MVVMLight怎么綁定在表單驗(yàn)證上

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表單驗(yàn)證是MVVM體系中的重要一塊。而綁定除了推動(dòng) Model-View-ViewModel (MVVM) 模式松散耦合 邏輯、數(shù)據(jù) 和 UI定義 的關(guān)系之外，還為業(yè)務(wù)數(shù)據(jù)驗(yàn)證方案提供強(qiáng)大而靈活的支持。

WPF 中的數(shù)據(jù)綁定機(jī)制包括多個(gè)選項(xiàng)，可用于在創(chuàng)建可編輯視圖時(shí)校驗(yàn)輸入數(shù)據(jù)的有效性。

常見的表單驗(yàn)證機(jī)制有如下幾種：

驗(yàn)證交互的關(guān)系模式如圖：

我們?cè)谑褂?WPF 中的數(shù)據(jù)綁定來呈現(xiàn)業(yè)務(wù)數(shù)據(jù)時(shí)，通常會(huì)使用 Binding 對(duì)象在目標(biāo)控件的單個(gè)屬性與數(shù)據(jù)源對(duì)象屬性之間提供數(shù)據(jù)管道。

如果要使得綁定驗(yàn)證有效，首先需要進(jìn)行 TwoWay 數(shù)據(jù)綁定。這表明，除了從源屬性流向目標(biāo)屬性以進(jìn)行顯示的數(shù)據(jù)之外，編輯過的數(shù)據(jù)也會(huì)從目標(biāo)流向源。

這就是偉大的雙向數(shù)據(jù)綁定的精髓，所以在MVVM中做數(shù)據(jù)校驗(yàn)，會(huì)容易的多。

當(dāng) TwoWay 數(shù)據(jù)綁定中輸入或修改數(shù)據(jù)時(shí)，將啟動(dòng)以下工作流：

綁定目標(biāo)向綁定源發(fā)送數(shù)據(jù)更新的請(qǐng)求，而綁定源則對(duì)數(shù)據(jù)進(jìn)行驗(yàn)證，并根據(jù)不同的驗(yàn)證機(jī)制進(jìn)行反饋。 

下面我們用實(shí)例來對(duì)比下這幾種驗(yàn)證機(jī)制，在此之前，我們先做一個(gè)事情，就是寫一個(gè)錯(cuò)誤觸發(fā)的樣式，來保證錯(cuò)誤觸發(fā)的時(shí)候直接清晰的向用戶反饋出去。

我們新建一個(gè)資源字典文件，命名為TextBox.xaml，下面這個(gè)是資源字典文件的內(nèi)容，目標(biāo)類型是TextBoxBase基礎(chǔ)的控件，如TextBox和RichTextBox.

代碼比較簡單，注意標(biāo)紅的內(nèi)容，設(shè)計(jì)一個(gè)紅底白字的提示框，當(dāng)源屬性觸發(fā)錯(cuò)誤驗(yàn)證的時(shí)候，把驗(yàn)證對(duì)象集合中的錯(cuò)誤內(nèi)容顯示出來。

