How can I save the original state of my Model and its XAML bindings in C# in a Variable?

Tom Meier 180 Reputation points

I need to save the original state of my viewmodel and XAML bindings in C# when a View is originally loaded, so that I can revert back to the original Model property values if the user chooses to cancel their changes. I attempted to use the code below, but I realized that my variable tempCompanyInfo is still pointing to retModel after the changes, likely because CompanyInfo is a reference variable. Any suggestions on how I can properly save the original state?

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  1. Michael Taylor 50,426 Reputation points

    What you're looking for is the Memento pattern. This pattern allows you to "save" and "restore" changes to an object. It is popular with undo/redo situations.

    If you don't need this but in one case then really the best option is to pass to your view model the data you want to modify and have it copy the values it cares about into properties. Then bind the UX to the properties. When the user "cancels" then there is nothing you need to do. If they "save" then you copy the properties from the model back to the original object.

    If you really need a memento implementation then it is not hard to create your own interface and implementation. Because objects can vary wildly and what you may or may not want to save/restore can vary you'll end up having to implement this for each type you want to support it with. There are countless examples online on how to do this in C#. But I wouldn't go that route unless you really need the complexity.

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  2. Bruce ( 59,546 Reputation points

    object instance assignments are by ref.

    using System;
    public class Program
    	public class Test
    		public string Foo {get; set;} = "Foo";
    		public string Bar {get; set;} = "Bar";
    		public Test Clone() => new Test
    			Foo = this.Foo,
    			Bar = this.Bar
    	public static void Main()
    		var f1 = new Test();
    		var f2 = f1;
      		var f3 = f1.Clone();		
    		Console.WriteLine(f1.Foo); //Foo
    		f2.Foo = "Test";
    		Console.WriteLine(f1.Foo); //Test
    		Console.WriteLine(f3.Foo); //Foo

    you need to implement a clone for view model, or implement change tracking.

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