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using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Tango.Core;
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(); }
}
/// <summary>
/// Occurs when the validation errors have changed for a property or for the entire entity.
/// </summary>
public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;
/// <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()
{
OnValidating();
HasErrors = false;
_currentErrors.Clear();
foreach (var prop in this.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance))
{
foreach (var validation in prop.GetCustomAttributes<ValidationAttribute>())
{
if (!validation.IsValid(prop.GetValue(this)))
{
HasErrors = true;
_currentErrors.Add(new KeyValuePair<string, string>(prop.Name, validation.ErrorMessage));
RaiseError(prop.Name);
}
}
}
return !HasErrors;
}
/// <summary>
/// Called before validating.
/// </summary>
protected virtual void OnValidating()
{
}
}
/// <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>
/// <param name="view">The view.</param>
public ViewModel(T view)
{
View = view;
View.ViewAttached += (x, e) =>
{
View = (T)e;
OnViewAttached();
};
}
/// <summary>
/// Initializes a new instance of the <see cref="ViewModel{T}"/> class.
/// </summary>
/// <param name="view">The view.</param>
/// <param name="delayed">if set to <c>true</c> waits for the view to be valid before registering for the <see cref="IView.ViewAttached"/> event.</param>
public ViewModel(T view, bool delayed)
{
Task.Factory.StartNew(() =>
{
while (view == null)
{
Thread.Sleep(10);
}
}).ContinueWith((c) =>
{
View = view;
View.ViewAttached += (x, e) =>
{
View = (T)e;
OnViewAttached();
};
});
}
/// <summary>
/// Called when the <see cref="IView"/> is loaded and attached.
/// </summary>
protected virtual void OnViewAttached()
{
}
}
}
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