我正在使用MVVM模式处理WPF应用程序，其中我使用DataAnnotations进行验证。 所以我在这个article中实现了类似的解决方案。
然后我尝试在我的viewmodel中添加一个属性 - 名为＆＃34; Age＆＃34; - 只接受数字，范围在1到100之间。
[RegularExpression(@"^[0-9]{1,3}$", ErrorMessage = "Please enter a valid number")]
[Range(1, 100, ErrorMessage = "Age should be between 1 to 100")]
/// <summary>
/// Gets or sets the age.
/// </summary>
public int Age
{
get { return GetValue(() => Age); }
set { SetValue(() => Age, value); }
}
在我的WPF窗口中，我得到了一个绑定到Age的文本框：
<TextBox x:Name="tbx_age"
ToolTip="The age"
Text="{Binding Age, NotifyOnSourceUpdated=True, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}">
</TextBox>
当我启动应用程序时，文本框预先分配为零（＆＃34; 0＆＃34;）。 当我用＃34; 1a＆＃34;替换文本框中的零时我收到错误消息＆＃34;值＆＃39; 1a＆＃39;无法转换＆＃34;。 这不是来自我的代码的常规消息，我无法解释它来自何处。 我在正则表达式或其他方面犯了错误吗？
我已将我的testproject上传到GitHub： Repository 我的意思是项目名为＆＃34; Validation_DataAnnotations＆＃34;。
提前致谢！
这是我用于通知和验证的PropertyChangedNotification类：
public abstract class PropertyChangedNotification : INotifyPropertyChanged, IDataErrorInfo
{
#region Fields
private readonly Dictionary<string, object> _values = new Dictionary<string, object>();
#endregion
#region Protected
/// <summary>
/// Sets the value of a property.
/// </summary>
/// <typeparam name="T">The type of the property value.</typeparam>
/// <param name="propertySelector">Expression tree contains the property definition.</param>
/// <param name="value">The property value.</param>
protected void SetValue<T>(Expression<Func<T>> propertySelector, T value)
{
string propertyName = GetPropertyName(propertySelector);
SetValue<T>(propertyName, value);
}
/// <summary>
/// Sets the value of a property.
/// </summary>
/// <typeparam name="T">The type of the property value.</typeparam>
/// <param name="propertyName">The name of the property.</param>
/// <param name="value">The property value.</param>
protected void SetValue<T>(string propertyName, T value)
{
if (string.IsNullOrEmpty(propertyName))
{
throw new ArgumentException("Invalid property name", propertyName);
}
_values[propertyName] = value;
NotifyPropertyChanged(propertyName);
}
/// <summary>
/// Gets the value of a property.
/// </summary>
/// <typeparam name="T">The type of the property value.</typeparam>
/// <param name="propertySelector">Expression tree contains the property definition.</param>
/// <returns>The value of the property or default value if not exist.</returns>
protected T GetValue<T>(Expression<Func<T>> propertySelector)
{
string propertyName = GetPropertyName(propertySelector);
return GetValue<T>(propertyName);
}
/// <summary>
/// Gets the value of a property.
/// </summary>
/// <typeparam name="T">The type of the property value.</typeparam>
/// <param name="propertyName">The name of the property.</param>
/// <returns>The value of the property or default value if not exist.</returns>
protected T GetValue<T>(string propertyName)
{
if (string.IsNullOrEmpty(propertyName))
{
throw new ArgumentException("Invalid property name", propertyName);
}
object value;
if (!_values.TryGetValue(propertyName, out value))
{
value = default(T);
_values.Add(propertyName, value);
}
return (T)value;
}
/// <summary>
/// Validates current instance properties using Data Annotations.
/// </summary>
/// <param name="propertyName">This instance property to validate.</param>
/// <returns>Relevant error string on validation failure or <see cref="System.String.Empty"/> on validation success.</returns>
protected virtual string OnValidate(string propertyName)
{
if (string.IsNullOrEmpty(propertyName))
{
throw new ArgumentException("Invalid property name", propertyName);
}
string error = string.Empty;
var value = GetValue(propertyName);
var results = new List<System.ComponentModel.DataAnnotations.ValidationResult>(1);
var result = Validator.TryValidateProperty(
value,
new ValidationContext(this, null, null)
{
MemberName = propertyName
},
results);
if (!result)
{
var validationResult = results.First();
error = validationResult.ErrorMessage;
}
return error;
}
#endregion
#region Change Notification
/// <summary>
/// Raised when a property on this object has a new value.
