C#

public class Toy
{
   // changing the ID is probably NOT a good idea.
   // put it onto the constructor
   public Toy(int id)
   {
     ID = id;
   }
   public int ID { get; private set; }
   // unless you need ID to be a property (like for data binding)
   // this might be a case for a public readonly field:
   // public readonly int ID;
   public double Price { get; set; }
   public string Color { get; set; }
}

public class Merchandise
{
  public Dictionary<int, Toy> toys;
  public Merchandise()
  {
    var toyList = new List<Toy>();
    // presumably you're actually loading the real data from some other source...
    toyList.Add(new Toy {ID = 1, Price = 10, Color = "Red"});
    toyList.Add(new Toy {ID = 2, Price = 10, Color = "White"});
    toyList.Add(new Toy {ID = 3, Price = 10, Color = "Black"});
    toys = toyList.ToDictionary(t => t.ID);
  }
  
  public string this[int toyId]
  {
   get 
     {
       Toy theToy;
       toys.TryGetValue(toyID, out theToy); // In this case we can ignore the return value
       return theToy;
     }
  }      
}

// this is CLEARLY going to fail!
// You need to use double.TryParse(txtPrice.Text, ...) with appropriate error handling
// to convert it from a string to a double!!!!!
public double price = txtPrice.Text;
public string color = txtColor.Text;
 
public Merchandise item = new Merchandise();
// Before you reference the .Price or .Color properties, 
// you need to validate that item[2] didn't return null!!!

// What you had:

//Change Price Dynamically
// item[2, "Price"].Price = price;
// this  ^^^^^^^^^ was pointless since passing the property name to the indexer didn't accomplish anything
item[2].Price = price;  // with my indexer definition
 
//Change Color Dynamically
// item[2, "Color"].Color = color;
// again ^^^^^^^^^ pointless
item[2].Color = color;

// Instead, more like:
Toy theToy = item[2];
if (theToy != null)
{
  //Change Price Dynamically
  theToy.Price = price;
  //Change Color Dynamically
  theToy.Color = color;
}
else
{
  // report the no such toy with that ID error !!
}

public string this[int toyId, string price, string color]
{
     get
     {
      string result = string.Empty;
       if (color != null)
       {
          result = toyList.FirstOrDefault(toy => toy.ID == toyId).Color;
       }
          else if (price != null)
       {
          result = (toyList.FirstOrDefault(toy => toy.ID == toyId).Price).ToString();
       }
       return result;
    }
    set
    {
       if (color != null)
       {
            toyList.FirstOrDefault(toy => toy.ID == toyId).Color = value;
       }
       else if (price != null)
       {
          toyList.FirstOrDefault(toy => toy.ID == toyId).Price = Convert.ToDouble(value);
       }
    }
}

List<Toy> toys = new List<Toy>();
toys.Add( new Toy() { Id = 1, Color = "Red", Price = 1.20M } );
toys.Add( new Toy() { Id = 2, Color = "Red", Price = 1.20M } );
toys.Add( new Toy() { Id = 3, Color = "Red", Price = 1.20M } );

toys.Single( o => o.Id == 2 ).Color = "Blue";
toys.Single( o => o.Id == 2 ).Price = 3.99M;

toys.ForEach( o => Console.WriteLine( $"{o.Id} {o.Color} {o.Price}" ) );

saeedmir wrote:

FileWatcher can catch registry keys?

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

• the first involved late loading with LoadLibrary from c# ...
• the second involved modify the dll search path using ? SetDllDirectory

Nathan Minier wrote:

The best you can hope for is to make the cost of acquisition higher than the value of acquisition.

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]