WPF中使用ValidationRule自定義驗證規則

本文主要是展示在 WPF 中使用 ValidationRule 自定義驗證規則，然后通過 Behavior 傳遞到 ViewModel 中，在 ViewModel 中對錯誤資訊統一回應，

1、自定義驗證規則類

這里自定義兩個驗證規則類，分別用于驗證 “用戶名”輸入不可為空、“郵箱”輸入值需滿足格式要求，

兩個類需要繼承 ValidationRule 類，ValidationRule 是抽象類，需要具體實作 Validate 方法，代碼如下：

NotEmptyValidationRule.cs

using System.Globalization;
using System.Windows.Controls;

namespace MyValidationRuleDemo.MyValidationRules
{
    public class NotEmptyValidationRule : ValidationRule
    {
        public override ValidationResult Validate(object value, CultureInfo cultureInfo)
        {
            return string.IsNullOrWhiteSpace((value ?? "").ToString()) ?
                new ValidationResult(false, "不能為空") : new ValidationResult(true, null);
        }
    }
}

EmailValidationRule.cs

using System.Globalization;
using System.Text.RegularExpressions;
using System.Windows.Controls;

namespace MyValidationRuleDemo.MyValidationRules
{
    public class EmailValidationRule : ValidationRule
    {
        public override ValidationResult Validate(object value, CultureInfo cultureInfo)
        {
            Regex emailRegex = new Regex("^\\s*([A-Za-z0-9_-]+(\\.\\w+)*@(\\w+\\.)+\\w{2,5})\\s*$");
            string str = (value ?? "").ToString();
            if (!string.IsNullOrWhiteSpace(str))
            {
                if (!emailRegex.IsMatch(str))
                {
                    return new ValidationResult(false, "郵箱地址錯誤！");
                }
            }
            return new ValidationResult(true, null);
        }
    }
}

2、在前端頁面中添加驗證

在前端頁面中需要進行以下操作：

添加自定義的 ValidationRule 所有的命名空間；

xmlns:valRules="clr-namespace:MyValidationRuleDemo.MyValidationRules"

在需要驗證的控制元件上的 Binding 上對應的自定義驗證規則類；

<Binding.ValidationRules>
	<valRules:EmailValidationRule />
</Binding.ValidationRules>

具體代碼如下：

<Window
    x:
    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:MyValidationRuleDemo"
    xmlns:valRules="clr-namespace:MyValidationRuleDemo.MyValidationRules"
    Title="MainWindow"
    Width="800"
    Height="400"
    mc:Ignorable="d">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition />
            <RowDefinition />
        </Grid.RowDefinitions>
        <StackPanel
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            Orientation="Horizontal">
            <Label
                Content="用戶名:"
                Margin="0,0,10,0"
                FontSize="20" />
            <TextBox Width="200" Height="30">
                <TextBox.Text>
                    <Binding
                        Path="UserName"
                        UpdateSourceTrigger="PropertyChanged">
                        <Binding.ValidationRules>
                            <valRules:NotEmptyValidationRule />
                        </Binding.ValidationRules>
                    </Binding>
                </TextBox.Text>
            </TextBox>
        </StackPanel>
        <StackPanel Grid.Row="1"
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            Orientation="Horizontal">
            <Label
                Content="郵箱:"
                Margin="0,0,10,0"
                FontSize="20" />
            <TextBox Width="200" Height="30">
                <TextBox.Text>
                    <Binding
                        Path="UserEmail"
                        UpdateSourceTrigger="PropertyChanged">
                        <Binding.ValidationRules>
                            <valRules:EmailValidationRule />
                        </Binding.ValidationRules>
                    </Binding>
                </TextBox.Text>
            </TextBox>
        </StackPanel>
        <Button Grid.Row="2"
            Content="提交"
            Width="200"
            Height="30"
            Margin="0,20,0,0" />
    </Grid>
</Window>

前端頁面系結的驗證引數具體如下：

using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;

namespace MyValidationRuleDemo.ViewModel
{
    public class MainViewModel : ViewModelBase
    {
        public MainViewModel()
        {
        }

        private string userName;
        /// <summary>
        /// 用戶名
        /// </summary>
        public string UserName
        {
            get { return userName; }
            set { userName = value; RaisePropertyChanged(); }
        }

        private string userEmail;
        /// <summary>
        /// 用戶郵件
        /// </summary>
        public string UserEmail
        {
            get { return userEmail; }
            set { userEmail = value; RaisePropertyChanged(); }
        }