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
   <Style x:Key="{x:Type TextBoxBase}" TargetType="{x:Type TextBoxBase}" BasedOn="{x:Null}">
       <Setter Property="BorderThickness" Value="1"/>
       <Setter Property="Padding" Value="2,1,1,1"/>
       <Setter Property="AllowDrop" Value="true"/>
       <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
       <Setter Property="ScrollViewer.PanningMode" Value="VerticalFirst"/>
       <Setter Property="Stylus.IsFlicksEnabled" Value="False"/>
       <Setter Property="SelectionBrush" Value="{DynamicResource Accent}" />
       <Setter Property="Validation.ErrorTemplate">
           <Setter.Value>
               <ControlTemplate>
                   <StackPanel Orientation="Horizontal">
                       <Border BorderThickness="1" BorderBrush="#FFdc000c" VerticalAlignment="Top">
                           <Grid>
                               <AdornedElementPlaceholder x:Name="adorner" Margin="-1"/>
                           </Grid>
                       </Border>
                       <Border x:Name="errorBorder" Background="#FFdc000c" Margin="8,0,0,0"
                               Opacity="0" CornerRadius="0"
                               IsHitTestVisible="False"
                               MinHeight="24" >
                           <TextBlock Text="{Binding ElementName=adorner, Path=AdornedElement.(Validation.Errors)[0].ErrorContent}"
                                      Foreground="White" Margin="8,2,8,3" TextWrapping="Wrap" VerticalAlignment="Center"/>
                       </Border>
                   </StackPanel>
                   <ControlTemplate.Triggers>
                       <DataTrigger Value="True">
                           <DataTrigger.Binding>
                               <Binding ElementName="adorner" Path="AdornedElement.IsKeyboardFocused" />
                           </DataTrigger.Binding>
                           <DataTrigger.EnterActions>
                               <BeginStoryboard x:Name="fadeInStoryboard">
                                   <Storyboard>
                                       <DoubleAnimation Duration="00:00:00.15"
                                                        Storyboard.TargetName="errorBorder"
                                                        Storyboard.TargetProperty="Opacity"
                                                        To="1"/>
                                   </Storyboard>
                               </BeginStoryboard>
                           </DataTrigger.EnterActions>
                           <DataTrigger.ExitActions>
                               <StopStoryboard BeginStoryboardName="fadeInStoryboard"/>
                               <BeginStoryboard x:Name="fadeOutStoryBoard">
                                   <Storyboard>
                                       <DoubleAnimation Duration="00:00:00"
                                                        Storyboard.TargetName="errorBorder"
                                                        Storyboard.TargetProperty="Opacity"
                                                        To="0"/>
                                   </Storyboard>
                               </BeginStoryboard>
                           </DataTrigger.ExitActions>
                       </DataTrigger>
                   </ControlTemplate.Triggers>
               </ControlTemplate>
           </Setter.Value>
       </Setter>
       <Setter Property="Template">
           <Setter.Value>
               <ControlTemplate TargetType="{x:Type TextBoxBase}">
                   <Border x:Name="Bd"
                           BorderThickness="{TemplateBinding BorderThickness}"
                           BorderBrush="{TemplateBinding BorderBrush}"
                           Background="{TemplateBinding Background}"
                           Padding="{TemplateBinding Padding}"
                           SnapsToDevicePixels="true">
                       <ScrollViewer x:Name="PART_ContentHost" RenderOptions.ClearTypeHint="Enabled"
                                     SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                   </Border>
                   <ControlTemplate.Triggers>
                       <Trigger Property="IsEnabled" Value="false">
                           <Setter Property="Foreground" Value="{DynamicResource InputTextDisabled}"/>
                       </Trigger>
                       <Trigger Property="IsReadOnly" Value="true">
                           <Setter Property="Foreground" Value="{DynamicResource InputTextDisabled}"/>
                       </Trigger>
                       <Trigger Property="IsFocused" Value="true">
                           <Setter TargetName="Bd" Property="BorderBrush" Value="{DynamicResource Accent}" />
                       </Trigger>
                       <MultiTrigger>
                           <MultiTrigger.Conditions>
                               <Condition Property="IsReadOnly" Value="False"/>
                               <Condition Property="IsEnabled" Value="True"/>
                               <Condition Property="IsMouseOver" Value="True"/>
                           </MultiTrigger.Conditions>
                           <Setter Property="Background" Value="{DynamicResource InputBackgroundHover}"/>
                           <Setter Property="BorderBrush" Value="{DynamicResource InputBorderHover}"/>
                           <Setter Property="Foreground" Value="{DynamicResource InputTextHover}"/>
                       </MultiTrigger>
                   </ControlTemplate.Triggers>
               </ControlTemplate>
           </Setter.Value>
       </Setter>
   </Style>
   <Style BasedOn="{StaticResource {x:Type TextBoxBase}}" TargetType="{x:Type TextBox}">
   </Style>
   <Style BasedOn="{StaticResource {x:Type TextBoxBase}}" TargetType="{x:Type RichTextBox}">
   </Style>
</ResourceDictionary>

