DialogService

• Oct 12, 2023
• 12 minutes to read

The DialogService class allows you to show a modal dialog window from a View Model.

View Example: Use DialogService to Show a Modal Dialog Window

Related services:

• WinUIDialogService - displays a modal window that matches Windows 8/10 style.
• DXMessageBoxService - displays a message box.

Show a Dialog

Follow the steps below to define a simple dialog window and show it from the View Model:

1. Assign a DialogService service to your View in any of the following ways:

   • Use the Quick Actions menu to attach a DialogService to the View.
   • Declare a DialogService in XAML.
   XAML

   <Window ...
           xmlns:dxmvvm="http://schemas.devexpress.com/winfx/2008/xaml/mvvm" 
           xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core">
       <dxmvvm:Interaction.Behaviors>
           <dx:DialogService/>
       </dxmvvm:Interaction.Behaviors>
       <!-- ... -->
   </Window>
   

2. Define dialog content. The following code sample creates a data template and assigns it to the ViewTemplate property:

   XAML

   <dx:DialogService>
       <dx:DialogService.ViewTemplate>
           <DataTemplate>
               <Border>
                   <TextBlock Text="Dialog Content" 
                              HorizontalAlignment="Center" 
                              VerticalAlignment="Center"/>
               </Border>
           </DataTemplate>
       </dx:DialogService.ViewTemplate>
   </dx:DialogService>
   

   You can also use the following techniques to specify dialog content:

   • Create multiple dialog view templates and use the ViewTemplateSelector property to select a template based on a condition.

   • Create a XAML class with dialog content and pass the class name to the ShowDialog method’s documentType parameter.

     Refer to the following help topic for more information on how to pass a View to the ShowDialog method: ViewLocator.

3. Use the DialogStyle and DialogWindowStartupLocation properties to specify the dialog window’s startup location and additional settings:

   XAML

   <dx:DialogService DialogWindowStartupLocation="CenterOwner">
       <dx:DialogService.ViewTemplate>
           <DataTemplate>
               <Border>
                   <TextBlock Text="Dialog Content" 
                              HorizontalAlignment="Center" 
                              VerticalAlignment="Center"/>
               </Border>
           </DataTemplate>
       </dx:DialogService.ViewTemplate>
       <dx:DialogService.DialogStyle>
           <Style TargetType="Window">
               <Setter Property="Height" Value="200"/>
               <Setter Property="Width" Value="300"/>
           </Style>
       </dx:DialogService.DialogStyle>
   </dx:DialogService>
   

4. Access the service from the View Model. The following code sample demonstrates how to access the service from a ViewModelBase descendant View Model:

   C#

   using DevExpress.Mvvm;
   
   namespace DialogServiceExample {
       public class ViewModel : ViewModelBase {
           protected IDialogService DialogService { get { return GetService<IDialogService>(); } }
       }
   }
   

   VB.NET

   Imports DevExpress.Mvvm
   
   Namespace DialogServiceExample
       Public Class ViewModel
           Inherits ViewModelBase
   
           Protected ReadOnly Property DialogService As IDialogService
               Get
                   Return GetService(Of IDialogService)()
               End Get
           End Property
   
       End Class
   End Namespace
   

   Refer to the following help topics for more information on how to access services from different View Model types:

   • Services in ViewModelBase Descendants
   • Services in Generated View Models
   • Services in Custom ViewModels

5. Create a View Model command that calls the DialogService.ShowDialog method to invoke the dialog window:

   C#

   using DevExpress.Mvvm;
   using DevExpress.Mvvm.DataAnnotations;
   
   namespace DialogServiceExample {
       public class ViewModel : ViewModelBase {
           protected IDialogService DialogService { get { return GetService<IDialogService>(); } }
   
           [Command]
           public void ShowDialog() {
               DialogService.ShowDialog(
                   dialogButtons: MessageButton.OKCancel,
                   title: "Dialog Title",
                   viewModel: this
               );
           }
       }
   }
   

   VB.NET

   Imports DevExpress.Mvvm
   Imports DevExpress.Mvvm.DataAnnotations
   
   Namespace DialogServiceExample
       Public Class ViewModel
           Inherits ViewModelBase
   
           Protected ReadOnly Property DialogService As IDialogService
               Get
                   Return GetService(Of IDialogService)()
               End Get
           End Property
   
           <Command>
           Public Sub ShowDialog()
               DialogService.ShowDialog(dialogButtons:=MessageButton.OKCancel, title:="Dialog Title", viewModel:=Me)
           End Sub
       End Class
   End Namespace
   

   Refer to the following help topic for a complete list of the ShowDialog method overloads: DialogServiceExtensions.ShowDialog.

