Parameter modifiers
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ref
Pass a parameter by reference.
// value type var i = 10; Method0(i); // 10 Method1(ref i); // 11 void Method0(int i) => i++; // pass the value type parameter by value (copy) void Method1(ref int i) => i++; // pass the value type parameter by reference // reference type var item = new Item("init name"); Method2(item); // init name Method3(ref item); // new name 3 // pass the reference type parameter by value: the reference is passed by value (copy) // if the parameter is overwritten (the copy of the reference is overwritten), it doesn't affect the initial object void Method2(Item item) => item = new("new name 2"); // pass the reference type parameter by reference: the reference is passed by reference // if the parameter is overwritten (the initial reference is overwritten), it does affect the initial object void Method3(ref Item item) => item = new("new name 3"); |
ref readonly
Pass a parameter by reference and make it readonly.
Useful when you have a big value type and you want to pass only its reference for performances reason, but you don't want it to be overwritten.
var bigStruct = new BigStruct("name"); Method(ref bigStruct); void Method(ref readonly BigStruct bigStruct) { bigStruct = new BigStruct("new name"); // you can't assign a readonly variable bigStruct.Name = "new name"; // you can modify the object properties } |
If the variable is a readonly variable, you must use the in modifier while calling the method. |
in
Create a temporary variable for the argument and pass a readonly reference to that argument.
var i = 10; Method(in i); // in is optional in th calling method void Method6(in int i) // readonly copy of the initial parameter { i = 5; // you can't assign a readonly variable } |
out
Allow to initialize the parameter in the method.
Method5(out var j); // 5 void Method5(out int i) => i = 5; |