  然后在App.Xaml中全局注冊(cè)到整個(gè)應(yīng)用中。

 <Application x:Class="MVVMLightDemo.App" 
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
              StartupUri="View/BindingFormView.xaml" 
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
              d1p1:Ignorable="d" 
              xmlns:d1p1="http://schemas.openxmlformats.org/markup-compatibility/2006"
              xmlns:vm="clr-namespace:MVVMLightDemo.ViewModel"
              xmlns:Common="clr-namespace:MVVMLightDemo.Common">
   <Application.Resources>
     <ResourceDictionary>
             <ResourceDictionary.MergedDictionaries>
                 <ResourceDictionary Source="/MVVMLightDemo;component/Assets/TextBox.xaml" />
             </ResourceDictionary.MergedDictionaries>
             <vm:ViewModelLocator x:Key="Locator" d:IsDataSource="True" />
             <Common:IntegerToSex x:Key="IntegerToSex" d:IsDataSource="True" />
     </ResourceDictionary>
   </Application.Resources>
</Application>

 達(dá)到的效果如下：

下面詳細(xì)描述下這三種驗(yàn)證模式  

1、Exception 驗(yàn)證：

正如說明中描述的那樣，在具有綁定關(guān)系的源字段模型上做驗(yàn)證異常的引發(fā)并拋出，在View中的Xaml對(duì)象上設(shè)置 ExceptionValidationRule 屬性，響應(yīng)捕獲異常并顯示。

View代碼：

                <GroupBox Header="Exception 驗(yàn)證" Margin="10 10 10 10" DataContext="{Binding Source={StaticResource Locator},Path=ValidateException}" >
                     <StackPanel x:Name="ExceptionPanel" Orientation="Vertical" Margin="0,10,0,0" >
                         <StackPanel>
                             <Label Content="用戶名" Target="{Binding ElementName=UserNameEx}"/>
                             <TextBox x:Name="UserNameEx" Width="150">
                                 <TextBox.Text>
                                     <Binding Path="UserNameEx" UpdateSourceTrigger="PropertyChanged">
                                         <Binding.ValidationRules>
                                             <ExceptionValidationRule></ExceptionValidationRule>
                                         </Binding.ValidationRules>
                                     </Binding>
                                 </TextBox.Text>
                             </TextBox>
                         </StackPanel>
                     </StackPanel>
                 </GroupBox>

  ViewModel代碼：

   /// <summary>
    /// Exception 驗(yàn)證
    /// </summary>
    public class ValidateExceptionViewModel:ViewModelBase
    {
        public ValidateExceptionViewModel()
        {
        }
        private String userNameEx;
        /// <summary>
        /// 用戶名稱（不為空）
        /// </summary>
        public string UserNameEx
        {
            get
            {
                return userNameEx;
            }
            set
            {
                userNameEx = value;
                RaisePropertyChanged(() => UserNameEx);
                if (string.IsNullOrEmpty(value))
                {
                    throw new ApplicationException("該字段不能為空！");
                }
            }
        }

  結(jié)果如圖：

將驗(yàn)證失敗的信息直接拋出來，這無疑是最簡單粗暴的，實(shí)現(xiàn)也很簡單，但是只是針對(duì)單一源屬性進(jìn)行驗(yàn)證， 復(fù)用性不高。

而且在組合驗(yàn)證（比如同時(shí)需要驗(yàn)證非空和其他規(guī)則）情況下，會(huì)導(dǎo)致Model中寫過重過臃腫的代碼。

2、ValidationRule 驗(yàn)證：

通過繼承ValidationRule 抽象類，并重寫他的Validate方法來擴(kuò)展編寫我們需要的驗(yàn)證類。該驗(yàn)證類可以直接使用在我們需要驗(yàn)證的屬性。

