logofx-client-mvvm-model

Model objects with various aspects, including property change notification, hierarchical change tracking, error management, undo-redo stack capabilities.

Living documentation

Get package

Below you can find examples of most frequent use cases:

Property notification

using LogoFX.Client.Mvvm.Model;

public class MyModel : Model<int>
{
  private int _myField;
  public int MyProperty
  {
    get
    {
      return _myField;
    }
    set
    {
      _myField = value;
      NotifyOfPropertyChange();
    }
  }
}

In this case you get out-of-the-box support for property change notification without the need of explicit property name mentioning.

Validation and Errors

using System;
using System.ComponentModel.DataAnnotations;
using LogoFX.Client.Mvvm.Model;

public class NumberValidation : ValidationAttribute
    {
        public NumberValidation()
        {
            Minimum = int.MinValue;
            Maximum = int.MaxValue;
        }

        public int Minimum { get; set; }

        public int Maximum { get; set; }

        protected override ValidationResult IsValid(object value, 
                              ValidationContext validationContext)
        {
            var number = (int) value;

            if (number < Minimum || number > Maximum)
            {
                return new ValidationResult(ErrorMessage);
            }

            return ValidationResult.Success;
        }
    }
    
internal sealed class WarehouseItem : Model<Guid>, IWarehouseItem
    {
        public WarehouseItem(
            string kind, 
            double price, 
            int quantity)
        {
            Id = Guid.NewGuid();
            _kind = kind;
            _price = price;
            _quantity = quantity;            
        }

        private string _kind;        
        public string Kind
        {
            get { return _kind; }
            set
            {                
                _kind = Value;
                NotifyOfPropertyChange();
            }
        }

        private double _price;        
        public double Price
        {
            get { return _price;}
            set
            {
                NotifyOfPropertyChange();
                NotifyOfPropertyChange(() => TotalCost);
            }
        }

        private int _quantity;
        [NumberValidation(Minimum = 1, ErrorMessage = "Quantity must be positive.")]
        public int Quantity
        {
            get { return _quantity; }
            set
            {                
                _quantity = value;
                NotifyOfPropertyChange();
                NotifyOfPropertyChange(() => TotalCost);
            }
        }        

        public double TotalCost
        {
            get { return _quantity*_price; }
        }
    }

In this case when the value of Quantity is modified the validation execution mechanism is applied and all respective attributes are visited. The model itself has property Errors which is immediately populated with the resulting error messages if any. The property HasError will also reflect the current state of the errors inside the model.

In addition to client-side validation there is also ability to manage server-side validation and store the respective errors in the underlying model:

//...
var model = new MyModel();
var externalErrors = GetExternalErrors(myModel);
foreach(var error in externalErrors)
{
  model.SetError(error.Message, error.Property);
}

The "external" errors are displayed along with the others inside the Errors property.

By default the indexed error property and the single Error property return the list of errors as a single value, separated by new line. You can override this behaviour and supply your own implementation of errors presentation

using System.Collections.Generic;
using System.Linq;
using LogoFX.Client.Mvvm.Model;

public class MyModel : Model<Guid>
{
  protected override string CreateErrorsPresentation(IEnumerable<string> errors)
  {
    return errors.OrderBy(t => t.Length).Join(";");
  }
}

This repository is archived. Its functionality has been moved to https://github.com/LogoFX/mvvm