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using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Controls;
using Tango.Core;
using Tango.Core.DI;
namespace Tango.SharedUI
{
/// <summary>
/// Represents an abstract view model.
/// </summary>
/// <seealso cref="Tango.Core.ExtendedObject" />
/// <seealso cref="System.ComponentModel.INotifyDataErrorInfo" />
public abstract class ViewModel : ExtendedObject, INotifyDataErrorInfo
{
private List<KeyValuePair<String, String>> _currentErrors = new List<KeyValuePair<string, string>>(); //Holds the current validation errors.
private bool _hasErrors;
/// <summary>
/// Gets a value that indicates whether the entity has validation errors.
/// </summary>
public bool HasErrors
{
get { return _hasErrors; }
set { _hasErrors = value; RaisePropertyChangedAuto(); }
}
private bool _isBusy;
/// <summary>
/// Gets or sets a value indicating whether this view model is currently busy doing operations.
/// </summary>
public bool IsBusy
{
get { return _isBusy; }
set { _isBusy = value; RaisePropertyChangedAuto(); RaisePropertyChanged(nameof(IsFree)); InvalidateRelayCommands(); }
}
/// <summary>
/// Gets or sets a value indicating whether this view model is free to perform actions.
/// </summary>
public bool IsFree
{
get { return !IsBusy; }
set { IsBusy = !value; }
}
private ObservableCollection<String> _validationErrors;
/// <summary>
/// Gets or sets the validation errors.
/// </summary>
public ObservableCollection<String> ValidationErrors
{
get { return _validationErrors; }
protected set { _validationErrors = value; RaisePropertyChangedAuto(); }
}
/// <summary>
/// Occurs when the validation errors have changed for a property or for the entire entity.
/// </summary>
public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;
/// <summary>
/// Initializes a new instance of the <see cref="ViewModel"/> class.
/// </summary>
public ViewModel()
{
IsFree = true;
}
/// <summary>
/// Gets the validation errors for a specified property or for the entire entity.
/// </summary>
/// <param name="propertyName">The name of the property to retrieve validation errors for; or null or <see cref="F:System.String.Empty" />, to retrieve entity-level errors.</param>
/// <returns>
/// The validation errors for the property or entity.
/// </returns>
public virtual IEnumerable GetErrors(string propertyName)
{
return _currentErrors.Where(x => x.Key == propertyName).Select(x => x.Value).ToList();
}
/// <summary>
/// Invoked the <see cref="ErrorsChanged"/> event.
/// </summary>
/// <param name="propName">Name of the property.</param>
protected void RaiseError(String propName)
{
ErrorsChanged?.Invoke(this, new DataErrorsChangedEventArgs(propName));
}
/// <summary>
/// Validates this view model by <see cref="ValidationAttribute">validation attributes</see>.
/// </summary>
/// <returns></returns>
protected bool Validate()
{
HasErrors = false;
_currentErrors.Clear();
if (ValidationErrors == null)
{
ValidationErrors = new ObservableCollection<string>();
}
ValidationErrors.Clear();
OnValidating();
foreach (var prop in this.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance))
{
foreach (var validation in prop.GetCustomAttributes<ValidationAttribute>())
{
if (!validation.IsValid(prop.GetValue(this)))
{
_currentErrors.Add(new KeyValuePair<string, string>(prop.Name, validation.ErrorMessage));
ValidationErrors.Add(validation.ErrorMessage);
}
}
HasErrors = _currentErrors.Count > 0;
RaiseError(prop.Name);
}
return !HasErrors;
}
/// <summary>
/// Inserts the specified property error (Use inside OnValidating).
/// </summary>
/// <param name="propName">Name of the property.</param>
/// <param name="error">The error.</param>
protected void InsertError(String propName, String error)
{
_currentErrors.Add(new KeyValuePair<string, string>(propName, error));
}
/// <summary>
/// Called before validating.
/// </summary>
protected virtual void OnValidating()
{
}
/// <summary>
/// Posts the specified message using the messenger service.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="message">The message.</param>
/// <returns></returns>
protected virtual T PostMessage<T>(T message)
{
TangoMessenger.Default.Send<T>(message);
return message;
}
/// <summary>
/// Registers a messenger message handler.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="handler">The handler.</param>
protected virtual void RegisterMessage<T>(Action<T> handler)
{
TangoMessenger.Default.Register<T>(handler);
}
}
/// <summary>
/// Represents an abstract view model which expects an <see cref="IView"/> of the specified type T.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <seealso cref="Tango.Core.ExtendedObject" />
/// <seealso cref="System.ComponentModel.INotifyDataErrorInfo" />
public abstract class ViewModel<T> : ViewModel where T : IView
{
/// <summary>
/// Gets or sets the view.
/// </summary>
public T View { get; set; }
/// <summary>
/// Initializes a new instance of the <see cref="ViewModel{T}"/> class.
/// </summary>
public ViewModel() : base()
{
TangoIOC.Default.GetInstanceWhenAvailable<T>((view) =>
{
View = view;
OnViewAttached();
});
}
/// <summary>
/// Called when the <see cref="IView"/> is loaded and attached.
/// </summary>
protected virtual void OnViewAttached()
{
}
}
}
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