View代碼：

 <GroupBox Header="ValidationRule 驗(yàn)證"  Margin="10 20 10 10" DataContext="{Binding Source={StaticResource Locator},Path=ValidationRule}" >
   <StackPanel x:Name="ValidationRulePanel" Orientation="Vertical" Margin="0,20,0,0">
       <StackPanel>
           <Label Content="用戶名" Target="{Binding ElementName=UserName}"/>
           <TextBox Width="150" >
               <TextBox.Text>
                   <Binding Path="UserName" UpdateSourceTrigger="PropertyChanged">
                   <Binding.ValidationRules>
                       <app:RequiredRule />
                   </Binding.ValidationRules>
               </Binding>
               </TextBox.Text>
           </TextBox>
       </StackPanel>
       <StackPanel>
           <Label Content="用戶郵箱" Target="{Binding ElementName=UserEmail}"/>
           <TextBox Width="150">
               <TextBox.Text>
                   <Binding Path="UserEmail" UpdateSourceTrigger="PropertyChanged">
                       <Binding.ValidationRules>
                           <app:EmailRule />
                       </Binding.ValidationRules>
                   </Binding>
               </TextBox.Text>
           </TextBox>
       </StackPanel>
   </StackPanel>
  </GroupBox>

 重寫兩個(gè)ValidationRule，代碼如下：

public class RequiredRule : ValidationRule
 {
     public override ValidationResult Validate(object value, CultureInfo cultureInfo)
     {
         if (value == null)
             return new ValidationResult(false, "該字段不能為空值！");
         if (string.IsNullOrEmpty(value.ToString()))
             return new ValidationResult(false, "該字段不能為空字符串！");
         return new ValidationResult(true, null);
     }
 }
 public class EmailRule : ValidationRule
 {
     public override ValidationResult Validate(object value, CultureInfo cultureInfo)
     {
         Regex emailReg = new Regex("^\\s*([A-Za-z0-9_-]+(\\.\\w+)*@(\\w+\\.)+\\w{2,5})\\s*$");

         if (!String.IsNullOrEmpty(value.ToString()))
         {
             if (!emailReg.IsMatch(value.ToString()))
             {
                 return new ValidationResult(false, "郵箱地址不準(zhǔn)確！");
             }
         }
         return new ValidationResult(true, null);
     }

 創(chuàng)建了兩個(gè)類，一個(gè)用于驗(yàn)證是否為空，一個(gè)用于驗(yàn)證是否符合郵箱地址標(biāo)準(zhǔn)格式。 

ViewModel代碼：

 public class ValidationRuleViewModel:ViewModelBase
    {
        public ValidationRuleViewModel()
        {
        }
        #region 屬性
        private String userName;
        /// <summary>
        /// 用戶名
        /// </summary>
        public String UserName
        {
            get { return userName; }
            set { userName = value; RaisePropertyChanged(()=>UserName); }
        }
        private String userEmail;
        /// <summary>
        /// 用戶郵件
        /// </summary>
        public String UserEmail
        {
            get { return userEmail; }
            set { userEmail = value;RaisePropertyChanged(()=>UserName);  }
        }
        #endregion

 結(jié)果如下：

 說明：相對(duì)來說，這種方式是比較不錯(cuò)的，獨(dú)立性、復(fù)用性都很好，從松散耦合角度來說也是比較恰當(dāng)?shù)摹?/p>

可以預(yù)先寫好一系列的驗(yàn)證規(guī)則類，視圖編碼人員可以根據(jù)需求直接使用這些驗(yàn)證規(guī)則，服務(wù)端無需額外的處理。

但是仍然有缺點(diǎn)，擴(kuò)展性差，如果需要個(gè)性化反饋消息也需要額外擴(kuò)展。不符合日益豐富的前端驗(yàn)證需求。

3、IDataErrorInfo 驗(yàn)證:

3.1、在綁定數(shù)據(jù)源對(duì)象上實(shí)現(xiàn) IDataErrorInfo 接口

3.2、在 Binding 對(duì)象上設(shè)置 ValidatesOnDataErrors 屬性

Binding 將調(diào)用從綁定數(shù)據(jù)源對(duì)象公開的 IDataErrorInfo API。如果從這些屬性調(diào)用返回非 null 或非空字符串，則將為該 Binding 設(shè)置驗(yàn)證錯(cuò)誤。

View代碼：

      <GroupBox Header="IDataErrorInfo 驗(yàn)證" Margin="10 20 10 10" DataContext="{Binding Source={StaticResource Locator},Path=BindingForm}" >
           <StackPanel x:Name="Form" Orientation="Vertical" Margin="0,20,0,0">
               <StackPanel>
                   <Label Content="用戶名" Target="{Binding ElementName=UserName}"/>
                   <TextBox Width="150" 
                        Text="{Binding UserName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" >
                   </TextBox>
               </StackPanel>

