How to use the method of C # string String and character Char
This article mainly introduces the C# string String and character Char method of how to use the relevant knowledge, the content is detailed and easy to understand, the operation is simple and fast, has a certain reference value, I believe that you read this C# string String and character Char method how to use the article will have a harvest, let's take a look at it.
1. String: 1. Access the characters in String:
String itself can be thought of as an array of Char.
String s = "hello world"; for (int I = 0; I < s.Lengthi +) {Console.WriteLine (s [I]);} / or foreach (char c in s) {Console.WriteLine (c);}
Break into an array of characters (ToCharArray)
String s = "Hello World"; char [] arr = s.ToCharArray (); / / Console.WriteLine (arr [0]); / / outputs the first element of the array, outputting "H" 2, truncated substring: Substring (startIndex, [length]), including the characters at startIndex. String s = "hello world"; Console.WriteLine (s.Substring (3)); / / lo worldConsole.WriteLine (s.Substring (3,4)); / / lo w3. Find substrings: IndexOf (subString), LastIndexOf (subString), Contains (subString) string s = "hello world"; Console.WriteLine (s.IndexOf ("o")); / / 4Console.WriteLine (s.LastIndexOf ("o")); / / 7Console.WriteLine (s.IndexOf ('l')) / / find the position of the first occurrence of'l' in the string 2Console.WriteLine (s.IndexOf ('lags, 4)); / / find the position of the fourth occurrence of' l' in the string 9Console.WriteLine (s.IndexOf ('lure, 5,6)); / / locate the position of the occurrence of' l' between the fifth bit and the next six digits in the string 9Console.WriteLine (s.Contains ("e")); / / True4, fill the substring to the specified length: PadLeft (totalLength,char), PadRight (totalLength,char) string s = "hello world"; Console.WriteLine (s.PadLeft (15,'*)); / / * hello worldConsole.WriteLine (s.PadRight (15,'*')); / / hello world****5, convert case: ToUpper (), ToLower () string s = "Hello World" Console.WriteLine (s.ToUpper ()); / / HELLO WORLDConsole.WriteLine (s.ToLower ()); / / hello world6, delete the string fragment at the specified position of the string: Remove (startIndex,length) string s = "Hello World"; Console.WriteLine (s.Remove (7)); / / Hello WConsole.WriteLine (s.Remove (7Power1)); / / Hello Wrld7, replace substring: Replace (oldStr,newStr) string s = "Hello World"; Console.WriteLine ("l", "*")) / / He**o Wor*dConsole.WriteLine (s.Replace ("or", "*")); / / Hello W*ld8, remove leading and trailing spaces or specified characters: Trim (), TrimStart (), TrimEnd () string s = "Hello World"; Console.WriteLine (s.Trim ()); / / "Hello World" Console.WriteLine (s.TrimStart ()); / / "Hello World" Console.WriteLine (s.TrimEnd ()); / / "Hello World" string S1 = "hello Worldhd" Console.WriteLine (s1.Trim); / ello WorlConsole.WriteLine (s1.TrimStart); / ello WorldhdConsole.WriteLine (s1.TrimEnd); / / hello Worl9, insert characters before index: Insert (index,str) string s = "Hello World"; Console.WriteLine (s.Insert (6, "test")) / / Hello tests World10, splits the string into some special character (string), and returns an array of strings: Split (char/char [] / string [], [StringSplitOptions] string s = "Hello World"; Console.WriteLine (s.Split ('o')); / / "Hell", "W", "rld" Console.WriteLine (s.Split ('eBay,' d')) / / "H", "llo Wor l", "Console.WriteLine (s.Split (new string [] {"}, StringSplitOptions.None)); / /" Hello "," Wor ","," ld "," Console.WriteLine (s.Split (new string [] {"}, StringSplitOptions.RemoveEmptyEntries)); / /" Hello "," Wor "," ld "foreach (string sub in s.Split ('o')) {Console.WriteLine (sub) } 11. String merging
1. String.Concat (str1, str2, … ., strn): concatenates n strings with no connector in the middle. String concatenation can also be implemented with'+'.
