You can use theout keyword in two contexts:

• As aparameter modifier, which lets you pass an argument to a method by reference rather than by value.

• Ingeneric type parameter declarations for interfaces and delegates, which specifies that a type parameter is covariant.

Theout keyword is especially useful when a method needs to return more than one value since more than oneout parameter can be used e.g.

    public void Main()    {        double radiusValue = 3.92781;        //Calculate the circumference and area of a circle, returning the results to Main().        CalculateCircumferenceAndArea(radiusValue, out double circumferenceResult, out var areaResult);        System.Console.WriteLine($"Circumference of a circle with a radius of {radiusValue} is {circumferenceResult}.");        System.Console.WriteLine($"Area of a circle with a radius of {radiusValue} is {areaResult}.");        Console.ReadLine();    }    //The calculation worker method.    public static void CalculateCircumferenceAndArea(double radius, out double circumference, out double area)    {        circumference = 2 * Math.PI * radius;        area = Math.PI * (radius * radius);    }

The following limitations apply to using theout keyword:

• out parameters are not allowed in asynchronous methods.
• out parameters are not allowed in iterator methods.
• Properties cannot be passed asout parameters.