C # string manipulation (i)

In C # built-in types, strings are unique reference types with immutability and tightness.

Non-denaturing refers to a string once created, it cannot be changed, STR1=STR1, actually creates a new Str1 string object in the heap, and returns a reference to the object.

Sealing refers to a string that cannot be inherited.

Immutability and sealing performance guarantees a more efficient and secure string type.

String manipulation

1. Formatting strings

String.Format

 string  str1 =  " puguo 2530    string  Strformat =  " {0,20}  ; //   string formatting takes 20 characters  string  strresult=.  Format (STRFORMAT,STR1); Console.WriteLine (  string. Format ({0},{1}) =[{2}]\n  , Strformat,str1,strresult); 

Standard Numeric formatted string	Meaning	Instance
C or C	Currency	String. Format ("{0:c}", 10) =￥10.00
D or D	Fill-In	String. Format ("{0:d3},10") =010
E or E	Index	String. Format ("{0:e3},10") =1.000e+001
F or F	Fixed point	String. Format ("{0:f3},10") =10.000
G or G	Conventional	String. Format ("{0:g3},10") =10
N or N	thousand-minute character	String. Format ("{0:n},10000") =10,000.00
P or P	Percent Sign	String. Format ("{0:p},1") =100%
X or X	16 System	String. Format ("{0:x}", 1900) =96c

Custom Numeric formatting strings	Meaning
0	0 placeholder
#	Digit placeholder
.	Decimal point
，	Thousands separator
；	Segment Separator
%	Percent symbol

2. Comparing strings

(1), String.Compare (STR1,STR2)

STR1<STR2--->-1

STR1==STR2--->0

STR1>STR2--->1

(2), string.compareordinal (STR1,STR2); Unlike (1), which is not related to localization

STR1<STR2--->-1

STR1==STR2--->0

STR1>STR2--->1

(3), Str1.compareto (STR2);

STR1<STR2--->-1

STR1==STR2--->0

STR1>STR2--->1

STR2 is null--->1 "" greater than null

(4), String. Equals (str1, str2) <==> str1==str2

STR1==STR2--->0

str1! =STR2--->!0

(5), str1. Equals (STR2)

STR1==STR2--->0

str1! =STR2--->!0

(6), STR1==STR2

Summary: Static methods are more efficient than instance methods because static methods are loaded first than instance methods. Overall, (1) (2) ratio (3) Good, (4) than (5) good

3. String connection

(1), STR1+STR2

(2), String. Concat (STR1,STR2)

4. Copying strings

(1), str2=string. Copy (STR1);

Copy creates a new instance string object, and Str2,str1 does not point to the same string reference.

(2), STR2=STR1

Copy directly, str2 and str1 point to the same string reference. The immutability of the string causes the reference to the string to be immutable, changing the string reference to the string referenced by the string.

(3), str2= (String) Str1.clone ()

Str1.clone () Returns the object type, which is coerced to string and is consistent with the (2) effect.

C # string manipulation (i)