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c#language-designc#-7.2

Purpose of "in" parameters in C#

C# 7.2 introduced in parameters for methods. I understand how they work:

int MyMethod(in int i) {
    i += 1; // illegal, i is read-only
    return i + 1;
}

I undestand that these parameters are passed by reference (like ref and out).

What I don't understand is the purpose of the in parameters. What do I gain by using them?
I understand the purpose of out and ref parameters, it is quite useful to be able to assign values to variables in the calling scope, but that function is non-existant with the in parameters.

Solution

  • "in" Can be used to pass a variable as a read-only reference (value type and reference type both). Reason to pass read-only reference is that, if I pass a value type variable without reference, then each time a new copy will be created. So, it will take extra memory and performance will be slower.