The difference between String and string?

There should be NO difference. Please show us the relevant code for better help.
:-)

Some answers here are correct, some are not.
Right answers are the ones which say there is no difference. You can use System.String anywhere you can use string and visa versa.

More exactly, "string" is a keyword backed by System.String (alias).

Now, I can give you one reason why you may prefer string over String: The code "System.String" is longer, but just "String" may not compile, because you may choose not to add "using System" (I often avoid some using it), but "string" will always work. Same things about "System.Object" vs "object", the later is better.

—SA

go this links
http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/7e62b4cf-0d78-4243-936c-8b0f4240676c/[^]

http://stackoverflow.com/questions/7074/in-c-what-is-the-difference-between-string-and-string[^]
http://stackoverflow.com/questions/215255/string-vs-string-in-c[^]

Depends on how long the string is.

AFAIK, string represents working with instances where as String represents the class itself.
If you are using instance variables, you might as well use string.

There isn't any defference...
wherever you use string variable = "some string"; at that time actually you are creating an instance of String class. string is immutable so it can't be alter once it create, by means if you want to change any data or any portion of that string, then it will create new object of String class any it will assign to the same reference...

suppose

string s = "good morning"; // it is equivalent to String s = new String("good morning");
s = "good noon"; //here new object will be created of String Class and will be assigned to reference variable named s and old object will no longer referred by any reference variable so garabase collector will remove it.