I try to dynamically create and assign a DataTemplate to a HeaderTemplate of DataGrid through code. To do this I have a method GetDatatemplate(string fromstring) that defines an XML literal and then uses this to create a DataTemplate. This works fine as long as I don't include the MouseLeftButtonDown event handler in the DataTemplate.
My DataTemplate saved in string variable called StringHeaderTemplate in code-behind of MainWindow.xaml.cs:
private string StringHeaderTemplate =@"<DataTemplate>
<DataTemplate.Resources>
<ControlTemplate x:Key=""imgNo"" TargetType=""{x:Type Control}"">
<Image Source = ""pack://application:,,,/Images/upArrow.png"" />
</ControlTemplate >
<ControlTemplate x:Key=""imgUp"" TargetType=""{x:Type Control}"">
<Image Source = ""pack://application:,,,/Images/upArrow.png"" />
</ControlTemplate >
<ControlTemplate x:Key=""imgDown"" TargetType=""{x:Type Control}"" >
<Image Source = ""pack://application:,,,/Images/downArrow.png"" />
</ControlTemplate >
</DataTemplate.Resources>
<Grid Background=""Transparent"" MouseLeftButtonDown=""Grid_MouseLeftButtonDown"">
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Button Content=""Hello""/>
<TextBlock Grid.Row=""1"" HorizontalAlignment= ""Center"" Text = ""TextBlock"" />
<CheckBox Grid.Row= ""2"" HorizontalAlignment= ""Center"" IsChecked= ""True"" />
</Grid >
</DataTemplate>";
And the method which gets DataTemplate:
private DataTemplate GetDatatemplate(string fromstring)
{
ParserContext context = new ParserContext();
context.XmlnsDictionary.Add("", "http://schemas.microsoft.com/winfx/2006/xaml/presentation");
context.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml");
return (DataTemplate)XamlReader.Parse(fromstring, context);
}
Then I just apply this DataTemplate to HeaderTemplate of DataGrid:
private void dg_AutoGeneratingColumn_1(object sender, DataGridAutoGeneratingColumnEventArgs e)
{
DataTemplate dtCell = null;
DataTemplate dtHeader = null;
string dtString = string.Empty;
string dtHeaderString = string.Empty;
switch(Type.GetTypeCode(e.PropertyType))
{
case TypeCode.String:
dtString = StringTemplate.Replace("xxColumnxx", e.PropertyName);
dtHeaderString=StringHeaderTemplate;
break;
}
if(!string.IsNullOrEmpty(dtString))
{
dtCell = GetDataTemplateForDataGrid(dtCellString);
dtHeader = GetDataTemplateForDataGrid(dtHeaderString);
DataGridTemplateColumn c = new DataGridTemplateColumn()
{
CellTemplate = dtCell,
HeaderTemplate = dtHeader,
};
e.Column = c;
}
}
The event handler is really simple:
private void Grid_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
MessageBox.Show(DateTime.Now.ToString());
}
The exception I get is a XamlParseException that has an InnerException of type ArgumentException that says:
"Cannot bind to the target method because its signature or security transparency is not compatible with that of the delegate type."
Any ideas what to do?
Update:
I've tried to bind through Command, however the CallSortingCommand is not called. Maybe you know what I am doing wrong?
<Grid Background=""Transparent"">
<i:Interaction.Triggers>
<i:EventTrigger EventName=""MouseLeftButtonDown"">
<prism:InvokeCommandAction Command = ""{Binding
RelativeSource={RelativeSource AncestorType=Window,
Mode=FindAncestor}, Path=DataContext.CallSortingCommand}"" />
</i:EventTrigger>
</i:Interaction.Triggers>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Button Content=""Hello""/>
<TextBlock Grid.Row=""1"" HorizontalAlignment= ""Center"" Text = ""TextBlock"" />
CheckBox Grid.Row= ""2"" HorizontalAlignment= ""Center"" IsChecked= ""True"" />
</Grid >
It is an interesting problem, 'cause possible solution could be in finding object you want to subscribe to in visual tree, after data template is applied. But it is a column and it would be hard to access visual tree in that case.
I'd suggest to go with Interactions, that allow to define event triggers in XAML. Please have a look at the code below:
private string StringHeaderTemplate = @"<DataTemplate>
<Grid Background=""Transparent"">
<i:Interaction.Triggers>
<i:EventTrigger EventName=""MouseLeftButtonDown"">
<si:CallMethodAction MethodName = ""Grid_MouseLeftButtonDown"" TargetObject=""{Binding RelativeSource={RelativeSource AncestorType=Window}}""/>
</i:EventTrigger>
</i:Interaction.Triggers>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Button Content=""Hello""/>
<TextBlock Grid.Row=""1"" HorizontalAlignment= ""Center"" Text = ""TextBlock"" />
<CheckBox Grid.Row= ""2"" HorizontalAlignment= ""Center"" IsChecked= ""True"" />
</Grid >
</DataTemplate>";
public void Grid_MouseLeftButtonDown(object sender, RoutedEventArgs e)
{
MessageBox.Show(DateTime.Now.ToString());
}
private DataTemplate GetDatatemplate(string fromstring)
{
ParserContext context = new ParserContext();
context.XmlnsDictionary.Add("", "http://schemas.microsoft.com/winfx/2006/xaml/presentation");
context.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml");
context.XmlnsDictionary.Add("i", "clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity");
context.XmlnsDictionary.Add("si", "clr-namespace:Microsoft.Expression.Interactivity.Core;assembly=Microsoft.Expression.Interactions");
return (DataTemplate)XamlReader.Parse(fromstring, context);
}
P.S. Please pay attention to public access modifier of Grid_MouseLeftButtonDown event handler, with private it will not work.
