1 public class ViewModel : INotifyPropertyChanged, IDataErrorInfo
 2     {
 3         private string _error;
 4 
 5         public int Age { get; set; }
 6 
 7         public string Error
 8         {
 9             get { return _error; }
10             set { _error = value; OnPropertyChanged(); }
11         }
12 
13         public string Name { get; set; }
14 
15         public event PropertyChangedEventHandler PropertyChanged;
16 
17         public void OnPropertyChanged([CallerMemberName] string propertyName = "")
18         {
19             PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
20         }
21 
22         /// <summary>
23         /// 索引器验证属性
24         /// </summary>
25         /// <param name="columnName"></param>
26         /// <returns></returns>
27         public string this[string columnName]
28         {
29             get
30             {
31                 switch (columnName)
32                 {
33                     case nameof(Name):
34                         if (string.IsNullOrWhiteSpace(Name))
35                         {
36                             return "姓名不能为空";
37                         }
38                         else
39                         {
40                             if (Name.Length < 4)
41                             {
42                                 return "姓名长度不能<4";
43                             }
44                             else if (Name.Length > 12)
45                             {
46                                 return "姓名长度不能>12";
47                             }
48                         }
49                         return "";
50 
51                     case nameof(Age):
52                         if (Age < 0)
53                         {
54                             return "年龄不能<0";
55                         }
56                         else if (Age > 120)
57                         {
58                             return "年龄不能>120";
59                         }
60                         return "";
61 
62                     default:
63                         return "";
64                 }
65             }
66         }
67     }

 1 <Grid>
 2         <StackPanel
 3             Width="300"
 4             HorizontalAlignment="Center"
 5             VerticalAlignment="Center"
 6             Orientation="Vertical">
 7             <StackPanel Orientation="Horizontal">
 8                 <TextBlock Text="姓名:" />
 9                 <TextBox
10                     Width="220"
11                     Margin="5"
12                     Text="{Binding Path=Name, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}"
13                     ToolTip="{Binding RelativeSource={RelativeSource Self}, Path=(Validation.Errors)[0].ErrorContent}" />
14             </StackPanel>
15             <StackPanel Orientation="Horizontal">
16                 <TextBlock Text="年龄:" />
17                 <TextBox
18                     Width="220"
19                     Margin="5"
20                     Text="{Binding Path=Age, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged}"
21                     ToolTip="{Binding RelativeSource={RelativeSource Self}, Path=(Validation.Errors)[0].ErrorContent}" />
22             </StackPanel>
23         </StackPanel>
24     </Grid>