Odtnhj

Ive been researching and I am a little stuck on finding the right answer.

Lets say I have a c# class with auto properties. I want to have some of these properties calculated based of the properties that a user will change. I understand that you can use a constructor to do this calculation on creation of a new object.

What I am trying to find out is, in a web api does the class constructor get called on an update? Do i do the following or create customer setters?

eg

class myclass 
{
 public int Num1 get; set; 
 public int Num2 get; set; 
 public int Num3 get; set; 
 public int Num4 get; set; 

 //these get changed when values above get changed by API
 public int result1 get; set; 
 public int result2 get; set; 
 public int result3 get; set; 

 //constructor
 public myClass()
 {
 result1 = Num1 + Num2;
 result2 = Num3 + Num2;
 result3 = Num4 + Num2;
 

if I understand correctly, you simply need some derived readonly properties:

class myclass

 public myclass()
 

 

 public int Num1 get; set; 
 public int Num2 get; set; 
 public int Num3 get; set; 
 public int Num4 get; set; 


 public int result1 => Num1 + Num2;
 public int result2 => Num3 + Num2;
 public int result3 => Num4 + Num2;

What you need to use is INotifyPropertyChanged, see the minimal example below

void Main()

 var test = new myClass();
 test.Num1 = 1;
 test.Num2 = 2;
 test.Num3 = 3;
 test.Num4 = 4;

 test.result1.Should().Be(3);
 test.result2.Should().Be(5);
 test.result3.Should().Be(6);

 test.Num1 = 2;
 test.result1.Should().Be(4);
 test.Num2 = 0;
 test.result2.Should().Be(3);
 test.result3.Should().Be(4);


class myClass : INotifyPropertyChanged

 // private setter since these values are only being set when the numi are updated
 public int result1 get; private set; 
 public int result2 get; private set; 
 public int result3 get; private set; 

 public event PropertyChangedEventHandler PropertyChanged;
 public myClass()
 
 PropertyChanged += new PropertyChangedEventHandler(UpdateResultValue);
 

 private void UpdateResultValue(object sender, PropertyChangedEventArgs e)
 
 result1 = num1 + num2;
 result2 = num2 + num3;
 result3 = num2 + num4;
 

 protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
 
 PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
 

 protected bool SetField<T>(ref T field, T value, [CallerMemberName] string propertyName = null)
 
 if (EqualityComparer<T>.Default.Equals(field, value)) return false;
 field = value;
 OnPropertyChanged(propertyName);
 return true;
 

 private int num1;
 public int Num1
 
 get => num1;
 set => SetField(ref num1, value);
 

 private int num2;
 public int Num2
 
 get => num2;
 set => SetField(ref num2, value);
 

 private int num3;
 public int Num3
 
 get => num3;
 set => SetField(ref num3, value);
 

 private int num4;
 public int Num4
 
 get => num4;
 set => SetField(ref num4, value);