    }
}

此時，自定義的驗證規則已經生效，當頁面輸入不符合規則時，會默認的紅框進行標記，這是 WPF 中默認的效果，效果如下圖：

ValidationRule01

3、使用 Behavior 自定義回應效果

上面雖然已經在頁面上有了基本的錯誤回應效果，但是效果過于單一，這里我們在這里使用 Behavior 監聽 Validation.Error 事件，并將錯誤資訊傳遞到 ViewModel 中進行統一進行錯誤提醒，同時，在 MVMM 架構中將錯誤資訊傳遞到 ViewModel 中進行統一處理，在有需要的時候也有利于業務邏輯處理，

3.1、實作步驟

進行以上操作需要進行以下步驟：

開啟驗證錯誤的通知屬性 NotifyOnValidationError="True" ，這樣就可以產生 Validation.Error 事件，

<TextBox Width="200" Height="30">
    <TextBox.Text>
        <Binding
                 Path="UserEmail"
                 NotifyOnValidationError="True"
                 UpdateSourceTrigger="PropertyChanged">
            <Binding.ValidationRules>
                <valRules:EmailValidationRule />
            </Binding.ValidationRules>
        </Binding>
    </TextBox.Text>
</TextBox>

通過自定義的 ValidationExceptionBehavior 繼承于 Behavior，用于監聽 Validation.Error 的錯誤事件，

protected override void OnAttached()
{
    //添加 Validation.Error 事件監聽
    this.AssociatedObject.AddHandler(Validation.ErrorEvent, new EventHandler<ValidationErrorEventArgs>(OnValidationError));
}

View 中添加 Behavior；

<i:Interaction.Behaviors>
    <local:ValidationExceptionBehavior />
</i:Interaction.Behaviors>

在 ValidationExceptionBehavior 中通過 AssociatedObject 的DataContext 獲取到關聯當前View的ViewModel，并將錯誤提示統一收集到 ViewModel 的 ErrorList ，

private void OnValidationError(Object sender, ValidationErrorEventArgs e)
{
    MainViewModel mainModel = null;
    if (AssociatedObject.DataContext is MainViewModel)
    {
        mainModel = this.AssociatedObject.DataContext as MainViewModel;
    }
    if (mainModel == null) return;

    //OriginalSource 觸發事件的元素
    var element = e.OriginalSource as UIElement;
    if (element == null) return;

    //ValidationErrorEventAction.Added  表示新產生的行為
    if (e.Action == ValidationErrorEventAction.Added)
    {
        mainModel.ErrorList.Add(e.Error.ErrorContent.ToString());
    }
    else if (e.Action == ValidationErrorEventAction.Removed) //ValidationErrorEventAction.Removed  該行為被移除，即代表驗證通過
    {
        mainModel.ErrorList.Remove(e.Error.ErrorContent.ToString());
    }
}

在 View 中按鈕系結的 Command 中統一處理 ErrorList；

public RelayCommand SaveCommand { get; set; }
public MainViewModel()
{
    SaveCommand = new RelayCommand(() =>
                                   {
                                       StringBuilder sb = new StringBuilder();
                                       foreach (var error in ErrorList)
                                       {
                                           sb.Append(error + "\r\n");
                                       }
                                       MessageBox.Show(sb.ToString());
                                   });
}

開啟 ValidationRule 的屬性 ValidatesOnTargetUpdated="True"，否則在加載頁面后，文本框中未輸入值則不會進行驗證，
```
<Binding.ValidationRules>
    <valRules:EmailValidationRule ValidatesOnTargetUpdated="True" />
</Binding.ValidationRules>
```

3.2、具體代碼

完整代碼如下：

ValidationExceptionBehavior.cs

using MyValidationRuleDemo.ViewModel;
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;

namespace MyValidationRuleDemo
{
    public class ValidationExceptionBehavior : Behavior<FrameworkElement>
    {

        protected override void OnAttached()
        {
            //添加 Validation.Error 事件監聽
            this.AssociatedObject.AddHandler(Validation.ErrorEvent, new EventHandler<ValidationErrorEventArgs>(OnValidationError));
        }

        private void OnValidationError(Object sender, ValidationErrorEventArgs e)
        {
            MainViewModel mainModel = null;
            if (AssociatedObject.DataContext is MainViewModel)
            {
                mainModel = this.AssociatedObject.DataContext as MainViewModel;
            }
            if (mainModel == null) return;