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Raises this object's PropertyChanged event.
/// </summary>
/// <param name="propertyName">The property that has a new value.</param>
protected void NotifyPropertyChanged(string propertyName)
{
this.VerifyPropertyName(propertyName);
PropertyChangedEventHandler handler = this.PropertyChanged;
if (handler != null)
{
var e = new PropertyChangedEventArgs(propertyName);
handler(this, e);
}
}
protected void NotifyPropertyChanged<T>(Expression<Func<T>> propertySelector)
{
var propertyChanged = PropertyChanged;
if (propertyChanged != null)
{
string propertyName = GetPropertyName(propertySelector);
propertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion // INotifyPropertyChanged Members
#region Data Validation
string IDataErrorInfo.Error
{
get
{
throw new NotSupportedException("IDataErrorInfo.Error is not supported, use IDataErrorInfo.this[propertyName] instead.");
}
}
string IDataErrorInfo.this[string propertyName]
{
get
{
return OnValidate(propertyName);
}
}
#endregion
#region Privates
private string GetPropertyName(LambdaExpression expression)
{
var memberExpression = expression.Body as MemberExpression;
if (memberExpression == null)
{
throw new InvalidOperationException();
}
return memberExpression.Member.Name;
}
private object GetValue(string propertyName)
{
object value;
if (!_values.TryGetValue(propertyName, out value))
{
var propertyDescriptor = TypeDescriptor.GetProperties(GetType()).Find(propertyName, false);
if (propertyDescriptor == null)
{
throw new ArgumentException("Invalid property name", propertyName);
}
value = propertyDescriptor.GetValue(this);
_values.Add(propertyName, value);
}
return value;
}
#endregion
#region Debugging
/// <summary>
/// Warns the developer if this object does not have
/// a public property with the specified name. This
/// method does not exist in a Release build.
/// </summary>
[Conditional("DEBUG")]
[DebuggerStepThrough]
public void VerifyPropertyName(string propertyName)
{
// Verify that the property name matches a real,
// public, instance property on this object.
if (TypeDescriptor.GetProperties(this)[propertyName] == null)
{
string msg = "Invalid property name: " + propertyName;
if (this.ThrowOnInvalidPropertyName)
throw new Exception(msg);
else
Debug.Fail(msg);
}
}
/// <summary>
/// Returns whether an exception is thrown, or if a Debug.Fail() is used
/// when an invalid property name is passed to the VerifyPropertyName method.
/// The default value is false, but subclasses used by unit tests might
/// override this property's getter to return true.
/// </summary>
protected virtual bool ThrowOnInvalidPropertyName { get; private set; }
#endregion // Debugging Aides
}
答案 0 :(得分：1)
您正在将TextBox.TextProperty绑定到int-Property＆＃39; Age＆＃39;，因此WPF已经需要将字符串转换为整数，以便将值赋给您的属性。
如果您想自己完成所有转换，则可以绑定到字符串-Properties。 或者，您可以在绑定中设置ValidatesOnDataErrors = False，然后将静默忽略非数字值，数值将更改绑定属性。
答案 1 :(得分：1)
由于int属性从不可以设置为int以外的任何值，因此如果设置TextBox的Text属性，则永远不会调用属性设置器到＆＃34; 1a＆＃34;。世界上没有正则表达式或数据注释可以解决这个问题。
如何自定义WPF运行时尝试转换值＆＃34; 1a＆＃34;时出现的错误消息。在设置属性之前int使用ValidationRule：
<TextBox>
<TextBox.Text>
<Binding Path="Age" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<local:StringToIntValidationRule ValidationStep="RawProposedValue"/>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
...
</TextBox>
public class StringToIntValidationRule : ValidationRule
{
public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)
{
int i;
if (int.TryParse(value.ToString(), out i))
return new ValidationResult(true, null);
return new ValidationResult(false, "Please enter a valid integer value.");
}
}
以下博文中提供了完整的示例和更多相关信息：https://blog.magnusmontin.net/2013/08/26/data-validation-in-wpf/
请注意，视图模型不负责验证其Age属性是否设置为int值。这是控件或视图的责任。