6. Bind the button’s Command property to the created command:

   XAML

   <Window ... >
       <Window.DataContext>
           <local:ViewModel/>
       </Window.DataContext>
       <dxmvvm:Interaction.Behaviors>
           <dx:DialogService>
               <!-- ... -->
           </dx:DialogService>
       </dxmvvm:Interaction.Behaviors>
       <Grid>
           <Button Content="Show Dialog" Command="{Binding ShowDialogCommand}"/>
       </Grid>
   </Window>
   

Bind Dialog Content to Data

Follow the steps in this section to create a dialog with two data-bound editors (First Name and Last Name). The code binds editor values to properties in your View Model:

1. Use the ViewTemplate property to define the dialog layout:

   MainWindow.xaml

   <dx:DialogService.ViewTemplate>
       <DataTemplate>
           <local:DialogView/>
       </DataTemplate>
   </dx:DialogService.ViewTemplate>
   

   DialogView.xaml

   <UserControl ...
                x:Class="DialogServiceExample.DialogView"
                xmlns:dxe="http://schemas.devexpress.com/winfx/2008/xaml/editors">
   
       <Grid.RowDefinitions>
           <RowDefinition />
           <RowDefinition Height="Auto"/>
       </Grid.RowDefinitions>
   
       <StackPanel Orientation="Vertical" VerticalAlignment="Center" HorizontalAlignment="Center">
           <StackPanel Orientation="Horizontal">
               <TextBlock Text="First Name: " VerticalAlignment="Center"/>
               <dxe:TextEdit Text="{Binding FirstName}" Width="100"/>
           </StackPanel>
           <StackPanel Orientation="Horizontal" >
               <TextBlock Text="Last Name: " VerticalAlignment="Center"/>
               <dxe:TextEdit Text="{Binding LastName}" Width="100"/>
           </StackPanel>
       </StackPanel>
   </UserControl>
   

2. Create a dialog View Model:

   DialogViewModel.cs

   public class DialogViewModel : ViewModelBase {
       public string FirstName { get { return GetValue<string>(); } set { SetValue(value); } }
       public string LastName { get { return GetValue<string>(); } set { SetValue(value); } 
   }
   

   DialogViewModel.vb

   Public Class DialogViewModel
       Inherits ViewModelBase
   
       Public Property FirstName As String
           Get
               Return GetValue(Of String)()
           End Get
           Set(ByVal value As String)
               SetValue(value)
           End Set
       End Property
   
       Public Property LastName As String
           Get
               Return GetValue(Of String)()
           End Get
           Set(ByVal value As String)
               SetValue(value)
           End Set
       End Property
   End Class
   

   Editors from the DialogView are bound to the properties above.

3. Create a new instance of the DialogViewModel class and pass this instance to the DialogService.ShowDialog method when a user invokes the dialog:

   MainViewModel.cs

   public class MainViewModel : ViewModelBase {
       public string FirstName { get { return GetValue<string>(); } set { SetValue(value); } }
       public string LastName { get { return GetValue<string>(); } set { SetValue(value); } }
       protected IDialogService DialogService { get { return GetService<IDialogService>(); } }
   
       [Command]
       public void ShowDialog() {
           var dialogViewModel = new DialogViewModel() {
               FirstName = this.FirstName,
               LastName = this.LastName
           };
           MessageResult result;
           result = DialogService.ShowDialog(
               dialogButtons: MessageButton.OKCancel,
               title: "Edit Dialog",
               viewModel: dialogViewModel
           );
           if (result == MessageResult.OK) {
               // ...
           }
       }
   }
   

   MainViewModel.vb

   Public Class MainViewModel
       Inherits ViewModelBase
   
       Public Property FirstName As String
           Get
               Return GetValue(Of String)()
           End Get
           Set(ByVal value As String)
               SetValue(value)
           End Set
       End Property
   
