c# – 使用数据注释的WPF MVVM验证
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我是wpf mvvm架构的新手.插件更新正在使用linq到sql.I需要使用数据注释进行验证.我们如何使用数据注释提供验证.任何人都可以给出一些好的例子吗？
我的模型是
namespace EmployeeApp.Model
{
public class Employee : ObservableObject
{
#region Constructor
public Employee(int empId = 0, string empName = "", int age = 0)
{
_empId = empId;
_empName = empName;
_age = age;
}
#endregion
#region Properties
private int _empId = 0;
public int EmpId
{
get { return _empId; }
set
{
_empId = value;
RaisePropertyChangedEvent("ID");
}
}
private string _empName = string.Empty;
public string EmpName
{
get { return _empName; }
set
{
_empName = value;
RaisePropertyChangedEvent("Name");
}
}
private int _age = 0;
public int Age
{
get { retuenter code heren _age; }
set
{
_age = value;
RaisePropertyChangedEvent("Age");
}
}
#endregion
}
}
提前致谢.
解决方法:
例如：Code MSDN Reference Data Annotations
在模型类中添加引用：
using System.ComponentModel.DataAnnotations;
然后只需以下属性.
[Required(ErrorMessage = "Email address is required")]
[EmailAddress(ErrorMessage = "Email Address is Invalid")]
public string Email
{
get { return GetValue(() => Email); }
set { SetValue(() => Email, value); }
}
更新完整示例：
您的类应使用基类PropertyChangedNotification
创建clas PropertyChangedNotification,如下所示(在链接的页面中,您可以找到它)
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;
namespace EmployeeApp.Notification
{
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
}
}
在您的视图中,您可以添加：
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<TextBox Grid.Column="0"
Name="txtEmail"
Text="{Binding Email, Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged,
ValidatesOnDataErrors=True, NotifyOnValidationError=True}" Width="100">
</TextBox>
<TextBlock Grid.Column="1" Grid.Row="0"
Text="{Binding (Validation.Errors)[0].ErrorContent, ElementName=txtEmail}"
Foreground="Red" Margin="5,0,0,0"/>
</Grid>
关于按钮单击的验证,只需执行命令并在那里引发通知.
点击验证的更改
视图
<TextBox Grid.Column="0"
Name="txtTestValue" Text="{Binding MyTextValue, Mode=TwoWay, ValidatesOnDataErrors=True, NotifyOnValidationError=True}" Width="100">
</TextBox>
<TextBlock Grid.Column="1" Grid.Row="0" Text="{Binding (Validation.Errors)[0].ErrorContent, ElementName=txtTestValue}" Foreground="Red" Margin="5,0,0,0"/>
<Button Content="Validate" Command="{Binding ValidationCommand}">
</Button>
模型
ValidationCommand = new RelayCommand(ExecuteMyCommand,() => true);
….
public RelayCommand ValidationCommand
{
get;
private set;
}
private void ExecuteMyCommand()
{
OnValidate("MyTextValue");
}
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