Check for changed properties in WPF MVVM Binding - mvvm

Question

I'm binding properties from an object like this:
ViewModel:
public class VieModel
{
public Model MyModel
{
get
{
return myModel;
}
set
{
myModel = value;
}
}
private Model myModel
}
Model:
public class Model
{
public string Name { get; set;}
public string Info { get; set;}
public string MoreInfo { get; set;}
}
View:
<TextBox Text="{Binding MyModel.Name, Mode=TwoWay, Mode=TwoWay, UpdateSourceTrigger=LostFocus }" />
<TextBox Text="{Binding MyModel.Info, Mode=TwoWay, UpdateSourceTrigger=LostFocus }" />
<TextBox Text="{Binding MyModel.MoreInfo, Mode=TwoWay, UpdateSourceTrigger=LostFocus }" />
Everything is working fine but when MyModel changes, I would like to check if any property has changed so I can ask the user to save first.
So my first thought was to add a boolean which turns to true on any change so I can check for that in the setter of MyModel. But currently I don't get a notification on MyModel when I change a Property even though it does in the background..
All in all i get it, cause MyModel does not really change.. but how do i detect any a change on any property?
Thanks in advance! :)
Answer:
To check if the current MyModel is the same as the old one u need to store copy of that object to be able to compare them as described by Bijington here
For that you can do it manually or use a Binary-Serializer so you can clone your mobject.
manually:
public class Model
{
public string Name { get; set;}
public string Info { get; set;}
public string MoreInfo { get; set;}
public static Model Clone(Model obj)
{
Model newModel = new Model();
newModel.Name = obj.Name;
newModel.Info = obj.Info;
newModel.MoreInfo = obj.MoreInfo;
return newModel;
}
}
BinaryFormatter.Serialize:
You need EVERY object used in you Model to have the [Serializable] attribute.
[Serializable]
public class Model
{
public string Name { get; set;}
public string Info { get; set;}
public string MoreInfo { get; set;}
public SecondModel SecondOne { get; set;}
public static Model Clone(Model obj)
{
using (var ms = new MemoryStream())
{
var formatter = new BinaryFormatter();
formatter.Serialize(ms, obj);
ms.Position = 0;
return (T)formatter.Deserialize(ms);
}
}
}
[Serializable]
public class SecondModel
{
public string SecondName { get; set;}
public string SecondInfo { get; set;}
public string SecondMoreInfo { get; set;}
}

Answer 1

I have slightly changed my approach from the initial comment. Instead of implementing IComparer the option I have gone with is to override the Equals method.
public class Model
{
public string Name { get; set; }
public string Info { get; set; }
public string MoreInfo { get; set; }
public override bool Equals(object obj)
{
if (obj is Model model)
{
return string.Equals(this.Name, model.Name, StringComparison.Ordinal);
// && Add your other property comparisons here...;
}
return false;
}
public override int GetHashCode()
{
// You really should provide your implementation here:
return base.GetHashCode();
}
}
Then once you have set up the Model class like the above you can do the checks inside your ViewModel class:
public class VieModel
{
private Model myModel;
public Model MyModel
{
get
{
return myModel;
}
set
{
if (myModel?.Equals(value) != true)
{
// The model has changed so you can perform what you want here...
myModel = value;
}
}
}
}