using Prism.Mvvm;
using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Runtime.CompilerServices;
namespace TreasurerHelper.Infrastructure.Models
{
/// <summary>
/// Base domain object class.
/// </summary>
/// <remarks>
/// Provides support for implementing <see cref="INotifyPropertyChanged"/> and
/// implements <see cref="INotifyDataErrorInfo"/> using <see cref="ValidationAttribute"/> instances
/// on the validated properties.
/// </remarks>
public abstract class DomainObject : INotifyPropertyChanged, INotifyDataErrorInfo
{
private ErrorsContainer<ValidationResult> errorsContainer;
/// <summary>
/// Initializes a new instance of the <see cref="DomainObject"/> class.
/// </summary>
protected DomainObject()
{
}
/// <summary>
/// sets the storage to the value
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="storage"></param>
/// <param name="value"></param>
/// <param name="propertyName"></param>
/// <returns>True if the value was changed, false if the existing value matched the desired value.</returns>
protected bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
{
ValidateProperty(propertyName, value);
if (object.Equals(storage, value)) return false;
storage = value;
OnPropertyChanged(propertyName);
return true;
}
/// <summary>
/// Notifies listeners that a property value has changed.
/// </summary>
/// <param name="propertyName">Name of the property used to notify listeners. This
/// value is optional and can be provided automatically when invoked from compilers
/// that support <see cref="CallerMemberNameAttribute"/>.</param>
protected void OnPropertyChanged(string propertyName)
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
/// <summary>
/// Event raised when a property value changes.
/// </summary>
/// <seealso cref="INotifyPropertyChanged"/>
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Event raised when the validation status changes.
/// </summary>
/// <seealso cref="INotifyDataErrorInfo"/>
public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;
/// <summary>
/// Gets the error status.
/// </summary>
/// <seealso cref="INotifyDataErrorInfo"/>
public bool HasErrors
{
get { return this.ErrorsContainer.HasErrors; }
}
/// <summary>
/// Gets the container for errors in the properties of the domain object.
/// </summary>
protected ErrorsContainer<ValidationResult> ErrorsContainer
{
get
{
if (this.errorsContainer == null)
{
this.errorsContainer =
new ErrorsContainer<ValidationResult>(pn => this.RaiseErrorsChanged(pn));
}
return this.errorsContainer;
}
}
/// <summary>
/// Returns the errors for <paramref name="propertyName"/>.
/// </summary>
/// <param name="propertyName">The name of the property for which the errors are requested.</param>
/// <returns>An enumerable with the errors.</returns>
/// <seealso cref="INotifyDataErrorInfo"/>
public IEnumerable GetErrors(string propertyName)
{
return this.errorsContainer.GetErrors(propertyName);
}
/// <summary>
/// Raises the <see cref="PropertyChanged"/> event.
/// </summary>
/// <param name="propertyName">The name of the changed property.</param>
protected void RaisePropertyChanged(string propertyName)
{
this.OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
/// <summary>
/// Raises the <see cref="PropertyChanged"/> event.
/// </summary>
/// <param name="e">The argument for the event.</param>
protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
{
this.PropertyChanged?.Invoke(this, e);
}
/// <summary>
/// Validates <paramref name="value"/> as the value for the property named <paramref name="propertyName"/>.
/// </summary>
/// <param name="propertyName">The name of the property.</param>
/// <param name="value">The value for the property.</param>
protected void ValidateProperty(string propertyName, object value)
{
if (string.IsNullOrEmpty(propertyName))
{
throw new ArgumentNullException("propertyName");
}
this.ValidateProperty(new ValidationContext(this, null, null) { MemberName = propertyName }, value);
}
/// <summary>
/// Validates <paramref name="value"/> as the value for the property specified by
/// <paramref name="validationContext"/> using data annotations validation attributes.
/// </summary>
/// <param name="validationContext">The context for the validation.</param>
/// <param name="value">The value for the property.</param>
protected virtual void ValidateProperty(ValidationContext validationContext, object value)
{
if (validationContext == null)
{
throw new ArgumentNullException("validationContext");
}
List<ValidationResult> validationResults = new List<ValidationResult>();
Validator.TryValidateProperty(value, validationContext, validationResults);
this.ErrorsContainer.SetErrors(validationContext.MemberName, validationResults);
}
/// <summary>
/// Raises the <see cref="ErrorsChanged"/> event.
/// </summary>
/// <param name="propertyName">The name of the property which changed its error status.</param>
protected void RaiseErrorsChanged(string propertyName)
{
this.OnErrorsChanged(new DataErrorsChangedEventArgs(propertyName));
}
/// <summary>
/// Raises the <see cref="ErrorsChanged"/> event.
/// </summary>
/// <param name="e">The argument for the event.</param>
protected virtual void OnErrorsChanged(DataErrorsChangedEventArgs e)
{
this.ErrorsChanged?.Invoke(this, e);
}
}
}