       Public Property LastName As String
           Get
               Return GetValue(Of String)()
           End Get
           Set(ByVal value As String)
               SetValue(value)
           End Set
       End Property
   
       Protected ReadOnly Property DialogService As IDialogService
           Get
               Return GetService(Of IDialogService)()
           End Get
       End Property
   
       <Command>
       Public Sub ShowDialog()
           Dim dialogViewModel = New DialogViewModel() With {
               .FirstName = Me.FirstName,
               .LastName = Me.LastName
           }
           Dim result As MessageResult
           result = DialogService.ShowDialog(dialogButtons:=MessageButton.OKCancel, title:="Edit Dialog", viewModel:=dialogViewModel)
   
           If result = MessageResult.OK Then
               ' ...
           End If
       End Sub
   End Class
   

Define Dialog Buttons

You can use one of the following techniques to define dialog buttons.

Predefined Buttons

Pass a MessageButton enumeration value to the ShowDialog method. In this case, the dialog returns the result of the MessageResult type.

MainViewModel.cs

[Command]
public void ShowDialog() {
    MessageResult result;
    result = DialogService.ShowDialog(
        dialogButtons: MessageButton.OKCancel,
        title: "Edit Dialog",
        viewModel: this
    );
    if (result == MessageResult.OK) {
        // ...
    }
}

MainViewModel.vb

<Command>
Public Sub ShowDialog()
    Dim result As MessageResult
    result = DialogService.ShowDialog(dialogButtons:=MessageButton.OKCancel, title:="Edit Dialog", viewModel:=Me)

    If result = MessageResult.OK Then
        ' ...
    End If
End Sub

UICommand Buttons

Pass a collection of the UICommand objects to the ShowDialog method. In this case, the dialog returns a result of the UICommand type.

MainViewModel.cs

[Command]
public void ShowDialog() {
    // Specify the Apply button:
    var buttonApply = new UICommand() {
        Id = "apply",
        Caption = "Apply",
        Command = new DelegateCommand<CancelEventArgs>(
            cancelArgs => {
                try {
                    // Your "Apply" method 
                }
                catch (Exception e) {
                    // Process errors
                    // ...
                    cancelArgs.Cancel = true;
                }
            },
            // Disable the button if one of the fields is empty:
            cancelArgs => !string.IsNullOrEmpty(dialogViewModel.FirstName) && !string.IsNullOrEmpty(dialogViewModel.LastName)
        ),
        Glyph = new Uri("pack://application:,,,/DevExpress.Images.v23.2;component/SvgImages/Icon Builder/Actions_CheckCircled.svg"),
        IsDefault = true,
        IsCancel = false
    };
    // Specify the Cancel button:
    var buttonCancel = new UICommand() {
        Id = "cancel",
        Caption = "Cancel",
        Command = new DelegateCommand(() => { /* Your "Cancel" method */ }),
        Glyph = new Uri("pack://application:,,,/DevExpress.Images.v23.2;component/SvgImages/Icon Builder/Actions_DeleteCircled.svg"),
        IsDefault = false,
        IsCancel = true
    };

    UICommand result;
    result = DialogService.ShowDialog(
        dialogCommands: new UICommand[] { buttonApply, buttonCancel },
        title: "Edit Dialog",
        viewModel: this
    );

    if (result == buttonApply) {
        // ...
    }
}

MainViewModel.vb

<Command>
Public Sub ShowDialog()
    ' Specify the Apply button:
    Dim buttonApply = New UICommand() With {
        .Id = "apply",
        .Caption = "Apply",
        .Command = New DelegateCommand(Of CancelEventArgs)(Function(cancelArgs)
            Try
                ' Your "Apply" method 
            Catch e As Exception
                ' Process errors
                ' ...
                cancelArgs.Cancel = True
            End Try
        End Function,
        '  Disable the button if one of the fields is empty:
        Function(cancelArgs) Not String.IsNullOrEmpty(dialogViewModel.FirstName) AndAlso Not String.IsNullOrEmpty(dialogViewModel.LastName)),
        .Glyph = New Uri("pack://application:,,,/DevExpress.Images.v23.2;component/SvgImages/Icon Builder/Actions_CheckCircled.svg"),
        .IsDefault = True,
        .IsCancel = False
    }
    '  Specify the Cancel button:
    Dim buttonCancel = New UICommand() With {
        .Id = "cancel",
        .Caption = "Cancel",
        .Command = New DelegateCommand(Function()
            ' Your "Cancel" method
        End Function),
        .Glyph = New Uri("pack://application:,,,/DevExpress.Images.v23.2;component/SvgImages/Icon Builder/Actions_DeleteCircled.svg"),
        .IsDefault = False,
        .IsCancel = True
    }
    Dim result As UICommand
    result = DialogService.ShowDialog(dialogCommands:=New UICommand() {buttonApply, buttonCancel}, title:="Edit Dialog", viewModel:=Me)

