Pass by Value in C#

Question

How can I pass an object of a "MyClass" (C#) by Parameter-by-Value to a method? example:

MyClass obj = new MyClass();
MyClass.DontModify(obj); //Only use it!
Console.Writeline(obj.SomeIntProperty);

...

public static void DontModify(MyClass a)
{
    a.SomeIntProperty+= 100;// Do something more meaningful here
    return;
}

Answer 1

By default object types are passed by value in C#. But when you pass a object reference to a method, modifications in the object are persisted. If you want your object to be inmutable, you need to clone it.

In oder to do it, implement the ICloneable interface in your class. Here is a mock example of how to use ICloneable:

public class MyClass : ICloneable
{
  private int myValue;

  public MyClass(int val)
  {
     myValue = val;
  }

  public void object Clone()
  {
     return new MyClass(myValue);
  }
}

Answer 2

By default, it is passed by value. However, you're passing the object reference by value, which means you can still edit values within the object.

In order to prevent the object from being able to change at all, you would need to actually clone the object prior to passing it into your method. This would require you to implement some method of creating a new instance that is a copy of your original object, and then passing in the copy.

Answer 3

public static void DontModify(MyClass a)
{
    MyClass clone = (MyClass)a.Clone();
    clone.SomeIntProperty+= 100;// Do something more meaningful here
    return;
}

Answer 4

You could create a Clone method on your object to pass the return value to your method. C# cannot pass reference types by value so this might be a good alternative.

public MyClass CreateClone()
{
    return new MyClass() { SomeIntProperty = this.SomeIntProperty };
}