Allow field or property values to be assigned directly from the constructor parameters

[serhiisolodovnyk]

I would like to be able to assign fields and properties in the constructor directly from the parameters. I know that a primary constructor can be a good solution, but sometimes we can't use a primary constructor (for example, when we need to add the [JsonConstructor] attribute to the constructor, etc.):

public class Car
{
    // current syntax
    public Car(string brand, string model, string color, decimal price)
    {
        Brand = brand;
        Model = model;
        Color = color;
        Price = price;
    }

    // optimal syntax
    public Car(this.Brand, this.Model, this.Color, this.Price)
    {
    }

    public string Brand { get; set; }

    public string Model { get; set; }

    public string Color { get; set; }

    public decimal Price { get; set; }
}

This feature was also implemented in Dart with the same syntax:

class Car {

        String make;
  	String model;
  	String yearMade;
  	bool hasABS;
  
  	Car(this.make, this.model, this.yearMade, this.hasABS);
}

[yaakov-h]

Records or primary constructors with #3650 / #7047 seem like they would solve this issue in a better way IMO.

[DavidArno]

As of next week, with the release of .NET 8 and C# 12, you will be able to use primary constructors to express that as:

public class Car(string brand, string model, string color, decimal price)
{
    public string Brand { get; set; } = brand;
    public string Model { get; set; } = model;
    public string Color { get; set; } = color;
    public decimal Price { get; set; } = price;
}

If you have concerns over this feature, such as the ability to use Json attributes, or you'd prefer to eg be able to express that as:

public class Car(
    string Brand { get; set; },
    string Model { get; set; },
    string Color { get; set; },
    decimal Price { get; set; })

Then head over to #7667 and request it there as Microsoft are actively asking for feedback on this feature.

[serhiisolodovnyk]

well, thank you. I discovered that C# 12 will provide the ability to add an attribute to the primary constructor: https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/instance-constructors#primary-constructors