    If result = buttonApply Then
        ' ...
    End If
End Sub

Asynchronous Buttons

The DialogService can display asynchronous buttons. These buttons indicate whether the associated asynchronous operation is in progress.

To display an asynchronous button, you can follow the same steps as in the previous section, with two adjustments:

• Assign an asynchronous command to the UICommand.Command property.
• Set the UICommand.AsyncDisplayMode property to Wait or WaitCancel to display the wait indicator.

MainViewModel.cs

var buttonApplyAsync = new UICommand(
    id: "applyAsync",
    caption: "Apply Async",
    command: new AsyncCommand<CancelEventArgs>(
        async cancelArgs => {
            try {
                await // Your asynchronous "Apply" method 
            }
            catch (Exception e) {
                // Process errors
                // ...
                cancelArgs.Cancel = true;
            }
        },
        // Disable the button if one of the fields is empty:
        cancelArgs => !string.IsNullOrEmpty(dialogViewModel.FirstName) && !string.IsNullOrEmpty(dialogViewModel.LastName)
    ),
    asyncDisplayMode: AsyncDisplayMode.Wait,
    isDefault: false,
    isCancel: false
);

MainViewModel.vb

Dim buttonApplyAsync = New UICommand(
    id:="applyAsync", 
    caption:="Apply Async", 
    command:=New AsyncCommand(Of CancelEventArgs)(Async Function(cancelArgs)
        Try
            Await ' Your asynchronous "Apply" method 
        Catch e As Exception
            ' Process errors
            ' ...
            cancelArgs.Cancel = True
        End Try
    End Function,
    ' Disable the button if one of the fields is empty:
    Function(cancelArgs) Not String.IsNullOrEmpty(dialogViewModel.FirstName) AndAlso Not String.IsNullOrEmpty(dialogViewModel.LastName)), 
    asyncDisplayMode:=AsyncDisplayMode.Wait, 
    isDefault:=False, 
    isCancel:=False
)

Refer to the following help topic for more information: Asynchronous Commands.

Use Custom Dialog Buttons

Use Any Control as a Dialog Button

You can define custom buttons in the dialog View and use these buttons instead of standard dialog buttons:

1. Define custom buttons in the DialogView:

   MainWindow.xaml

   <dx:DialogService.ViewTemplate>
       <DataTemplate>
           <local:DialogView/>
       </DataTemplate>
   </dx:DialogService.ViewTemplate>
   

   DialogView.xaml

   <Grid>
       <Grid.RowDefinitions>
           <RowDefinition />
           <RowDefinition Height="Auto"/>
       </Grid.RowDefinitions>
   
       <StackPanel Orientation="Vertical" VerticalAlignment="Center" HorizontalAlignment="Center">
           <StackPanel Orientation="Horizontal">
               <TextBlock Text="First Name: " VerticalAlignment="Center"/>
               <dxe:TextEdit Text="{Binding FirstName}" Width="100"/>
           </StackPanel>
           <StackPanel Orientation="Horizontal" >
               <TextBlock Text="First Name: " VerticalAlignment="Center"/>
               <dxe:TextEdit Text="{Binding LastName}" Width="100"/>
           </StackPanel>
       </StackPanel>
   
       <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" Margin="5" Grid.Row="1">
           <dx:SimpleButton Glyph="{dx:DXImage 'SvgImages/Icon Builder/Actions_CheckCircled.svg'}" 
                            GlyphHeight="50" GlyphWidth="50" 
                            Command="{Binding ApplyCommand}"/>
           <dx:SimpleButton Glyph="{dx:DXImage 'SvgImages/Icon Builder/Actions_DeleteCircled.svg'}" 
                            GlyphHeight="50" GlyphWidth="50" 
                            Command="{Binding CancelCommand}"/>
       </StackPanel>
   </Grid>
   

