wpf 实现接口 IDataErrorInfo 数据验证

  public class BaseModel : BindableBase, IDataErrorInfo
  {

      public Func<object, bool> UniquenessCheck { get; set; }

      public string this[string columnName]
      {
          get
          {              
              PropertyInfo pi = this.GetType().GetProperty(columnName);

              var value = pi.GetValue(this, null);
              if (pi.IsDefined(typeof(Attrite.RequiredAttribute), true))
              {
                  if (value == null || string.IsNullOrEmpty(value.ToString()))
                      return pi.GetCustomAttribute<Attrite.RequiredAttribute>().PropName = "不能为空";
              }
             
              return string.Empty;
          }
      }

      public string Error => null;

  }

public class UserModel : BaseModel
{
    public UserModel() { }

    private string _userName;
    [Required("不能为空")]
    public string UserName
    {
        get { return _userName; }
        set
        {
            SetProperty(ref _userName, value);
        }
    }
}

 public class MainWindowViewModel : BindableBase
 {
     private string _title = "Prism Application";
     public string Title
     {
         get { return _title; }
         set { SetProperty(ref _title, value); }
     }

     private UserModel _user;
     public UserModel User
     {
         get { return _user; }
         set { SetProperty(ref _user, value); }
     }

     public MainWindowViewModel()
     {
         User = new UserModel();
         User.UserName = "";
     }
 }

 <Grid>
     <TextBox x:Name="tb" Text="{Binding User.UserName, Mode=TwoWay, ValidatesOnDataErrors=True}" />
     <TextBox Text="{Binding Path=(Validation.Errors)[0].ErrorContent, ElementName=tb}" />
 </Grid>