               <StackPanel>
                   <Label Content="性別" Target="{Binding ElementName=RadioGendeMale}"/>
                   <RadioButton Content="男" />
                   <RadioButton Content="女" Margin="8,0,0,0" />
               </StackPanel>
               <StackPanel>
                   <Label Content="生日" Target="{Binding ElementName=DateBirth}" />
                   <DatePicker x:Name="DateBirth" />
               </StackPanel>
               <StackPanel>
                   <Label Content="用戶郵箱" Target="{Binding ElementName=UserEmail}"/>
                   <TextBox Width="150" Text="{Binding UserEmail, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" />
               </StackPanel>
               <StackPanel>
                   <Label Content="用戶電話" Target="{Binding ElementName=UserPhone}"/>
                   <TextBox Width="150" Text="{Binding UserPhone, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" />
               </StackPanel>
           </StackPanel>
       </GroupBox>

 ViewModel代碼：

public class BindingFormViewModel :ViewModelBase, IDataErrorInfo
   {
       public BindingFormViewModel()
       {
       }
       #region 屬性
       private String userName;
       /// <summary>
       /// 用戶名
       /// </summary>
       public String UserName
       {
           get { return userName; }
           set { userName = value; }
       }
       private String userPhone;
       /// <summary>
       /// 用戶電話
       /// </summary>
       public String UserPhone
       {
           get { return userPhone; }
           set { userPhone = value; }
       }
       private String userEmail;
       /// <summary>
       /// 用戶郵件
       /// </summary>
       public String UserEmail
       {
           get { return userEmail; }
           set { userEmail = value; }
       }
       #endregion
       public String Error
       {
           get { return null; }
       }
       public String this[string columnName]
       {
           get
           {
               Regex digitalReg = new Regex(@"^[-]?[1-9]{8,11}\d*$|^[0]{1}$");
               Regex emailReg = new Regex("^\\s*([A-Za-z0-9_-]+(\\.\\w+)*@(\\w+\\.)+\\w{2,5})\\s*$");
               if (columnName == "UserName" && String.IsNullOrEmpty(this.UserName))
               {
                   return "用戶名不能為空";
               }
               
               if (columnName == "UserPhone" && !String.IsNullOrEmpty(this.UserPhone))
               {
                   if (!digitalReg.IsMatch(this.UserPhone.ToString()))
                   {
                       return "用戶電話必須為8-11位的數(shù)值！";
                   }
               }
               if (columnName == "UserEmail" && !String.IsNullOrEmpty(this.UserEmail))
               {
                   if (!emailReg.IsMatch(this.UserEmail.ToString()))
                   {
                       return "用戶郵箱地址不正確！";
                   }
               }
               return null;
           }
       }
   }

繼承IDataErrorInfo接口后，實(shí)現(xiàn)方法兩個(gè)屬性：Error 屬性用于指示整個(gè)對(duì)象的錯(cuò)誤，而索引器用于指示單個(gè)屬性級(jí)別的錯(cuò)誤。

每次的屬性值發(fā)生變化，則索引器進(jìn)行一次檢查，看是否有驗(yàn)證錯(cuò)誤的信息返回。

兩者的工作原理相同：如果返回非 null 或非空字符串，則表示存在驗(yàn)證錯(cuò)誤。否則，返回的字符串用于向用戶顯示錯(cuò)誤。 

結(jié)果如圖：

 利用 IDataErrorInfo 的好處是它可用于輕松地處理交叉耦合屬性。但也具有一個(gè)很大的弊端：
索引器的實(shí)現(xiàn)通常會(huì)導(dǎo)致較大的 switch-case 語句（對(duì)象中的每個(gè)屬性名稱都對(duì)應(yīng)于一種情況），
必須基于字符串進(jìn)行切換和匹配，并返回指示錯(cuò)誤的字符串。而且，在對(duì)象上設(shè)置屬性值之前，不會(huì)調(diào)用 IDataErrorInfo 的實(shí)現(xiàn)。

