPanel HorizontalAlignment="Left" Width="770">
<!-- TOOLBAR -->
<DockPanel DockPanel.Dock="Top" MinHeight="30" Margin="5">
<ToolBar FontWeight="Bold">
<!-- NEW -->
<Button Name="btnNew" Command="{Binding Path=NewCommand}">
<Button.ToolTip>
<StackPanel>
<Label FontWeight="Bold" Background="SteelBlue" Foreground="White">
Create a new Customer
</Label>
<TextBlock Padding="10" TextWrapping="WrapWithOverflow" Width="200">
Create a new customer in a new Window tab.
</TextBlock>
<Line Stroke="SteelBlue" StrokeThickness="1" X2="200" />
<StackPanel Orientation="Horizontal">
<Image Margin="2" Source="Images/new.png"/>
<Label>Press F1 for more help</Label>
</StackPanel>
</StackPanel>
</Button.ToolTip>
<StackPanel Orientation="Horizontal">
<Image Source="Images/new.png" Width="22" Height="22" Margin="2"/>
<Label VerticalAlignment="Center">_New</Label>
</StackPanel>
</Button>
<!-- EDIT -->
<Button Name="btnEdit" Command="{Binding Path=EditCommand}">
<Button.ToolTip>
<StackPanel>
<Label FontWeight="Bold" Background="SteelBlue" Foreground="White">
Edit the current record
</Label>
<TextBlock Padding="10" TextWrapping="WrapWithOverflow" Width="200">
Edit the current selected Customer.
</TextBlock>
<Line Stroke="SteelBlue" StrokeThickness="1" X2="200" />
<StackPanel Orientation="Horizontal">
<Image Margin="2" Source="Images/dialog-information.png"/>
<Label>Press F1 for more help</Label>
</StackPanel>
</StackPanel>
</Button.ToolTip>
<StackPanel Orientation="Horizontal">
<Image Source="Images/edit.png" Width="22" Height="22" Margin="2" />
<Label VerticalAlignment="Center">_Edit</Label>
</StackPanel>
</Button>
<!-- SEARCH -->
<Separator />
<TextBox Name="txtSearchCriteria"
MinWidth="300" Margin="5"
BorderThickness="1" BorderBrush="LightGray"
FontWeight="Normal" Foreground="Gray" Text="{Binding Path=SearchText}">
</TextBox>
<Button Name="btnSearch" Command="{Binding Path=SearchCommand}">
<Button.ToolTip>
<StackPanel>
<Label FontWeight="Bold" Background="SteelBlue" Foreground="White">
Search
</Label>
<TextBlock Padding="10" TextWrapping="WrapWithOverflow" Width="200">
Search a specific Customer.
</TextBlock>
<Line Stroke="SteelBlue" StrokeThickness="1" X2="200" />
<StackPanel Orientation="Horizontal">
<Image Margin="2" Source="Images/find.png"/>
<Label>Press F1 for more help</Label>
</StackPanel>
</StackPanel>
</Button.ToolTip>
<StackPanel Orientation="Horizontal">
<Image Source="Images/find.png" Width="22" Height="22" Margin="2" />
<Label VerticalAlignment="Center">_Find</Label>
</StackPanel>
</Button>
<Button Name="btnClearSearch" Command="{Binding Path=ClearSearchCommand}">
<Button.ToolTip>
<StackPanel>
<Label FontWeight="Bold" Background="SteelBlue" Foreground="White">
Search
</Label>
<TextBlock Padding="10" TextWrapping="WrapWithOverflow" Width="200">
Clear search results.
</TextBlock>
<Line Stroke="SteelBlue" StrokeThickness="1" X2="200" />
<StackPanel Orientation="Horizontal">
<Image Margin="2" Source="Images/find.png"/>
<Label>Press F1 for more help</Label>
</StackPanel>
</StackPanel>
</Button.ToolTip>
<StackPanel Orientation="Horizontal">
<Label VerticalAlignment="Center">_Clear Search</Label>
</StackPanel>
</Button>
<!-- EXIT -->
<Separator />
<Button Name="btnExit" Command="{Binding Path=ExitCommand}">
<Button.ToolTip>
<StackPanel>
<Label FontWeight="Bold" Background="SteelBlue" Foreground="White">
Start the application
</Label>
<TextBlock Padding="10" TextWrapping="WrapWithOverflow" Width="200">
Start the main application with the M-V-MV pattern.
