How to Track the Current Column Name and Sort Direction In WPF MVVM DataGrid - wpfdatagrid

Question

I need to track the Current Column Name and Sort Direction In WPF MVVM DataGrid. I know how to do it in code behind. Plase see the code as follows:
private void columnHeader_Click(object sender, RoutedEventArgs e)
{
var columnHeader = sender as DataGridColumnHeader;
if (columnHeader != null)
{
columnName = ((DataGridColumnHeader)sender).Content.ToString();
ListSortDirection sortDirection = (((DataGridColumnHeader)sender).SortDirection != ListSortDirection.Ascending) ?
ListSortDirection.Ascending : ListSortDirection.Descending;
txb1.Text = columnName;
txb2.Text = sortDirection.ToString();
}
}
However, I am blocked in MVVM. In the View Model, I wrote codes in method sort() in SortCommand, but they did not work. I would appreciate if any one can help. Below are three files.
1) Xaml
<Window x:Class="SortSampleMVVM1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:se="clr-namespace:Microsoft.Expression.Interactivity.Core;assembly=Microsoft.Expression.Interactions"
Title="MainWindow" Height="350" Width="525">
<Grid>
<DataGrid x:Name="Test"
ItemsSource="{Binding}"
AutoGenerateColumns="False" >
<DataGrid.ColumnHeaderStyle>
<Style TargetType="{x:Type DataGridColumnHeader}">
<Setter Property="Command"
Value="{Binding SortCommand}"/>
<Setter Property="CommandParameter"
Value="{Binding Path=Content, RelativeSource={RelativeSource Self}}"/>
<Style.Triggers>
<Trigger Property="IsPressed" Value="True">
<Setter Property="Background" Value="Red" />
</Trigger>
</Style.Triggers>
</Style>
</DataGrid.ColumnHeaderStyle>
<DataGrid Name="dataGrid1" AutoGenerateColumns="False" ItemsSource="{Binding ViewSource.View}" >
<DataGrid.Columns>
<DataGridTextColumn Header="ID" Binding="{Binding ID }"
SortDirection="Descending" />
<DataGridTextColumn Header="firstName" Binding="{Binding firstName}"/>
<DataGridTextColumn Header="lastName" Binding="{Binding lastName}"/>
</DataGrid.Columns>
</DataGrid>
<Label Content="Column Name" HorizontalAlignment="Left" Margin="100,166,0,0" VerticalAlignment="Top"/>
<TextBox HorizontalAlignment="Left" Height="23" Margin="250,169,0,0" TextWrapping="Wrap" Name="txb1" Text="{Binding ColumnName}" VerticalAlignment="Top" Width="150" />
<Label Content="Sorting direction" HorizontalAlignment="Left" Margin="100,229,0,0" VerticalAlignment="Top"/>
<TextBox HorizontalAlignment="Left" Height="23" Margin="250,232,0,0" TextWrapping="Wrap" Name="txb2" Text="{Binding SortDirection}" VerticalAlignment="Top" Width="150" />
<Button Content="Refresh" Name="btnRefresh1" HorizontalAlignment="Left" Margin="140,273,0,0" VerticalAlignment="Top" Width="75" Command="{Binding Refresh1Command}" />
<Button Content="Refresh Keep Sort" Name="btnRefresh2" HorizontalAlignment="Left" Margin="282,273,0,0" VerticalAlignment="Top" Width="125" Command="{Binding Refresh2Command}" />
</Grid>
</Window>
2) Code behind
using System.Windows;**strong text**
using System.Collections.ObjectModel;
using System.Collections.Generic;
namespace SortSampleMVVM1
{
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new SortViewModel();
}
}
}
3) View Model
using System;
using System.ComponentModel;
using System.Windows.Input;
using System.Windows.Controls.Primitives;
using System.Windows;
using System.Windows.Data;
using System.Collections.ObjectModel;
namespace SortSampleMVVM1
{
class SortViewModel: INotifyPropertyChanged
{
public CollectionViewSource ViewSource { get; set; }
public ObservableCollection<MyData> Collection {get; set;}
private string _columnName;
private ListSortDirection _sortDirection;
private ICommand _sortCommand;
private ICommand _refresh1Command;
private ICommand _refresh2Command;
public SortViewModel ()
{
this.Collection = new ObservableCollection<MyData>();
Collection.Add(new MyData(1, "David", "Lee"));
Collection.Add(new MyData(2, "John", "kim"));
Collection.Add(new MyData(3, "Michael", "Wadsworth"));
Collection.Add(new MyData(4, "Chris", "Smith"));
Collection.Add(new MyData(5, "Peter", "Chen"));
Collection.Add(new MyData(6, "Jonas", "Zhang"));
this.ViewSource = new CollectionViewSource();
ViewSource.Source = this.Collection;
}
public event PropertyChangedEventHandler PropertyChanged;
public string ColumnName
{
get { return _columnName; }
set
{
_columnName = value;
OnPropertyChanged("ColumnName");
}
}
public ListSortDirection SortDirection
{
get { return _sortDirection; }
set
{
_sortDirection = value;
OnPropertyChanged("SortDirection");
}
}
protected void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this,
new PropertyChangedEventArgs(propertyName));
}
}
#region SortCommand
public ICommand SortCommand
{
get
{
if (_sortCommand == null)
{
_sortCommand = new RelayCommand(param => this.sort(),
null);
}
return _sortCommand;
}
}
private void sort()
{
//var columnHeader = (object)sender as DataGridColumnHeader;
//if (columnHeader != null)
//{
// _columnName = ViewSource.GetValuecolumnName ((DataGridColumnHeader)sender).Content.ToString();
// ListSortDirection sortDirection = (((DataGridColumnHeader)sender).SortDirection != ListSortDirection.Ascending) ?
// ListSortDirection.Ascending : ListSortDirection.Descending;
//}
}
#endregion
#region Refresh1Command
public ICommand Refresh1Command
{
get
{
if (_refresh1Command == null)
{
_refresh1Command = new RelayCommand(param => this.Refresh1(),
null);
}
return _refresh1Command;
}
}
private void Refresh1()
{
ViewSource.SortDescriptions.Clear();
_columnName = "firstName";
_sortDirection = ListSortDirection.Descending;
ViewSource.SortDescriptions.Add(new SortDescription(_columnName, _sortDirection));
ViewSource.View.Refresh();
}
#endregion
#region Refresh2Command
public ICommand Refresh2Command
{
get
{
if (_refresh2Command == null)
{
_refresh2Command = new RelayCommand(param => this.Refresh2(),
null);
}
return _refresh2Command;
}
}
private void Refresh2()
{
ViewSource.SortDescriptions.Clear();
ViewSource.SortDescriptions.Add(new SortDescription(_columnName, _sortDirection));
ViewSource.View.Refresh();
}
#endregion
}
}

Answer 1

You can use following styling to get the column header.
<Style TargetType="{x:Type DataGridColumnHeader}">
<Setter Property="Command"
Value="{Binding DataContext.MyCommand}"/>
<Setter Property="CommandParameter"
Value="{Binding Path=Content, RelativeSource={RelativeSource Self}}"/>
<Style.Triggers>
<Trigger Property="IsPressed" Value="True">
</Trigger>
</Style.Triggers>
</Style>
</DataGrid.ColumnHeaderStyle>
You have to create the Command 'MyCommand' in your view model. then as the parameter of your execute method you will get column header name.