為了避免出現(xiàn)大量的 switch-case，并且將校驗(yàn)邏輯進(jìn)行分離提高代碼復(fù)用，將驗(yàn)證規(guī)則和驗(yàn)證信息獨(dú)立化于于每個(gè)模型對(duì)象中， 使用DataAnnotations 無疑是最好的的方案 。

所以我們進(jìn)行改良一下：

View代碼，跟上面那個(gè)一樣：

<GroupBox Header="IDataErrorInfo+ 驗(yàn)證" Margin="10 20 10 10" DataContext="{Binding Source={StaticResource Locator},Path=BindDataAnnotations}" >
         <StackPanel Orientation="Vertical" Margin="0,20,0,0">
             <StackPanel>
                 <Label Content="用戶名" Target="{Binding ElementName=UserName}"/>
                 <TextBox Width="150" 
                      Text="{Binding UserName,UpdateSourceTrigger=PropertyChanged,ValidatesOnDataErrors=True}" >
                 </TextBox>
             </StackPanel>
             <StackPanel>
                 <Label Content="性別" Target="{Binding ElementName=RadioGendeMale}"/>
                 <RadioButton Content="男" />
                 <RadioButton Content="女" Margin="8,0,0,0" />
             </StackPanel>
             <StackPanel>
                 <Label Content="生日" Target="{Binding ElementName=DateBirth}" />
                 <DatePicker />
             </StackPanel>
             <StackPanel>
                 <Label Content="用戶郵箱" Target="{Binding ElementName=UserEmail}"/>
                 <TextBox Width="150" Text="{Binding UserEmail, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" />
             </StackPanel>
             <StackPanel>
                 <Label Content="用戶電話" Target="{Binding ElementName=UserPhone}"/>
                 <TextBox Width="150" Text="{Binding UserPhone,UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" />
             </StackPanel>
             <Button Content="提交" Margin="100,16,0,0" HorizontalAlignment="Left" Command="{Binding ValidFormCommand}" />
         </StackPanel>

</GroupBox>

 VideModel代碼：

using GalaSoft.MvvmLight;
using System;
using System.Collections.Generic;
using System.Linq;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using GalaSoft.MvvmLight.Command;
using System.Windows;

namespace MVVMLightDemo.ViewModel
{
    [MetadataType(typeof(BindDataAnnotationsViewModel))]
    public class BindDataAnnotationsViewModel : ViewModelBase, IDataErrorInfo
    {
        public BindDataAnnotationsViewModel()
        {    
        }
        #region 屬性 
        /// <summary>
        /// 表單驗(yàn)證錯(cuò)誤集合
        /// </summary>
        private Dictionary<String, String> dataErrors = new Dictionary<String, String>();
        private String userName;
        /// <summary>
        /// 用戶名
        /// </summary>
        [Required]
        public String UserName
        {
            get { return userName; }
            set { userName = value; }
        }
        private String userPhone;
        /// <summary>
        /// 用戶電話
        /// </summary>
        [Required]
        [RegularExpression(@"^[-]?[1-9]{8,11}\d*$|^[0]{1}$", ErrorMessage = "用戶電話必須為8-11位的數(shù)值.")]
        public String UserPhone
        {
            get { return userPhone; }
            set { userPhone = value; }
        }
        private String userEmail;
        /// <summary>
        /// 用戶郵件
        /// </summary>
        [Required]
        [StringLength(100,MinimumLength=2)]
        [RegularExpression("^\\s*([A-Za-z0-9_-]+(\\.\\w+)*@(\\w+\\.)+\\w{2,5})\\s*$", ErrorMessage = "請(qǐng)?zhí)顚懻_的郵箱地址.")]
        public String UserEmail
        {
            get { return userEmail; }
            set { userEmail = value; }
        }
        #endregion
        #region 命令
        private RelayCommand validFormCommand;
        /// <summary>
        /// 驗(yàn)證表單
        /// </summary>
        public RelayCommand ValidFormCommand
        {
            get
            {
                if (validFormCommand == null)
                    return new RelayCommand(() => ExcuteValidForm());
                return validFormCommand;
            }
            set { validFormCommand = value; }
        }
        /// <summary>
        /// 驗(yàn)證表單
        /// </summary>
        private void ExcuteValidForm()
        {
            if (dataErrors.Count == 0) MessageBox.Show("驗(yàn)證通過！");
            else MessageBox.Show("驗(yàn)證失?。?quot;);
        }
        #endregion
        public string this[string columnName]
        {
            get
            {
                ValidationContext vc = new ValidationContext(this, null, null);
                vc.MemberName = columnName;
                var res = new List<ValidationResult>();
                var result = Validator.TryValidateProperty(this.GetType().GetProperty(columnName).GetValue(this, null), vc, res);
                if (res.Count > 0)
                {
                    AddDic(dataErrors,vc.MemberName);
                    return string.Join(Environment.NewLine, res.Select(r => r.ErrorMessage).ToArray());
                }
                RemoveDic(dataErrors,vc.MemberName);
                return null;
            }
        }
        public string Error
        {
            get
            {
                return null;
            }
        }
        #region 附屬方法
        /// <summary>
        /// 移除字典
        /// </summary>
        /// <param name="dics"></param>
        /// <param name="dicKey"></param>
        private void RemoveDic(Dictionary<String, String> dics, String dicKey)
        {
            dics.Remove(dicKey);
        }
        /// <summary>
        /// 添加字典
        /// </summary>
        /// <param name="dics"></param>
        /// <param name="dicKey"></param>
        private void AddDic(Dictionary<String, String> dics, String dicKey)
        {
            if (!dics.ContainsKey(dicKey)) dics.Add(dicKey, "");
        }
        #endregion
    }
}

