What is the difference between ref and out

Question

I'm new to C# and would like to know the difference between ref and out. -Mike

bilnaad · Answer

LOL :)

alobiuc · Answer

Ha! That's a good one...replying after almost a year!!!

jhtchina · Answer

ref: must first initialize before function Call; after return value by ref define. eample: from MSDN: using System; public class MyClass { public static void TestRef(ref char i) { // The value of i will be changed in the calling method i = 'b'; } public static void TestNoRef(char i) { // The value of i will be unchanged in the calling method i = 'c'; } // This method passes a variable as a ref parameter; the value of the // variable is changed after control passes back to this method. // The same variable is passed as a value parameter; the value of the // variable is unchanged after control is passed back to this method. public static void Main() { char i = 'a'; // variable must be initialized TestRef(ref i); // the arg must be passed as ref Console.WriteLine(i); TestNoRef(i); Console.WriteLine(i); } } out: b b out: must not initialize value.but need define before Call function. Example: using System; public class MyClass { public static int TestOut(out char i) { i = 'b'; return -1; } public static void Main() { char i; // variable need not be initialized Console.WriteLine(TestOut(out i)); Console.WriteLine(i); } } out: -1 b

prasad.narwadkar · Answer

ref: Used when you want the argument passed to a function to reflect the changes that occur to it inside that function. E.g. public void CloseDeviceManager(ref Form refToDevManager) {refToDevManager.Close();} could be called from a Form's method as public void Form2_Load { Form1 form1; CloseDeviceManager(ref form1) } The above code will close Form 1 while loading Form2. out: Is very similar to pointers in unmanaged enviroment. they could get intialized in the called function and also reflect the changes that occur to it inside the called function, in the calling function.

Administrator · Answer

ref : In C# Value types are passed by values and reference types are passed by reference.If you want to override this default behaviour and want to pass value type parameters as reference types then we need to use the "ref" keyword. out: in C# any variable referenced without initialization will raise a compile time error and if you use this keyword with a variable declaration you can reference it without initialization. to be brief : to reference a variable which is not initialized you will use "out" keyword

Administrator · Answer

I think ref is only for initialized parameters

What is the difference between ref and out

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Answers (6)