2. Attach the CurrentDialogService to the DialogView to access the dialog window from its View Model:

   DialogView.xaml

   <UserControl ...
               x:Class="DialogServiceExample.DialogView"
               xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
               xmlns:dxmvvm="http://schemas.devexpress.com/winfx/2008/xaml/mvvm">
       <dxmvvm:Interaction.Behaviors>
           <dx:CurrentDialogService/>
       </dxmvvm:Interaction.Behaviors>
   

3. Create commands that use the CurrentDialogService.Close method to close the dialog window and specify the dialog result:

   DialogViewModel.cs

   public class DialogViewModel : ViewModelBase {
       // ...
       protected ICurrentDialogService CurrentDialogService { get { return GetService<ICurrentDialogService>(); } }
   
       [Command]
       public void Apply() {
           CurrentDialogService.Close(MessageResult.OK);
       }
   
       [Command]
       public void Cancel() {
           CurrentDialogService.Close(MessageResult.Cancel);
   
       }
   }
   

   DialogViewModel.vb

   Public Class DialogViewModel
       Inherits ViewModelBase
       ' ...
       Protected ReadOnly Property CurrentDialogService As ICurrentDialogService
           Get
               Return GetService(Of ICurrentDialogService)()
           End Get
       End Property
   
       <Command>
       Public Sub Apply()
           CurrentDialogService.Close(MessageResult.OK)
       End Sub
   
       <Command>
       Public Sub Cancel()
           CurrentDialogService.Close(MessageResult.Cancel)
       End Sub
   End Class
   

   Refer to the following help topic for more information on the CurrentDialogService.Close method overloads: CurrentDialogService.

4. Hide the standard dialog buttons:

   MainWindow.xaml

   xmlns:dxi="http://schemas.devexpress.com/winfx/2008/xaml/core/internal"
   
   <dx:DialogService.DialogStyle>
       <Style TargetType="Window">
           <Setter Property="Height" Value="200"/>
           <Setter Property="Width" Value="300"/>
           <Setter Property="dxi:ThemedWindowOptions.UseCustomDialogFooter" Value="True"/>
       </Style>
   </dx:DialogService.DialogStyle>
   

View Example: Close an Opened Dialog and Specify the Dialog Result

Use the Built-in Dialog Button Type to Create Customized Buttons

Dialog buttons are objects of the ThemedWindowDialogButton class. You can add these elements to the dialog View and specify their position and appearance:

1. Create ThemedWindowDialogButton objects, specify their properties, and place these buttons in the ThemedWindowDialogButtonsControl container:

   DialogView.xaml

   <Grid>
       <Grid.RowDefinitions>
           <RowDefinition Height="Auto"/>
           <RowDefinition />
       </Grid.RowDefinitions>
   
       <StackPanel Grid.Row="1" Orientation="Vertical" VerticalAlignment="Center" HorizontalAlignment="Center">
           <StackPanel Orientation="Horizontal">
               <TextBlock Text="First Name: " VerticalAlignment="Center"/>
               <dxe:TextEdit Text="{Binding FirstName, UpdateSourceTrigger=PropertyChanged}" Width="100"/>
           </StackPanel>
           <StackPanel Orientation="Horizontal" >
               <TextBlock Text="Last Name: " VerticalAlignment="Center"/>
               <dxe:TextEdit Text="{Binding LastName, UpdateSourceTrigger=PropertyChanged}" Width="100" Margin="1,0,0,0"/>
           </StackPanel>
       </StackPanel>
   
       <dx:ThemedWindowDialogButtonsControl Grid.Row="1" HorizontalAlignment="Center" VerticalAlignment="Top">
           <dx:ThemedWindowDialogButton UICommand="{Binding UICommandApply}"
                                        Content="{Binding UICommand.Caption, RelativeSource={RelativeSource Self}}"
                                        Glyph="{Binding UICommand.Glyph, RelativeSource={RelativeSource Self}}"
                                        Command="{Binding UICommand.Command, RelativeSource={RelativeSource Self}}"/>
           <dx:ThemedWindowDialogButton UICommand="{Binding UICommandCancel}"
                                        Content="{Binding UICommand.Caption, RelativeSource={RelativeSource Self}}"
                                        Glyph="{Binding UICommand.Glyph, RelativeSource={RelativeSource Self}}"
                                        Command="{Binding UICommand.Command, RelativeSource={RelativeSource Self}}"/>
       </dx:ThemedWindowDialogButtonsControl>
   </Grid>
   