  DataAnnotations相信很多人很熟悉，可以使用數(shù)據(jù)批注來自定義用戶的模型數(shù)據(jù)，記得引用 System.ComponentModel.DataAnnotations。

他包含如下幾個(gè)驗(yàn)證類型： 

    這邊我們使用到了RequiredAttribute、StringLengthAttribute、RegularExpressionAttribute 三項(xiàng)，如果有需要進(jìn)一步了解 DataAnnotations 的可以參考微軟官網(wǎng)：

https://msdn.microsoft.com/en-us/library/dd901590(VS.95).aspx

用 DataAnnotions 后，Model 的更加簡潔，校驗(yàn)也更加靈活?？梢辕B加組合驗(yàn)證 , 面對(duì)復(fù)雜驗(yàn)證模式的時(shí)候，可以自由的使用正則來驗(yàn)證。

默認(rèn)情況下，框架會(huì)提供相應(yīng)需要反饋的消息內(nèi)容，當(dāng)然也可以自定義錯(cuò)誤消息內(nèi)容：ErrorMessage 。

這邊我們還加了個(gè)全局的錯(cuò)誤集合收集器 ：dataErrors，在提交判斷時(shí)候判斷是否驗(yàn)證通過。

這邊我們進(jìn)一步封裝索引器，并且通過反射技術(shù)讀取當(dāng)前字段下的屬性進(jìn)行驗(yàn)證。

 結(jié)果如下：

封裝ValidateModelBase類：

上面的驗(yàn)證比較合理了，不過相對(duì)于開發(fā)人員還是太累贅了，開發(fā)人員關(guān)心的是Model的DataAnnotations的配置，而不是關(guān)心在這個(gè)ViewModel要如何做驗(yàn)證處理，所以我們進(jìn)一步抽象。

編寫一個(gè)ValidateModelBase，把需要處理的工作都放在里面。需要驗(yàn)證屬性的Model去繼承這個(gè)基類。如下：

ValidateModelBase 類，請(qǐng)注意標(biāo)紅部分：

 public class ValidateModelBase : ObservableObject, IDataErrorInfo
     {
         public ValidateModelBase()
         {
               
         }
         #region 屬性 
         /// <summary>
         /// 表當(dāng)驗(yàn)證錯(cuò)誤集合
         /// </summary>
         private Dictionary<String, String> dataErrors = new Dictionary<String, String>();
 
