[Silverlight入门系列]使用MVVM模式(5)：异步Validation数据验证和INotifyDataErrorInfo接口

数据验证（Validation）是界面程序的常见需求，例如使用正则表达式验证用户输入的Email地址是否合法，然后在界面给出错误提示信息。在Sivlerlight的MVVM模式中，我们在Model和ViewModel可以做Validation，然后需要把Model和ViewModel的Validation结果和错误信息通知视图（View）。在WPF中，我们使用IDataErrorInfo，在Silverlight4中，建议使用INotifyDataErrorInfo。关于这个接口怎么使用，如何实现ErrorProvider的功能，如何做DataForm的Validatio，请参考我的旧一篇。

IDataErrorInfo

先简单说一下IDataErrorInfo，这个接口实现了简单的数据验证和错误报告功能，只能说聊胜于无吧。例子：

<TextBox Text="{Binding Path=CurrentEmployee.Name, Mode=TwoWay, ValidatesOnDataErrors=True, NotifyOnValidationError=True }" />

INotifyDataErrorInfo

这个接口只有Silverlight4以上支持，非常强大，支持一个绑定属性多重错误、异步数据验证、自动通知视图错误信息、ErrorChanged事件、HasErrors属性、GetErrors方法等等。定义：

public interface INotifyDataErrorInfo
2 {
3      bool HasErrors { get; }
4 
5      event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;
6 
7      IEnumerable GetErrors(string propertyName);
8 }

实现这个INotifyDataErrorInfo接口也非常简单，来个简单的例子：

public class SimpleModel : INotifyDataErrorInfo
 2 {
 3     public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;
 4 
 5     private Dictionary<string, List<String>> _errors = new Dictionary<string, List<String>>();
 6 
 7     private string _accountID = null;
 8 
 9     public string AccountID
10     {
11         get { return _accountID; }
12         set
13         {
14             if (_accountID != value)
15             {
16                 var propertyName = "AccountID";
17 
18                 if (string.IsNullOrEmpty(value))
19                 {
20                     if (!_errors.ContainsKey(propertyName))
21                         _errors.Add(propertyName, new List<string>());
22 
23                     _errors[propertyName].Add("AccountID can't be null or empty");
24                 }
25                 else
26                 {
27                     if (_errors.ContainsKey(propertyName))
28                        _errors.Remove(propertyName);
29                 }
30 
31                 NotifyErrorsChanged(propertyName);
32 
33                 //Maybe you don't want to set this field to a value if the validation fails
34                  _accountID = value;
35             }
36         }
37 
38     }
39 
40     public System.Collections.IEnumerable GetErrors(string propertyName)
41     {
42         if (_errors.ContainsKey(propertyName))
43             return _errors[propertyName];
44 
45         return _errors.Values;
46     }
47 
48     public bool HasErrors
49     {
50         get { return _errors.Count > 0; }
51     }
52 
53 
54     private void NotifyErrorsChanged(string propertyName)
55     {
56         if (ErrorsChanged != null)
57             ErrorsChanged(this, new DataErrorsChangedEventArgs(propertyName));
58     }
59 }

异步Validation数据验证和INotifyDataErrorInfo接口

这个例子稍微复杂，实现了异步调用WCF RIA Service进行业务逻辑的validation并在ViewModel中把验证的错误提示通知视图，完整的代码下载，需要VS2010和Silverlight环境。