   The ThemedWindowDialogButton class contains DialogResult and UICommand properties. These properties allow you to specify the value returned by the ShowDialog method when a user clicks the button.

2. Hide the standard dialog buttons:

   MainWindow.xaml

   xmlns:dxi="http://schemas.devexpress.com/winfx/2008/xaml/core/internal"
   
   <dx:DialogService.DialogStyle>
       <Style TargetType="Window">
           <Setter Property="Height" Value="200"/>
           <Setter Property="Width" Value="300"/>
           <Setter Property="dxi:ThemedWindowOptions.UseCustomDialogFooter" Value="True"/>
       </Style>
   </dx:DialogService.DialogStyle>
   

View Example: Customize Dialog Buttons

Execute an Action when a User Closes the Dialog

You can use the CurrentDialogService.ClosingCommand property to process the close dialog operation.

1. Create a command that is executed when a user closes the dialog. The following code sample displays a confirmation message when a user clicks the dialog window’s Close button (X):

   DialogViewModel.cs

   public class DialogViewModel : ViewModelBase {
       // ...
       protected ICurrentDialogService CurrentDialogService { get { return GetService<ICurrentDialogService>(); } }
       protected IMessageBoxService MessageBoxService { get { return GetService<IMessageBoxService>(); } }
   
       [Command]
       public void DialogClosing(CancelEventArgs args) {
           var dialogResult = (CurrentDialogService as CurrentDialogService).ActualWindow.DialogResult;
           if (dialogResult != null) return;
           var result = MessageBoxService.ShowMessage(
               caption: "Close",
               messageBoxText: "Do you want to discard changes?",
               button: MessageButton.YesNo,
               defaultResult: MessageResult.No,
               icon: MessageIcon.Question
           );
           if (result == MessageResult.Yes) {
               CurrentDialogService.Close(MessageResult.Cancel);
           } else {
               args.Cancel = true;
           }
       }
   }
   

   DialogViewModel.vb

   Public Class DialogViewModel
       Inherits ViewModelBase
       ' ...
       Protected ReadOnly Property CurrentDialogService As ICurrentDialogService
           Get
               Return GetService(Of ICurrentDialogService)()
           End Get
       End Property
   
       Protected ReadOnly Property MessageBoxService As IMessageBoxService
           Get
               Return GetService(Of IMessageBoxService)()
           End Get
       End Property
   
       <Command>
       Public Sub DialogClosing(ByVal args As CancelEventArgs)
           Dim dialogResult = (TryCast(CurrentDialogService, CurrentDialogService)).ActualWindow.DialogResult
           If dialogResult IsNot Nothing Then Return
           Dim result = MessageBoxService.ShowMessage(caption:="Close", messageBoxText:="Do you want to discard changes?", button:=MessageButton.YesNo, defaultResult:=MessageResult.No, icon:=MessageIcon.Question)
   
           If result = MessageResult.Yes Then
               CurrentDialogService.Close(MessageResult.Cancel)
           Else
               args.Cancel = True
           End If
       End Sub
   End Class
   

   The ActualWindow.DialogResult property returns the following values based on the MessageResult enumeration:

   • true if the ShowDialog method returns OK and Yes values.
   • false if the ShowDialog method returns Cancel, No, and None values or if the dialog result is of the UICommand type.
   • null if the dialog window is closed without parameters (for example, a user clicks the window’s Close button).

2. Bind the CurrentDialogService.ClosingCommand property to the created command:

   DialogView.xaml

   <dxmvvm:Interaction.Behaviors>
       <dx:CurrentDialogService ClosingCommand="{Binding DialogClosingCommand}"/>
       <dx:DXMessageBoxService/>
   </dxmvvm:Interaction.Behaviors>
   

View Example: Customize Dialog Buttons