DataAnnotations方法定义WPF输入异常祥解

在MVVM中，我们一般将前台xaml需绑定的变量统一写在ViewModel中，而对于数据的验证，也会在viewModel中进行处理：

这里详解DataAnnotations方法：

首先ViewModel需要引用System.ComponentModel.DataAnnotations，接下来我们需要为viewModel建立viewModelBase类，方便所有viewModel统一处理验证，

base类中可写的东西有很多，这边列出2个我们需要的方法:

    public class ViewModelBase : IDataErrorInfo    {        public string this[string columnName]        {            get            {                var validationResults = new List<ValidationResult>();                if (Validator.TryValidateProperty(GetType().GetProperty(columnName).GetValue(this, null),                                                  new ValidationContext(this, null, null) { MemberName = columnName },                                                  validationResults))                {                    return null;                }                return validationResults.First().ErrorMessage;            }        }        protected bool IsValid()        {            return Validator.TryValidateObject(                this, new ValidationContext(this, null, null), new List<ValidationResult>(), true);        }    }

这样以后，我们就能在viewModel中进行相关验证了“：

    public class SampleViewModel : ViewModelBase    {        public int ID { get; set; }        [Display(Name = "Condition Name")]        [Required(ErrorMessageResourceName = ValidationErrorMessagesResourceNames.Required,            ErrorMessageResourceType = typeof(ValidationErrorMessages))]        [StringLength(30, ErrorMessageResourceName = ValidationErrorMessagesResourceNames.StringMaximumLength,            ErrorMessageResourceType = typeof(ValidationErrorMessages))]        public string Name { get; set; }    }

提示的message可以自定义resource，而DataAnnotations

 [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter,        AllowMultiple = false)]    public class StringValidate : ValidationAttribute    {         private static readonly Regex InvalidRegex              = new Regex(@"[^a-zA-Z0-9 -/:-@\[-\`\{-\~]");        public StringValidate()            : base(() => "Error string")        {        }         public override bool IsValid(object value)         {             var s = Convert.ToString(value);             if (string.IsNullOrEmpty(s)) return true;             return !InvalidRegex.IsMatch(s);         }    }

最后我们的viewModel就能变成：

 public class SampleViewModel : ViewModelBase    {        public int ID { get; set; }        [Display(Name = "Condition Name")]        [Required(ErrorMessageResourceName = ValidationErrorMessagesResourceNames.Required,            ErrorMessageResourceType = typeof(ValidationErrorMessages))]        [StringLength(30, ErrorMessageResourceName = ValidationErrorMessagesResourceNames.StringMaximumLength,            ErrorMessageResourceType = typeof(ValidationErrorMessages))]        [StringValidate]        public string Name { get; set; }    }

即Name只限输入英语，数字，符号，别的全角字符一律不行。

最后，在xmal中定义以下style：

    <Style x:Key="TextBoxStyleBase" TargetType="TextBox">        <Style.Triggers>            <!-- Validation エラー時にエラー内容を ToolTip 表示する -->            <Trigger Property="Validation.HasError" Value="True">                <Setter Property="ToolTip"                        Value="{Binding (Validation.Errors)[0].ErrorContent, RelativeSource={RelativeSource Mode=Self}}" />            </Trigger>        </Style.Triggers>    </Style>

这里提示是用tooltip提示，当然还可以用adornedElementPlaceHolder这种旁边的修饰框

  <Style x:Key="ValidateTextBoxStyle" TargetType="TextBox">                        <Style.Triggers>                        <Trigger Property="Validation.HasError" Value="true">                            <Setter Property="Validation.ErrorTemplate">                                <Setter.Value>                                    <ControlTemplate>                                        <DockPanel LastChildFill="True">                                            <TextBlock DockPanel.Dock="Left" Background="Red" Foreground="White" FontSize="11" Height="17"                                                       Width="Auto"                                                       VerticalAlignment="Center" TextAlignment="Center" TextWrapping="Wrap" FontFamily="Arial"                                                  Text="{Binding ElementName=ErrorBox, Path=AdornedElement.(Validation.Errors)[0].ErrorContent}">                                            </TextBlock>                                            <AdornedElementPlaceholder Name="ErrorBox" />                                        </DockPanel>                                    </ControlTemplate>                                </Setter.Value>                            </Setter>                        </Trigger>                    </Style.Triggers>                    </Style>

 

最后在binding的时候设置ValidatesOnDataErrors=true就可以了