UPDATE
Full source code:
XAML
<Window x:Class="DataGridDataTemplateInCode.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:DataGridDataTemplateInCode"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Grid>
<DataGrid Name="dg" ItemsSource="{Binding Items}" AutoGeneratingColumn="dg_AutoGeneratingColumn" />
</Grid>
</Window>
C#
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new MainWindowViewModel();
}
private string StringHeaderTemplate = @"<DataTemplate>
<Grid Background=""Transparent"">
<i:Interaction.Triggers>
<i:EventTrigger EventName=""PreviewMouseLeftButtonDown"">
<si:CallMethodAction MethodName = ""Grid_MouseLeftButtonDown"" TargetObject=""{Binding RelativeSource={RelativeSource AncestorType=Window}}""/>
</i:EventTrigger>
</i:Interaction.Triggers>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Button Content=""Hello""/>
<TextBlock Grid.Row=""1"" HorizontalAlignment= ""Center"" Text = ""Grid_MouseLeftButtonDown"" />
<CheckBox Grid.Row= ""2"" HorizontalAlignment= ""Center"" IsChecked= ""True"" />
</Grid >
</DataTemplate>";
private string DateTimeWithCommandHeaderTemplate = @"<DataTemplate>
<Grid Background=""Transparent"">
<i:Interaction.Triggers>
<i:EventTrigger EventName=""MouseLeftButtonDown"">
<i:InvokeCommandAction Command = ""{Binding DataContext.CallSortingCommand, RelativeSource={RelativeSource AncestorType=Window}}""/>
</i:EventTrigger>
</i:Interaction.Triggers>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Button Content=""Hello""/>
<TextBlock Grid.Row=""1"" HorizontalAlignment= ""Center"" Text = ""CallSortingCommand"" />
<CheckBox Grid.Row= ""2"" HorizontalAlignment= ""Center"" IsChecked= ""True"" />
</Grid >
</DataTemplate>";
private string TimeCellTemplate = @"<DataTemplate>
<TextBlock HorizontalAlignment= ""Center"" Text = ""{Binding Time}"" />
</DataTemplate>";
private string DescCellTemplate = @"<DataTemplate>
<TextBlock HorizontalAlignment= ""Center"" Text = ""{Binding Desc}"" />
</DataTemplate>";
public void Grid_MouseLeftButtonDown(object sender, RoutedEventArgs e)
{
//MessageBox.Show(DateTime.Now.ToString());
var vm = DataContext as MainWindowViewModel;
vm.Items[0].Desc += "+";
}
private DataTemplate GetDatatemplate(string fromstring)
{
ParserContext context = new ParserContext();
context.XmlnsDictionary.Add("", "http://schemas.microsoft.com/winfx/2006/xaml/presentation");
context.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml");
context.XmlnsDictionary.Add("i", "clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity");
context.XmlnsDictionary.Add("si", "clr-namespace:Microsoft.Expression.Interactivity.Core;assembly=Microsoft.Expression.Interactions");
return (DataTemplate)XamlReader.Parse(fromstring, context);
}
private void dg_AutoGeneratingColumn(object sender, DataGridAutoGeneratingColumnEventArgs e)
{
DataTemplate dtHeader = null;
string dtString = string.Empty;
string dtHeaderString = string.Empty;
DataGridTemplateColumn column = null;
switch (Type.GetTypeCode(e.PropertyType))
{
case TypeCode.String:
{
column = new DataGridTemplateColumn()
{
CellTemplate = GetDatatemplate(DescCellTemplate),
HeaderTemplate = GetDatatemplate(StringHeaderTemplate),
};
}
break;
case TypeCode.DateTime:
{
column = new DataGridTemplateColumn()
{
CellTemplate = GetDatatemplate(TimeCellTemplate),
HeaderTemplate = GetDatatemplate(DateTimeWithCommandHeaderTemplate),
};
}
break;
}
if (column != null)
{
e.Column = column;
}
}
}
public class MainWindowViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public MainWindowViewModel()
{
for (int i = 0; i < 10; i++)
{
_collection.Add(new MyObject() { Time = DateTime.Now.AddSeconds(i), Desc = i.ToString() });
}
CallSortingCommand = new DelegateCommand(OnCallSortingCommand, (o) => true);
}
private void OnCallSortingCommand(object obj)
{
MessageBox.Show("From OnCallSortingCommand");
}
public ICommand CallSortingCommand { get; set; }
private ObservableCollection<MyObject> _collection = new ObservableCollection<MyObject>();
public ObservableCollection<MyObject> Items
{
get
{
return _collection;
}
}
protected void OnPropertyChanged([CallerMemberName] string property = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));
}
}
public class MyObject : INotifyPropertyChanged
{
public DateTime Time { get; set; }
private string _desc;
public string Desc
{
get { return _desc; }
set { _desc = value; PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Desc))); }
}
public event PropertyChangedEventHandler PropertyChanged;
}
public class DelegateCommand : ICommand
{
private readonly Action<object> _execute;
private readonly Func<object, bool> _canExecute;
public event EventHandler CanExecuteChanged;
public DelegateCommand(Action<object> execute, Func<object, bool> canExecute)
{
_execute = execute;
_canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
return _canExecute(parameter);
}
public void Execute(object parameter)
{
_execute(parameter);
}
}