         /// <summary>
         /// 是否驗(yàn)證通過
         /// </summary>
         public Boolean IsValidated
         {
             get
             {
                 if (dataErrors != null && dataErrors.Count > 0)
                 {
                     return false;
                 }
                 return true;
             }
         }
         #endregion
         public string this[string columnName]
         {
             get
             {
                 ValidationContext vc = new ValidationContext(this, null, null);
                 vc.MemberName = columnName;
                 var res = new List<ValidationResult>();
                 var result = Validator.TryValidateProperty(this.GetType().GetProperty(columnName).GetValue(this, null), vc, res);
                 if (res.Count > 0)
                 {
                     AddDic(dataErrors, vc.MemberName);
                     return string.Join(Environment.NewLine, res.Select(r => r.ErrorMessage).ToArray());
                 }
                 RemoveDic(dataErrors, vc.MemberName);
                 return null;
             }
         }
         public string Error
         {
             get
             {
                 return null;
             }
         }
         #region 附屬方法
         /// <summary>
         /// 移除字典
         /// </summary>
         /// <param name="dics"></param>
         /// <param name="dicKey"></param>
         private void RemoveDic(Dictionary<String, String> dics, String dicKey)
         {
             dics.Remove(dicKey);
         }
         /// <summary>
         /// 添加字典
         /// </summary>
         /// <param name="dics"></param>
         /// <param name="dicKey"></param>
         private void AddDic(Dictionary<String, String> dics, String dicKey)
         {
             if (!dics.ContainsKey(dicKey)) dics.Add(dicKey, "");
         }
         #endregion
     }

 驗(yàn)證的模型類：繼承 ValidateModelBase

[MetadataType(typeof(BindDataAnnotationsViewModel))]
    public class ValidateUserInfo : ValidateModelBase
    {
        #region 屬性 
        private String userName;
        /// <summary>
        /// 用戶名
        /// </summary>
        [Required]
        public String UserName
        {
            get { return userName; }
            set { userName = value; RaisePropertyChanged(() => UserName); }
        }
        private String userPhone;
        /// <summary>
        /// 用戶電話
        /// </summary>
        [Required]
        [RegularExpression(@"^[-]?[1-9]{8,11}\d*$|^[0]{1}$", ErrorMessage = "用戶電話必須為8-11位的數(shù)值.")]
        public String UserPhone
        {
            get { return userPhone; }
            set { userPhone = value; RaisePropertyChanged(() => UserPhone); }
        }
        private String userEmail;
        /// <summary>
        /// 用戶郵件
        /// </summary>
        [Required]
        [StringLength(100, MinimumLength = 2)]
        [RegularExpression("^\\s*([A-Za-z0-9_-]+(\\.\\w+)*@(\\w+\\.)+\\w{2,5})\\s*$", ErrorMessage = "請(qǐng)?zhí)顚懻_的郵箱地址.")]
        public String UserEmail
        {
            get { return userEmail; }
            set { userEmail = value; RaisePropertyChanged(() => UserEmail);  }
        }
        #endregion
    }

  ViewModel代碼如下：

public class PackagedValidateViewModel:ViewModelBase
   {
       public PackagedValidateViewModel()
       {
           ValidateUI = new Model.ValidateUserInfo();
       }

       #region 全局屬性
       private ValidateUserInfo validateUI;
       /// <summary>
       /// 用戶信息
       /// </summary>
       public ValidateUserInfo ValidateUI
       {
           get
           {
               return validateUI;
           }

           set
           {
               validateUI = value;
               RaisePropertyChanged(()=>ValidateUI);
           }
       }             
       #endregion
       #region 全局命令
       private RelayCommand submitCmd;
       public RelayCommand SubmitCmd
       {
           get
           {
               if(submitCmd == null) return new RelayCommand(() => ExcuteValidForm());
               return submitCmd;
           }

           set
           {
               submitCmd = value;
           }
       }
       #endregion
       #region 附屬方法
       /// <summary>
       /// 驗(yàn)證表單
       /// </summary>
       private void ExcuteValidForm()
       {
           if (ValidateUI.IsValidated) MessageBox.Show("驗(yàn)證通過！");
           else MessageBox.Show("驗(yàn)證失敗！");
       }
       #endregion
   }

 結(jié)果如下：

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