2. String list (string [], IEnumerable) is concatenated with str, and the static function Join (SplitCh, array)
String [] arr = {"Hello", "World"}; Console.WriteLine (string.Join ("*", arr)); / / Hello*World
3. Instance method StringBuilder.Append
StringBuilder sb = new StringBuilder (); / / declare a string constructor instance sb.Append ("A"); / / use string constructor to connect strings for higher performance sb.Append ('B'); Console.WriteLine (sb.ToString ()); / / output "AB" 12, formatting, static function Format (placeholder, variable) string s = "Hello World" Console.WriteLine (string.Format ("I Love\" {0}\ ", s)); / / I Love" Hello World "Console.WriteLine (string.Format (" {0Love C} ", 120.2)); / / ¥120.20Console.WriteLine (string.Format (" {0: yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy
1. Int32.TryParse (string,out bool): always does not throw an exception and returns true/false to indicate whether the parsing is successful. String returned unsuccessful parsing for null.
Int ret = 0 if (int.TryParse ("120.5", out ret)) / / conversion exception! {Console.WriteLine (ret);} else {Console.WriteLine ("conversion exception!") ;}
2. Int32.Parse (string): an exception will be thrown if the parsing is not successful. Throws a "value cannot be null. Parameter name: String" exception when string is null.
Try {Console.WriteLine (int.Parse ("120.5")); / / incorrect format of input string} catch (Exception e) {Console.WriteLine (e.Message);}
3. Convert.ToInt32 (string): an exception will be thrown if the parsing is not successful, but 0. 0 will be returned if the string is null.
Try {Console.WriteLine (Convert.ToInt32 ("120.5")) / / the input string is not in the correct format. } catch (Exception e) {Console.WriteLine (e.Message);} 14. Comparison of strings:
1. Compare () is the static version of CompareTo (), which returns a string that is less than, greater than, or equal to the latter (- 1, respectively).
String str1 = "you are very happen!"; string str2 = "I am very happen!"; Console.WriteLine (string.Compare (str1, str2)); / / 1Console.WriteLine (str1.CompareTo (str2)); / / 1
2. CompareOrdinal (): compare two strings, regardless of localized language and culture. Divide the entire string into groups of 5 characters (10 bytes), compare them one by one, find the first different ASCII code and exit the loop. And find out the difference between the two ASCII codes.
String str1 = "you are very happen!"; string str2 = "I am very happen!"; Console.WriteLine (string.CompareOrdinal (str1, str2)); / / 48
3. Equals () is equivalent to "= =", static or instance Equals, return equal or unequal (true/false).
String str2 = "I am very happen!"; string str3 = "I am very happen!"; Console.WriteLine (str2.Equals (str3)); / / TrueConsole.WriteLine (str2 = = str3); / / True15, copy of string
(1), String.Copy (str): the parameter str is the string to be copied, and it returns a string equal to the string
(2), SreStr.CopyTo (StartOfSreStr, DestStr, StartOfDestStr, CopyLen): it must be called by the string instance to be copied, and it can copy a part of it to the specified location of the target string.
String s = "Hello World"; string S1 = String.Copy (s); Console.WriteLine (S1); / / Hello Worldchar [] S2 = new char [20]; s.CopyTo (2, S2, 0, 8); Console.WriteLine (S2); / / llo Worl00000000000000000000000016, determine whether a string has started or ended string s = "Hello World"; Console.WriteLine (s.StartsWith ("He")); / / TrueConsole.WriteLine (s.EndsWith ("He")) / / False17, determine whether the character is null or empty, and the return value is bool String s = "Hello World"; string S2 = null;Console.WriteLine (string.IsNullOrEmpty (s)); / / False Console.WriteLine (string.IsNullOrEmpty (S2)); / / True II, char character. 1. The representation of Char:
Literally: char axioms x'
Hexadecimal method: char asides'\ x0058'
Show converted integers: char a = (char) 88
Unicode form: char aversion'\ u0058'
2. Escape characters:
\ n =\ u000a newline character
\ t =\ u0009 tab character
\ r =\ u000d carriage return
\ "=\ u0022 double quotes
\ u0027 single quotation marks
\ u005c backslash
\ b =\ u0008 backspace character
3. Static method of char:
Char.IsDigit (): whether it is a decimal number
Char.IsNumber (): number
Char.IsLetter (): letter
Char.IsLetterOrdigt (): letters or arrays
Char.IsUpper () / IsLower (): upper and lowercase letters
Char.IsPunctuation (): punctuation
Char.IsSymbol (): symbol character
Char.IsControl (): control character
Char.IsSeprator (): delimiter
Char.IsWhiteSpace (): White space character
Char.GetNumberialValue (): get a numeric value
Char.ToUpper () / ToLower (): change case
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