代码说明 ViewModel基类：

using System;
  2 using System.Net;
  3 using System.Windows;
  4 using System.Linq;
  5 using System.Windows.Controls;
  6 using System.Windows.Documents;
  7 using System.Windows.Ink;
  8 using System.Windows.Input;
  9 using System.Windows.Media;
 10 using System.Windows.Media.Animation;
 11 using System.Windows.Shapes;
 12 using System.ComponentModel;
 13 using System.Collections.Generic;
 14 using System.Collections;
 15 
 16 namespace AsycValidation
 17 {
 18     public class BasicViewModel : INotifyPropertyChanged, INotifyDataErrorInfo
 19     {
 20         public event PropertyChangedEventHandler PropertyChanged;
 21         public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;
 22 
 23 
 24         private Dictionary<string, List<ValidationErrorInfo>> _errors =
 25                       new Dictionary<string, List<ValidationErrorInfo>>();
 26 
 27 
 28         protected void RemoveErrorFromPropertyAndNotifyErrorChanges(
 29                                  string propertyName,
 30                                  int errorCode)
 31         {
 32             if (_errors.ContainsKey(propertyName))
 33             {
 34                 RemoveErrorFromPropertyIfErrorCodeAlreadyExist(propertyName, errorCode);
 35 
 36                 NotifyErrorsChanged(propertyName);
 37             }
 38         }
 39 
 40         private void RemoveErrorFromPropertyIfErrorCodeAlreadyExist(
 41                                  string propertyName,
 42                                  int errorCode)
 43         {
 44             if (_errors.ContainsKey(propertyName))
 45             {
 46                 var errorToRemove = _errors[propertyName].SingleOrDefault(
 47                                        error => error.ErrorCode == errorCode);
 48 
 49                 if (errorToRemove != null)
 50                 {
 51                     _errors[propertyName].Remove(errorToRemove);
 52 
 53 
 54 
 55 
 56                     if (_errors[propertyName].Count == 0)
 57                         _errors.Remove(propertyName);
 58                 }
 59             }
 60         }
 61         protected void AddErrorToPropertyAndNotifyErrorChanges(
 62                                   string propertyName,
 63                                   ValidationErrorInfo errorInfo)
 64         {
 65             RemoveErrorFromPropertyIfErrorCodeAlreadyExist(propertyName, errorInfo.ErrorCode);
 66             if (!_errors.ContainsKey(propertyName))
 67                 _errors.Add(propertyName, new List<ValidationErrorInfo>());
 68 
 69             _errors[propertyName].Add(errorInfo);
 70 
 71             NotifyErrorsChanged(propertyName);
 72         }
 73 
 74 
 75         public IEnumerable GetErrors(string propertyName)
 76         {
 77             if (!_errors.ContainsKey(propertyName))
 78                 return _errors.Values;
 79 
 80             return _errors[propertyName];
 81         }
 82 
 83 
 84         public bool HasErrors
 85         {
 86             get { return this._errors.Count > 0; }
 87         }
 88 
 89 
 90         private void NotifyErrorsChanged(string propertyName)
 91         {
 92             if (ErrorsChanged != null)
 93                 ErrorsChanged(this, new DataErrorsChangedEventArgs(propertyName));
 94         }
 95 
 96 
 97         protected void NotifyPropertyChanged(string propertyName)
 98         {
 99             if (PropertyChanged != null)
100                 PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
101         }
102 
103     }
104 }

Model:

using System;
 2 using System.Net;
 3 using System.Windows;
 4 using System.Windows.Controls;
 5 using System.Windows.Documents;
 6 using System.Windows.Ink;
 7 using System.Windows.Input;
 8 using System.Windows.Media;
 9 using System.Windows.Media.Animation;
10 using System.Windows.Shapes;
11 using System.ComponentModel;
12 
13 namespace AsycValidation
14 {
15     public class CompanyModel : INotifyPropertyChanged
16     {
17         public event PropertyChangedEventHandler PropertyChanged;
18 
19         public int CompanyID { get; set; }
20 
21         private string _CompanyName;
22         public string CompanyName
23         {
24             get { return _CompanyName; }
25             set
26             {
27                 _CompanyName = value;
28 
29                 if (PropertyChanged != null)
30                 {
31                     PropertyChanged(this, new PropertyChangedEventArgs("CompanyName"));
32                 }
33             }
34         }
35     }
36 }

ViewModel，继承了BaseViewModel基类:

using System;
 2 using System.Net;
 3 using System.Windows;
 4 using System.Windows.Controls;
 5 using System.Windows.Documents;
 6 using System.Windows.Ink;
 7 using System.Windows.Input;
 8 using System.Windows.Media;
 9 using System.Windows.Media.Animation;
10 using System.Windows.Shapes;
11 using AsycValidation.Web;
12 
13 namespace AsycValidation
14 {
15     public class CompanyViewModel : BasicViewModel
16     {
17         public CompanyModel CompanyModelData { get; set; }
18 
19         public CompanyViewModel(CompanyModel model)
20         {
21             CompanyModelData = model;
22         }
23 
24         private string _CompanyName = null;
25         private const int ACCOUNT_ALREADY_EXIST_ERROCODE = 100;
26 
27         DomainService1 service = new DomainService1();
28 
29         public string CompanyName
30         {
31             get
32             {
33                 return _CompanyName;
34             }
35             set
36             {
37                 if (_CompanyName != value)
38                 {
39                     var propertyName = "CompanyName";
40 
41                     ValidateAccountAlreadyExists(
42                                     value,
43                                     propertyName,
44                                     ACCOUNT_ALREADY_EXIST_ERROCODE,
45                                     string.Format("Company with the ID {0} already exists", value));
46 
47                     _CompanyName = value;
48                     NotifyPropertyChanged(propertyName);
49                 }
50             }
51         }
52 
53         private void ValidateAccountAlreadyExists(
54                                         string CompanyID,
55                                         string propertyName,
56                                         int errorCode,
57                                         string errorMsg)
58         {
59             service.DoesCompanyExists(
60                  CompanyID,
61                  invokeOperation =>
62                  {
63                      if (invokeOperation.Value)
64                      {
65                          AddErrorToPropertyAndNotifyErrorChanges(
66                              propertyName,
67                              new ValidationErrorInfo()
68                              {
69                                  ErrorCode = errorCode,
70                                  ErrorMessage = errorMsg
71                              });
72                      }
73                      else
74                      {
75                          RemoveErrorFromPropertyAndNotifyErrorChanges(
76                                propertyName,
77                                errorCode);
78                      }
79                  },
80                  null);
81         }
82 
83     }
84 }

View / XAML

<UserControl x:Class="AsycValidation.MainPage"
 2     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 3     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 4     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
 5     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 6     xmlns:wm="clr-namespace:AsycValidation"
 7     mc:Ignorable="d"
 8     d:DesignHeight="300" d:DesignWidth="400">
 9 
10     <Grid Name="Layout" >
11         <TextBlock Height="32" HorizontalAlignment="Left" Margin="41,53,0,0" Name="textBlock1" Text="Company:" VerticalAlignment="Top" Width="66" />
12         <TextBox Height="31" HorizontalAlignment="Left" Margin="120,45,0,0" Name="textBox1" Text="{Binding CompanyName, Mode=TwoWay, NotifyOnValidationError=True}" VerticalAlignment="Top" Width="119" />
13         <TextBox Height="30" HorizontalAlignment="Left" Margin="120,104,0,0" Name="textBox2" VerticalAlignment="Top" Width="119" />
14         <Button Content="Button" Height="36" HorizontalAlignment="Left" Margin="120,156,0,0" Name="button1" VerticalAlignment="Top" Width="81" />
15     </Grid>
16 </UserControl>

XAML.CS

using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Net;
 5 using System.Windows;
 6 using System.Windows.Controls;
 7 using System.Windows.Documents;
 8 using System.Windows.Input;
 9 using System.Windows.Media;
10 using System.Windows.Media.Animation;
11 using System.Windows.Shapes;
12 
13 namespace AsycValidation
14 {
15     public partial class MainPage : UserControl
16     {
17         public MainPage()
18         {
19             InitializeComponent();
20 
21             CompanyModel m1 = new CompanyModel() {  CompanyID = 1, CompanyName = "abc" };
22 
23             companyViewModel = new CompanyViewModel(m1);
24             this.DataContext = companyViewModel;
25         }
26 
27         public CompanyViewModel companyViewModel { get; set; }
28     }
29 }

WCF Ria Service:

namespace AsycValidation.Web
 2 {
 3     using System;
 4     using System.Collections.Generic;
 5     using System.ComponentModel;
 6     using System.ComponentModel.DataAnnotations;
 7     using System.Linq;
 8     using System.ServiceModel.DomainServices.Hosting;
 9     using System.ServiceModel.DomainServices.Server;
10 
11 
12     // TODO: Create methods containing your application logic.
13     [EnableClientAccess()]
14     public class DomainService1 : DomainService
15     {
16         [Invoke]
17         public bool DoesCompanyExists(string companyID)
18         {
19             if (companyID == "12345")
20                 return true;
21 
22             return false;
23         }
24     }
25 }

这个例子稍微复杂，实现了异步调用WCF RIA Service进行业务逻辑的validation并在ViewModel中把验证的错误提示通知视图，完整的代码下载，需要VS2010和Silverlight环境。

主要示例了MVVM的INotifyDataErrorInfo接口和INotifyPropertyChanged接口，异步Validation, WCF Ria Service调用。