C＃.Net不区分大小写的字符串

Question

Why does C#.Net allow the declaration of the string object to be case-insensitive?

String sHello = "Hello";
string sHello = "Hello";

Both the lower-case and upper-case S of the word String are acceptable and this seems to be the only object that allows this.

Can anyone explain why?

Answer 1

string is a language keyword while System.String is the type it aliases.

Both compile to exactly the same thing, similarly:

• int is System.Int32
• long is System.Int64
• float is System.Single
• double is System.Double
• char is System.Char
• byte is System.Byte
• short is System.Int16
• ushort is System.UInt16
• uint is System.UInt32
• ulong is System.UInt64

I think in most cases this is about code legibility - all the basic system value types have aliases, I think the lower case string might just be for consistency.

Answer 2

Further to the other answers, it's good practice to use keywords if they exist.

Eg you should use string rather than System.String .

Answer 3

"String" is the name of the class. "string" is keyword that maps this class.

it's the same like

• Int32 => int
• Decimal => decimal
• Int64 => long

... and so on...

Answer 4

"string" is a C# keyword. it's just an alias for "System.String" - one of the .NET BCL classes.

Answer 5

“字符串”只是系统命名空间中类“字符串”的C＃别名。

Answer 6

I use String and not string, Int32 instead of int, so that my syntax highlighting picks up on a string as a Type and not a keyword. I want keywords to jump out at me.

Answer 7

string is an alias for System.String. They are the same thing.

By convention, though, objects of type (System.String) are generally refered to as the alias - eg

string myString = "Hello";

whereas operations on the class use the uppercase version eg

String.IsNullOrEmpty(myStringVariable);