</TextBlock>
<Line Stroke="SteelBlue" StrokeThickness="1" X2="200" />
<StackPanel Orientation="Horizontal">
<Image Margin="2" Source="Images/dialog-information.png"/>
<Label>Press F1 for more help</Label>
</StackPanel>
</StackPanel>
</Button.ToolTip>
<StackPanel Orientation="Horizontal">
<Image Source="Images/exit.png" Width="22" Height="22" Margin="2" />
<Label VerticalAlignment="Center">_Exit</Label>
</StackPanel>
</Button>
</ToolBar>
</DockPanel>
<!-- LIST -->
<DockPanel DockPanel.Dock="Top" MinHeight="30" Margin="0,0,0,5">
<Label>Location:</Label>
<ComboBox Name="cboLocation" Grid.Column="1" Grid.Row="4"
ItemsSource="{Binding Source={StaticResource LocationData}}"
DisplayMemberPath="location_text" SelectedValuePath="location_value"
SelectedValue="{Binding Path=Location}"
HorizontalAlignment="Left" Width="175" Margin="4" />
</DockPanel>
<DockPanel Margin="5">
<DataGrid ItemsSource="{Binding Path=ListOfEmployees}" AutoGenerateColumns="False" IsReadOnly="True"
Name="dgEmployee" SelectionMode="Single" SelectionUnit="FullRow" CanUserResizeColumns="True"
SelectedItem="{Binding Path=SelectedEmployee}" GridLinesVisibility="Horizontal">
<DataGrid.Columns>
<DataGridTextColumn Header="Employee ID" Width="SizeToCells" MinWidth="125" Binding="{Binding EmployeeID}" />
<DataGridTextColumn Header="First Name" Width="SizeToCells" MinWidth="200" Binding="{Binding FirstName}" />
<DataGridTextColumn Header="Last Name" Width="SizeToCells" MinWidth="200" Binding="{Binding LastName}" />
<DataGridTextColumn Header="Location" Width="SizeToCells" MinWidth="125" Binding="{Binding Location}" />
<DataGridCheckBoxColumn x:Name="Active" Header="Active" Binding="{Binding active}" MinWidth="75" />
</DataGrid.Columns>
</DataGrid>
</DockPanel>
</DockPanel>
</Grid>
答案 0 :(得分：3)
这是我的解决方案：
<DataGrid Name="dgrid" ItemsSource="{Binding UserSettings, IsAsync=True}" AutoGenerateColumns="False">
设置IsAsync = True的关键是允许屏幕绘制
答案 1 :(得分：1)
我的问题已在另一个网站的帖子中得到解答。我没有在我的视图模型中创建ListOfEmployees的新实例，而是清除了现有的实例并添加了我的存储库中的结果：
private void SearchEmployee()
{
if (String.IsNullOrEmpty(this.SearchText) || String.IsNullOrEmpty(this.Location))
{
NavigationActions.ShowError("Search Employees.", "Please enter your search text and select a location...");
return;
}
// clear the list and repopulate based on the search criteria
if (ListOfEmployees != null)
{
ListOfEmployees.Clear();
IList<EmployeeDto> iList = employeeRpository.GetEmployeesByQuery(SearchText, Location, IsActive);
foreach (EmployeeDto value in iList)
ListOfEmployees.Add(value);
}
}
这就是诀窍。
答案 2 :(得分：1)
你之前的代码也应该有用，但是“魔术字符串”阻碍了它。 属性名称是ListOfEmployees，在其setter中，您使用属性名称ListOfEmployee引发PropertyChanged事件。 's'不见了。
小心你的新代码。它将在ListOfEmployees上为每次插入引发CollectionChanged事件，如果您进行多次插入，这可能会使您的应用程序变慢。 对于许多插入，最好从ObservableCollection派生并实现Reset方法，该方法清除基础Items，添加新项并引发Reset类型的CollectionChanged事件。
答案 3 :(得分：1)
我发现了两种刷新DataGrid的方法：
CollectionViewSource.GetDefaultView(collectionName).Refresh();
看起来更自然，因为仅更改受版本影响的单元格。