C#: How to compare variables by value and reference type

9y1kLearn iOS Programming

i have a small confusion that when we compare like == or equal function then both does the same job. u have a very basic question here.

see my program full code

int x = 1000;
int y = 1000;
if (x == y)
Console.WriteLine("Value is same");
else
Console.WriteLine("Value is not same");
if (x.Equals(y))
Console.WriteLine("Value is same");
else
Console.WriteLine("Value is not same");
if (object.ReferenceEquals(x,y))
Console.WriteLine("ref is same");
else
Console.WriteLine("ref is not same");
string s1 = "Hello";
string s2 = "Hello";
if (s1 == s2)
Console.WriteLine("Value is same");
else
Console.WriteLine("Value is not same");
if (s1.Equals(s2))
Console.WriteLine("Value is same");
else
Console.WriteLine("Value is not same");
if (object.ReferenceEquals(s1, s2))
Console.WriteLine("ref is same");
else
Console.WriteLine("ref is not same");

i know that this kind of checking if (x == y) is based on value but when i use Equals function then i saw Equals is also work like == operator....am i right ?

how to check the reference ?

if (object.ReferenceEquals(x,y))
Console.WriteLine("ref is same");
else
Console.WriteLine("ref is not same");

i saw in this case else portion execute........why because different memory is allocated for x and y ?
see more for string reference check

if (object.ReferenceEquals(s1, s2))
Console.WriteLine("ref is same");
else
Console.WriteLine("ref is not same");

in this scenario s1 and s2 ref found same which is not clear to me because s1 and s2 ref should be different because two are different variable so how s1 and s2 reference check become same?

i like to know what are the best process to know value and reference is same or not whatever data type we use may be string or integer or float etc. please some one help me to understand this.

one guy said string in dotnet is interned. what is the meaning of In .NET strings are interned ? interned or internal is same ?

please discuss with a example just to clarify the meaning of string is interned in dotnet.

thanks

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Dharmraj Thakur9y ago
Accepted answer
Remember, string is Immutable which means If you change value of string it will allocate new memory every time if it is not same as other variable....

If you change a vaiable 10 times then 10 time memory allocations will perform and if value will same as old variable then variable will not allocate and old variable's reference will be store...
Why String is Immutable :

http://stackoverflow.com/questions/2365272/why-net-string-is-immutable
http://www.c-sharpcorner.com/UploadFile/b1df45/string-is-immutable-in-C-Sharp/
9y ago
do you know what does mean string is interned in dotnet ?

please explain it if possible. thanks for answer.
9y ago
searching google i found if two different string variable hold same value then one memory will be allocated for two different variable for better memory optimization.

if it is true then if one variable value change then what will happen ?

string x = "good";
string y = "good";

in dotnet one memory will be allocated because two variable having same data. if later if i change value of y like y = "bye bye"; then what will happen ?

thanks
Dharmraj Thakur9y ago
Your solution is here...

Each string literal does not necessarily result in a new string instance. When two or more string literals that are equivalent according to the string equality operator (Section 7.9.7) appear in the same assembly, these string literals refer to the same string instance

http://stackoverflow.com/questions/10779422/two-different-strings-are-the-same-object-instance