What is the difference between String and string in C#?

What is the difference between String and string in C#?

Both string and String are functionally equivalent in C#, and you can use them interchangeably. They both refer to the same underlying type in the .NET runtime.

For example:

string message = "Hello, World!";
String message = "Hello, World!";

It is generally recommended to use string when declaring variables, as it is simpler and more consistent with other primitive types like int, bool, etc.

For example:

string place = "world";

It is generally recommended to use String when specifically referring to the class in C#.

For example:

string greet = String.Format("Hello {0}!", place);

string is a C# keyword and is an alias for the System.String class.

String is the fully qualified name of the System.String class.

There is no functional difference, and the choice of which to use is mainly a matter of style and convention, with string preferred for variable declarations and String used for static methods or type references.