What is the difference between ref and out parameters in C#?

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Deepika Sawant · Answer

ref Keyword Purpose : Passes a variable by reference , allowing the method to read and modify its value. Initialization Requirement : The variable must be initialized before being passed. Use Case : When the method needs to read and update the value. Direction : Bi-directional —data flows into and out of the method. void UpdateName(ref string name) { name = "UpdatedName"; } string myName = "OriginalName"; UpdateName(ref myName); Console.WriteLine(myName); // Output: UpdatedName out Keyword Purpose : Also passes a variable by reference , but it's used to output data from a method. Initialization Requirement : The variable does not need to be initialized before being passed. Use Case : When the method needs to return multiple values . Direction : Uni-directional —data flows only out of the method. void GetCoordinates(out int x, out int y) { x = 10; y = 20; } int x, y; GetCoordinates(out x, out y); Console.WriteLine($"X: {x}, Y: {y}"); // Output: X: 10, Y: 20 Feature ref out Must be initialized? Yes No Must be assigned in method? No Yes Data flow In and Out Out only Common use case Modify existing value Return multiple outputs

Sandhiya Priya · Answer

Difference Between ref and out in C# Both ref and out keywords allow you to pass arguments by reference to a method, meaning the method can modify the original variable. However, they have key differences: Feature ref out Initialization before call Must be initialized before passing to the method No need to initialize before passing; method must assign it before returning Purpose Pass an existing variable by reference Return multiple values from a method Assignment inside method Optional Mandatory – the method must assign a value before it returns Use case When you want to read and write the variable inside the method When you only want to write a value inside the method and return it Declaration in method void MyMethod(ref int x) void MyMethod(out int x) Example See below See below Example of ref void Increment(ref int number) { number += 5; // modifies original variable } int a = 10; Increment(ref a); Console.WriteLine(a); // Output: 15 a must be initialized before passing to the method. Example of out void GetValues(out int x, out int y) { x = 100; // must assign before returning y = 200; } int p, q; GetValues(out p, out q); Console.WriteLine($"p = {p}, q = {q}"); // Output: p = 100, q = 200 p and q don’t need initialization before the method call, but the method must assign values . Key Points Use ref when the variable already has a value and you want to pass it by reference . Use out when the method needs to return multiple values or initialize a variable .

What is the difference between ref and out parameters in C#?

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