Implement Multiselect in WPF DataGrid in proper WPF way with Multiselect Behavior and without any code behind
Introduction
In this article you will see how to implement multiselect in WPF DataGrid in proper way when you are following MVVM pattern. In this article you will see how to implement a behavior to your DataGrid so that we can achieve multiselect.
Behaviors are introduced with Expression Blend, to encapsulate pieces of functionality into a reusable component. These components can then be attached to controls to give them an additional behavior.
Background
Multiselect is something which is like a must have feature in any control which displays multiple items, but unfortunately it is not straight forward in WPF when you are an MVVM developer. We need to attach a multiselect behavior to controls like DataGrid in order to get multiselect working.
Problem it addresses
In DataGrid, the property “SelectedItems” does not have an accessible setter. So we need alternate ways to get the list of selected items.
Requirements
Here you need to add reference to System.Windows.Interactivity. If you have installed blend, then it is available in C:\Program Files (x86)\Microsoft SDKs\Expression\Blend 3\Interactivity\Libraries\WPF.
Using the code
- Add reference to System.Windows.Interactivity
- Add DataGrid to your xaml.
<window […]="" xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity">
<grid>
<datagrid itemssource="{Binding Values}">
</datagrid>
</grid>
</window>- create view model with a public property called SelectedItems.
namespace WpfApplicationTest
{
using System.Collections;
using System.Collections.Specialized;
internal class MainWindowViewModel
{
public IList Values { get; set; }
public MainWindowViewModel()
{
this.Values = new StringCollection { "test1", "test2", "test3", "test4", "test5" };
}
public IList SelectedItems { get; set; }
}
}- Create multiselect behavior as shown below.
namespace WpfApplicationTest
{
using System;
using System.Windows.Controls;
using System.Windows.Interactivity;
public class MultiSelectBehavior : Behavior<datagrid>
{
protected override void OnAttached()
{
base.OnAttached();
((MainWindowViewModel)this.AssociatedObject.DataContext).SelectedItems = this.AssociatedObject.SelectedItems;
}
}
}- Now add this behavior to DataGrid. Also don’t forget to make SelectionMode=”Extended”. This will help you to select row by pressing Ctrl key.
<window […]="">
<grid>
<datagrid itemssource="{Binding Values}" SelectionMode="Extended">
<i:interaction.behaviors>
<wpfapplicationtest:multiselectbehavior></wpfapplicationtest:multiselectbehavior>
</i:interaction.behaviors>
</datagrid>
</grid>
</window>Point of interest
If you have multiple DataGrid, then you need multiple Multiselect behaviors, one way to avoid this is by creating switch in MultiselectBehavior.
namespace WpfApplicationTest
{
using System;
using System.Windows.Controls;
using System.Windows.Interactivity;
public class MultiSelectBehavior : Behavior<datagrid>
{
protected override void OnAttached()
{
base.OnAttached();
switch (this.AssociatedObject.Name)
{
case "DataGrid1":
((MainWindowViewModel)this.AssociatedObject.DataContext).SelectedItemsForDataGrid1 = this.AssociatedObject.SelectedItems;
break;
case "DataGrid2":
((MainWindowViewModel)this.AssociatedObject.DataContext).SelectedItemsForDataGrid1 = this.AssociatedObject.SelectedItems;
break;
default:
break;
}
}
}
}
I am a lead engineer at a prominent wind turbine manufacturing firm. My interests span a diverse range, and immersing myself in technology is one of them. This platform serves as my primary knowledge base, where I seek information and insights. Moreover, I utilize this platform to share my experiences and experiments, hoping they may benefit those following a similar path. It's important to note that the suggestions I express here are based on my best knowledge at the time of writing and may not necessarily represent the optimal solutions. I wholeheartedly welcome any comments you may have to improve or refine my ideas. Your feedback is greatly appreciated and valued.