1.Compare method

The Compare method has several overloading methods that perform a comparison of two strings according to specified rules and ranges. The method returns an integer describing the relative position in the sorting of the two strings.

String str1 = "czhenya";
String str2 = "Czhenya_CSDN";

//Parameters: String 1, String 2, case sensitive
Console.WriteLine(String.Compare(str1, str2));       //Output: -1
Console.WriteLine(String.Compare(str1, str2, true)); //Output: -1

//Parameters: string 1,str1 start index, string 2,str2 start index, compare length, case sensitive
Console.WriteLine(String.Compare(str1, 0, str2, 0, 7));       //Output: -1
Console.WriteLine(String.Compare(str1, 0, str2, 0, 7, true)); //Output: 0

2.Concat method

Concat methods can be overloaded in a variety of ways to connect to a specified string or object.

  String s1 = "C";
  String s2 = "Zhen";
  String s3 = "Ya";
  String s4 = "_CSDN";
  // This writing supports concatenation of up to four strings
  Console.WriteLine(String.Concat(s1, s2));           //Output: CZhen          
  Console.WriteLine(String.Concat(s1, s2, s3, s4));   //Output: CZhenYa_CSDN
  // There are also three object s that are overloaded with parameter types
  Console.WriteLine(String.Concat(s1, 1, '2', 0.3f)); //Output: C120.3

  // Connection String Array
  String[] strArr = { "A", "BC", "DEF", "GH", "IJKL" };
  Console.WriteLine(String.Concat(strArr));     //Output: ABCDEFGHIJKL

3.Contains method

Returns a bool value indicating whether the specified String object appears in this string.

 String str1 = "Czhenya";
 String str2 = "Czhenya_CSDN";

 // Whether str1 contains str2 (case sensitive) --> or whether str2 is a string of str1
 Console.WriteLine(str1.Contains(str2));     //Output: False
 Console.WriteLine(str2.Contains(str1));     //Output: True
 // Parameter is an overload of type char
 Console.WriteLine(str1.Contains('c'));     //Output: False
 Console.WriteLine(str1.Contains('C'));     //Output: True

4.StartsWith and EndsWith methods

Returns a Boolean value determining whether the start/end of this string instance matches the specified string.

 String str1 = "Czhenya";
 String str2 = "Czhenya_CSDN";
 
 //Does str1 start with str2
 Console.WriteLine(str1.StartsWith(str2));     //Output: False
 Console.WriteLine(str1.StartsWith('C'));      //Output: True

 Console.WriteLine(str2.StartsWith(str1));     //Output: True
 Console.WriteLine(str2.StartsWith('c'));      //Output: False

5.Equals method

The Equals method can be overloaded in a variety of ways to determine whether two String instances have the same value according to certain rules.

 String str1 = "Czhenya";
 String str2 = "czhenya";

 //Parameter is of type object
 Console.WriteLine(str1.Equals(str2));           //Output: False
 // Comparing str1 with str2
 Console.WriteLine(String.Equals(str1,str2));    //Output: False
 // Comparing str1 with str2 is case insensitive
 Console.WriteLine(String.Equals(str1,str2, StringComparison.OrdinalIgnoreCase)); 
 //Output: True

6.ToLower method and ToUpper method

Converts a character in a string to lowercase or to uppercase.

  String str1 = "Czhenya";
  String str2 = "czhenya";
  
  Console.WriteLine(str1.ToLower());    //Output: czhenya
  Console.WriteLine(str2.ToUpper());    //Output: CZHENYA

7.Substring method

Substrings have two overload modes that allow you to Substring a string at a specified starting position and length.

 String str1 = "Czhenya";
 //Parameter: Start Index
 Console.WriteLine(str1.Substring(2));     //Output: henya
 //Parameters: start index, intercept length
 Console.WriteLine(str1.Substring(0, 2));  //Output: Cz

8.Split method

Split, which implements the function of splitting strings into multiple substrings according to specified characters.

    //Use underscore'_"Delimited string
    String str2 = "Czhenya_C_S_D_";
    string[] res2 = str2.Split('_');
    for (int i = 0; i < res2.Length; i++)
    {
          Console.Write(res2[i] + "..."); // Output: Czhenya...C...S...D...
    }
    Console.WriteLine();
    // Default parameters:StringSplitOptions.None: The return value includes an array element containing an empty string.
    // StringSplitOptions.RemoveEmptyEntries: The return value does not include an array element containing an empty string.
    string[] res3 = str2.Split('_', StringSplitOptions.RemoveEmptyEntries);
    for (int i = 0; i < res3.Length; i++)
    {
         Console.Write(res3[i] + "..."); // Output: Czhenya...C...S...D...
    }
    Console.WriteLine();

    //Parameters: Separate characters, separate groups, default parameters:StringSplitOptions.None
    string[] res4 = str2.Split('_',3);
    for (int i = 0; i < res4.Length; i++)
    {
          Console.Write(res4[i] + "..."); // Output: Czhenya...C...S_D_...
    }
    Console.WriteLine();

9.Replace method

The Replace method replaces the character or substring specified in this instance.

   String str1 = "Czhenya_CSDN";
   // Replace the character'C'in the string with the character'A'
   Console.WriteLine(str1.Replace('C','A'));           //Output: Azhenya_ASDN
   // String "ABCD", replacing string "CSDN"
   Console.WriteLine(str1.Replace("CSDN", "ABCD"));    //Output: Czhenya_ABCD

10.Remove method

The Remove method deletes the character specified in this instance.

 String str1 = "Czhenya_CSDN";
 //Parameter: Index to start removing
 Console.WriteLine(str1.Remove(7));           //Output: Czhenya
 //Parameter: Start removing index, remove length
 Console.WriteLine(str1.Remove(0,2));         //Output: henya_CSDN