Why would you use String.Equals over ==? [duplicate]

It's entirely likely that a large portion of the developer base comes from a Java background where using == to compare strings is wrong and doesn't work.

In C# there's no (practical) difference (for strings) as long as they are typed as string.

If they are typed as object or T then see other answers here that talk about generic methods or operator overloading as there you definitely want to use the Equals method.

There is practical difference between string.Equals and ==

bool result = false;

object obj = "String";    
string str2 = "String";
string str3 = typeof(string).Name;
string str4 = "String";
object obj2 = str3;

// Comparision between object obj and string str2 -- Com 1
result = string.Equals(obj, str2);// true
result = String.ReferenceEquals(obj, str2); // true
result = (obj == str2);// true

// Comparision between object obj and string str3 -- Com 2
result = string.Equals(obj, str3);// true
result = String.ReferenceEquals(obj, str3); // false
result = (obj == str3);// false

// Comparision between object obj and string str4 -- Com 3
result = string.Equals(obj, str4);// true
result = String.ReferenceEquals(obj, str4); // true
result = (obj == str4);// true

// Comparision between string str2 and string str3 -- Com 4
result = string.Equals(str2, str3);// true
result = String.ReferenceEquals(str2, str3); // false
result = (str2 == str3);// true

// Comparision between string str2 and string str4 -- Com 5
result = string.Equals(str2, str4);// true
result = String.ReferenceEquals(str2, str4); // true
result = (str2 == str4);// true

// Comparision between string str3 and string str4 -- Com 6
result = string.Equals(str3, str4);// true
result = String.ReferenceEquals(str3, str4); // false
result = (str3 == str4);// true

// Comparision between object obj and object obj2 -- Com 7
result = String.Equals(obj, obj2);// true
result = String.ReferenceEquals(obj, obj2); // false
result = (obj == obj2);// false

Adding Watch

obj     "String" {1#}   object {string}
str2    "String" {1#}   string
str3    "String" {5#}   string
str4    "String" {1#}   string
obj2    "String" {5#}   object {string}

Now look at {1#} and {5#}

obj, str2, str4 and obj2 references are same.

obj and obj2 are object type and others are string type

Conclusion:

1. com1: result = (obj == str2);// true
   • compares object and string so performs a reference equality check
   • obj and str2 point to the same reference so the result is true
2. com2: result = (obj == str3);// false
   • compares object and string so performs a reference equality check
   • obj and str3 point to the different references so the result is false
3. com3: result = (obj == str4);// true
   • compares object and string so performs a reference equality check
   • obj and str4 point to the same reference so the result is true
4. com4: result = (str2 == str3);// true
   • compares string and string so performs a string value check
   • str2 and str3 are both "String" so the result is true
5. com5: result = (str2 == str4);// true
   • compares string and string so performs a string value check
   • str2 and str4 are both "String" so the result is true
6. com6: result = (str3 == str4);// true
   • compares string and string so performs a string value check
   • str3 and str4 are both "String" so the result is true
7. com7: result = (obj == obj2);// false  - compares object and object so performs a reference equality check      - obj and obj2 point to the different references so the result is false