String stands for
System.String and it is a .NET Framework type.
string is an alias in the C# language for
System.String.
Both of them are compiled to System.String in IL (Intermediate Language), so there is no difference. Choose what you like and use that. If you code in C#, I'd prefer string as it's a C# type alias and well-know by C# programmers.
I can say the same about (int, System.Int32) etc.. The complete list below..
- object: System.Object
- string: System.String
- bool: System.Boolean
- byte: System.Byte
- sbyte: System.SByte
- short: System.Int16
- ushort: System.UInt16
- int: System.Int32
- uint: System.UInt32
- long: System.Int64
- ulong: System.UInt64
- float: System.Single
- double: System.Double
- decimal: System.Decimal
- char: System.Char
There is one circumstance in which you have to use the aliases: when explicitly specifying an enum's underlying type. For instance:
public enum Foo : Int32 {} // Invalid
public enum Bar : int {} // Valid