            //OriginalSource 觸發事件的元素
            var element = e.OriginalSource as UIElement;
            if (element == null) return;

            //ValidationErrorEventAction.Added  表示新產生的行為
            if (e.Action == ValidationErrorEventAction.Added)
            {
                mainModel.ErrorList.Add(e.Error.ErrorContent.ToString());
            }
            else if (e.Action == ValidationErrorEventAction.Removed) //ValidationErrorEventAction.Removed  該行為被移除，即代表驗證通過
            {
                mainModel.ErrorList.Remove(e.Error.ErrorContent.ToString());
            }
        }

        protected override void OnDetaching()
        {
            //移除 Validation.Error 事件監聽
            this.AssociatedObject.RemoveHandler(Validation.ErrorEvent, new EventHandler<ValidationErrorEventArgs>(OnValidationError));
        }
    }
}

MainView.xaml

<Window
    x:
    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:MyValidationRuleDemo"
    xmlns:valRules="clr-namespace:MyValidationRuleDemo.MyValidationRules"
    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    Title="MainWindow"
    Width="800"
    Height="400"
    mc:Ignorable="d">
    <i:Interaction.Behaviors>
        <local:ValidationExceptionBehavior />
    </i:Interaction.Behaviors>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition />
            <RowDefinition />
        </Grid.RowDefinitions>
        <StackPanel
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            Orientation="Horizontal">
            <Label
                Content="用戶名:"
                Margin="0,0,10,0"
                FontSize="20" />
            <TextBox Width="200" Height="30">
                <TextBox.Text>
                    <Binding
                        Path="UserName"
                        NotifyOnValidationError="True"
                        UpdateSourceTrigger="PropertyChanged">
                        <Binding.ValidationRules>
                            <valRules:NotEmptyValidationRule ValidatesOnTargetUpdated="True" />
                        </Binding.ValidationRules>
                    </Binding>
                </TextBox.Text>
            </TextBox>
        </StackPanel>
        <StackPanel Grid.Row="1"
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            Orientation="Horizontal">
            <Label
                Content="郵箱:"
                Margin="0,0,10,0"
                FontSize="20" />
            <TextBox Width="200" Height="30">
                <TextBox.Text>
                    <Binding
                        Path="UserEmail"
                        NotifyOnValidationError="True"
                        UpdateSourceTrigger="PropertyChanged">
                        <Binding.ValidationRules>
                            <valRules:EmailValidationRule ValidatesOnTargetUpdated="True" />
                        </Binding.ValidationRules>
                    </Binding>
                </TextBox.Text>
            </TextBox>
        </StackPanel>
        <Button Grid.Row="2"
            Content="提交"
            Command="{Binding SaveCommand}"
            Width="200"
            Height="30"
            Margin="0,20,0,0" />
    </Grid>
</Window>

MainViewModel.cs

using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;
using System.Collections.ObjectModel;
using System.Text;
using System.Windows;

namespace MyValidationRuleDemo.ViewModel
{
    public class MainViewModel : ViewModelBase
    {
        public MainViewModel()
        {
            SaveCommand = new RelayCommand(() =>
            {
                StringBuilder sb = new StringBuilder();
                foreach (var error in ErrorList)
                {
                    sb.Append(error + "\r\n");
                }
                MessageBox.Show(sb.ToString());
            });
        }

        public RelayCommand SaveCommand { get; set; }

        private string userName;
        /// <summary>
        /// 用戶名
        /// </summary>
        public string UserName
        {
            get { return userName; }
            set { userName = value; RaisePropertyChanged(); }
        }

        private string userEmail;
        /// <summary>
        /// 用戶郵件
        /// </summary>
        public string UserEmail
        {
            get { return userEmail; }
            set { userEmail = value; RaisePropertyChanged(); }
        }

        private ObservableCollection<string> errorList = new ObservableCollection<string>();
        /// <summary>
        /// 錯誤提示
        /// </summary>
        public ObservableCollection<string> ErrorList
        {
            get { return errorList; }
            set { errorList = value; RaisePropertyChanged(); }
        }

    }
}

3.3、效果展示

ValidationRule02

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標籤：WPF

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