Is it possible to implement a immutable struct in c#

Question

class string is immutable. It is impossible implementing an immutable struct type as you can't disable or override assignment operation ( = ). Even you define a readonly struct you can always change the value of the struct type by using assignment operator. For example xy are values of a readonly struct. x = y; will change the content of x . So the readonly struct section in C# language reference is not correct. Is this right?

Jaish Mathews · Answer

You are correct in observing that the readonly struct does not prevent reassignment. This is by design: readonly struct only ensures that the fields of the struct cannot be directly modified . It does not make the variable (the reference to the struct) immutable. readonly struct Point { public readonly int X { get; } public readonly int Y { get; } public Point(int x int y) { X = x; Y = y; } } In above defined structure if you create references as Point p1 = new Point(1 2); Point p2 = new Point(3 4); Then p1.X = 100; // Invalid p1 = p2; // Valid. Entirely replaces the instance not its fields. To create true immutability  you can try: A readonly struct . A readonly field or property to hold the struct ifield n a class. So the implementation should be different using a class and your program only use that class to acess the structure. class ImmutableStructHolder { public readonly Point PointValue; public ImmutableStructHolder(Point point) { PointValue = point; } } Then var holder = new ImmutableStructHolder(new Point(1 2)); // Valid holder.PointValue = new Point(3 4); // Error: Cannot assign to readonly field.

Leo Qiao · Answer

Thank you for great response. That is what I meant.