回答編集履歴

- MVVMにこだわらないのであれば、

- ```xaml

- <Window

- x:Class="WpfApp1.SubWindow"

- xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

- xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

- xmlns:local="clr-namespace:WpfApp1"

- Title="SubWindow"

- Width="800"

- Height="450">

- <Window.DataContext>

- <local:SubViewModel />

- </Window.DataContext>

- <Grid>

- <Grid.RowDefinitions>

- <RowDefinition />

- <RowDefinition />

- </Grid.RowDefinitions>

- <TextBox Text="{Binding Text}" />

- <Grid Grid.Row="1">

- <Grid.ColumnDefinitions>

- <ColumnDefinition />

- <ColumnDefinition />

- </Grid.ColumnDefinitions>

- <Button Content="Cancel" IsCancel="True" />

- <Button

- Grid.Column="1"

- Command="{Binding DoSomethingCommand}"

- CommandParameter="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}}"

- Content="OK"

- IsDefault="True" />

- </Grid>

- </Grid>

- </Window>

- ```

-

- ```C#

- using System.Windows;

- using Prism.Commands;

-

- namespace WpfApp1

- {

- public class SubViewModel

- {

- public string Text { get; set; }

- public DelegateCommand<Window> DoSomethingCommand { get; }

-

- public SubViewModel()

- {

- DoSomethingCommand = new DelegateCommand<Window>((w) =>

- {

- System.Diagnostics.Debug.WriteLine("DoSomethigCommand");

-

- if(string.IsNullOrEmpty(Text))

- {

- MessageBox.Show("何か入力してください。");

- }

- else

- {

- w.DialogResult = true;

- }

- });

- }

- }

- }

- ```

- こんな感じでどうでしょうか。

-

- ---

-

- 実際には入力値はもっとあってそれぞれ検証したいのであれば`INotifyDataErrorInfo`等を実装し、エラーがあればボタンを押せなくするのがきれいかもしれません。

-

- ```xaml

- <Window

- x:Class="WpfApp1.SubWindow"

- xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

- xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

- xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"

- xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"

- xmlns:local="clr-namespace:WpfApp1"

- Name="SubWnd"

- Title="SubWindow"

- Width="800"

- Height="450">

- <Window.Resources>

- <ControlTemplate x:Key="ValidationTemplate">

- <StackPanel>

- <ItemsControl HorizontalAlignment="Right" ItemsSource="{Binding AdornedElement.(Validation.Errors), ElementName=validationTarget}">

- <ItemsControl.ItemTemplate>

- <DataTemplate>

- <TextBlock Foreground="Red" Text="{Binding ErrorContent}" />

- </DataTemplate>

- </ItemsControl.ItemTemplate>

- </ItemsControl>

- <AdornedElementPlaceholder x:Name="validationTarget" />

- </StackPanel>

- </ControlTemplate>

- </Window.Resources>

- <Window.DataContext>

- <local:SubViewModel />

- </Window.DataContext>

- <DockPanel>

- <StackPanel

- HorizontalAlignment="Right"

- DockPanel.Dock="Bottom"

- Orientation="Horizontal">

- <Button

- MinWidth="80"

- Margin="5"

- Command="{Binding DoSomethingCommand}"

- Content="OK">

- <i:Interaction.Triggers>

- <i:EventTrigger EventName="Click">

- <ei:ChangePropertyAction

- PropertyName="DialogResult"

- TargetObject="{Binding ElementName=SubWnd}"

- Value="True" />

- </i:EventTrigger>

- </i:Interaction.Triggers>

- </Button>

- <Button

- MinWidth="80"

- Margin="5"

- Content="Cancel"

- IsCancel="True" />

- </StackPanel>

-

- <StackPanel>

- <HeaderedContentControl Margin="5" Header="Text1">

- <TextBox Text="{Binding Text1, UpdateSourceTrigger=PropertyChanged}" Validation.ErrorTemplate="{StaticResource ValidationTemplate}" />

- </HeaderedContentControl>

- <HeaderedContentControl Margin="5" Header="Text2">

- <TextBox Text="{Binding Text2, UpdateSourceTrigger=PropertyChanged}" Validation.ErrorTemplate="{StaticResource ValidationTemplate}" />

- </HeaderedContentControl>

- <HeaderedContentControl Margin="5" Header="Text3">

- <TextBox Text="{Binding Text3, UpdateSourceTrigger=PropertyChanged}" Validation.ErrorTemplate="{StaticResource ValidationTemplate}" />

- </HeaderedContentControl>

- </StackPanel>

- </DockPanel>

- </Window>

- ```

-

- ```C#

- using System;

- using System.Collections;

- using System.Collections.Generic;

- using System.ComponentModel;

- using System.ComponentModel.DataAnnotations;

- using System.Linq;

- using System.Runtime.CompilerServices;

- using Prism.Commands;

- using Prism.Mvvm;

-

- namespace WpfApp1

- {

- public class SubViewModel : BindableBase, INotifyDataErrorInfo

- {

- [Required(ErrorMessage = "何か入力してください。")]

- public string Text1 { get => _Text1; set => SetProperty(ref _Text1, value); }

- private string _Text1;

-

- [MinLength(10, ErrorMessage = "10文字以上入力してください。")]

- public string Text2 { get => _Text2; set => SetProperty(ref _Text2, value); }

- private string _Text2;

-

- [RegularExpression("[a-z]+", ErrorMessage = "a-zの文字列を入力してください。")]

- public string Text3 { get => _Text3; set => SetProperty(ref _Text3, value); }

- private string _Text3;

-

- public DelegateCommand DoSomethingCommand { get; }

-

-

- public SubViewModel()

- {

- errorsContainer = new ErrorsContainer<string>(x => ErrorsChanged?.Invoke(this, new DataErrorsChangedEventArgs(x)));

-

- Text1 = ""; // ""に深い意味はない。初期値nullから動かしてValidatorを通してるだけ

- Text2 = "";

- Text3 = "A";

-

- DoSomethingCommand = new DelegateCommand(

- () => System.Diagnostics.Debug.WriteLine("DoSomethigCommand"),

- () => !HasErrors)

- .ObservesProperty(() => HasErrors);

- }

-

-

- #region INotifyDataErrorInfo

- private readonly ErrorsContainer<string> errorsContainer;

- public bool HasErrors => errorsContainer.HasErrors;

- public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;

- protected override bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)

- {

- if(!base.SetProperty(ref storage, value, propertyName)) return false;

-

- var context = new ValidationContext(this) { MemberName = propertyName };

- var errors = new List<ValidationResult>();

- if(!Validator.TryValidateProperty(value, context, errors))

- {

- errorsContainer.SetErrors(propertyName, errors.Select(x => x.ErrorMessage));

- }

- else

- {

- errorsContainer.ClearErrors(propertyName);

- }

- RaisePropertyChanged(nameof(HasErrors));

- return true;

- }

- public IEnumerable GetErrors(string propertyName) => errorsContainer.GetErrors(propertyName);

- #endregion

- }