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C# code examples: System.String

Object construction

using System; public class Program { public static void Main(string[] args) { String v = "Hello!"; Console.WriteLine("v.toString() = \"{0}\"", v); Console.ReadKey(); } }

Accessing the characters of a string as array elements

using System; public class Program { public static void Main() { string s = "Hallo"; for (int i = 0; i < s.Length; i++) { Console.WriteLine(s[i]); } Console.ReadKey(); } }

Any()

using System; using System.Linq; public class Program { public static void Main() { string[] a = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" }; Console.WriteLine("The array a {0} elements.", a.Any() ? "contains" : "does not contain"); string[] b = new String[0]; Console.WriteLine("The array b {0} elements.", b.Any() ? "contains" : "does not contain"); Console.ReadKey(); } }

Any(System.String => System.Boolean)

using System; using System.Linq; public class Program { public static void Main() { string[] a = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" }; Console.WriteLine("The array {0} elements with the letter '{1}'.", a.Any(day => day.Contains('u')) ? "contains" : "does not contain", 'u'); Console.WriteLine("The array {0} elements with the letter '{1}'.", a.Any(day => day.Contains('x')) ? "contains" : "does not contain", 'x'); Console.ReadKey(); } }

Average(System.String => System.Int32)

using System; using System.Linq; public class Program { public static void Main() { string[] a = { "5", "3", "-6", "12" }; double average = a.Average(s => Convert.ToInt32(s)); Console.WriteLine("The average number is {0}.", average); Console.ReadKey(); } }

Compare(System.String, System.String)

using System; public class Program { public static void Main() { string s1 = "one"; string s2 = "two"; Console.WriteLine(String.Compare(s1, s2)); Console.WriteLine(String.Compare(s2, s1)); Console.WriteLine(String.Compare(s1, s1)); Console.ReadKey(); } }

Compare(System.String, System.String, System.Boolean)

using System; public class Program { public static void Main() { string s1 = "hello"; string s2 = "HELLO"; Console.WriteLine("Case sensitive comparison: {0}", String.Compare(s1, s2, false)); Console.WriteLine("Case sensitive comparison: {0}", String.Compare(s2, s1, false)); Console.WriteLine("Case insensitive comparison: {0}", String.Compare(s1, s2, true)); Console.ReadKey(); } }

Compare(System.String, System.String, System.StringComparison)

using System; using System.Globalization; using System.Threading; public class Program { public static void Main() { string s1 = "å"; string s2 = "z"; Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US"); Console.WriteLine("Current culture = {0}\n", Thread.CurrentThread.CurrentCulture.EnglishName); Console.WriteLine("{0}\n", String.Compare(s1, s2, StringComparison.CurrentCulture)); Thread.CurrentThread.CurrentCulture = new CultureInfo("sv-SE"); Console.WriteLine("Current culture = {0}\n", Thread.CurrentThread.CurrentCulture.EnglishName); Console.WriteLine(String.Compare(s1, s2, StringComparison.CurrentCulture)); Console.ReadKey(); } }

Compare(System.String, System.String, System.Boolean, System.Globalization.SystemInfo)

using System; using System.Globalization; public class Program { public static void Main() { string s1 = "å"; string s2 = "z"; Console.WriteLine("American case sensitive comparison: {0}", String.Compare(s1, s2, false, new CultureInfo("en-US"))); Console.WriteLine("Swedish case sensitive comparison: {0}\n", String.Compare(s1, s2, false, new CultureInfo("sv-SE"))); s1 = "a"; s2 = "A"; Console.WriteLine("American case insensitive comparison: {0}", String.Compare(s1, s2, true, new CultureInfo("en-US"))); Console.WriteLine("Swedish case insensitive comparison: {0}", String.Compare(s1, s2, true, new CultureInfo("sv-SE"))); Console.ReadKey(); } }

CompareOrdinal(System.String, System.String)

using System; public class Program { public static void Main() { Console.WriteLine(String.CompareOrdinal("5", "6")); Console.WriteLine(String.CompareOrdinal("6", "5")); Console.WriteLine(String.CompareOrdinal("5", "5")); Console.ReadKey(); } }

CompareOrdinal(System.String, System.Int32, System.String, System.Int32, System.Int32)

using System; public class Program { public static void Main() { Console.WriteLine(String.CompareOrdinal("NOP5", 3, "A6", 1, 1)); Console.WriteLine(String.CompareOrdinal("A6", 1, "NOP5", 3, 1)); Console.WriteLine(String.CompareOrdinal("NOP5", 3, "Q5", 1, 1)); Console.ReadKey(); } }

CompareTo(System.String)

using System; public class Program { public static void Main() { string s1 = "one"; string s2 = "two"; Console.WriteLine(s1.CompareTo(s2)); Console.WriteLine(s2.CompareTo(s1)); Console.WriteLine(s1.CompareTo(s1)); Console.ReadKey(); } }

CompareTo(System.Object)

using System; public class Program { public static void Main() { string s = "hello"; Object o = new Object(); o = "goodbye"; // o is a string, so it is okay to use CompareTo(). Console.WriteLine(s.CompareTo(o)); o = new DateTime(); // o is not a string anymore. try { Console.WriteLine(s.CompareTo(o)); } catch (Exception ex) { Console.WriteLine(ex.Message); } Console.ReadKey(); } }

Concat(System.String, System.String)

using System; public class Program { public static void Main() { Console.WriteLine(String.Concat("Hello ", "world.")); Console.ReadKey(); } }

Concat(System.String[])

using System; public class Program { public static void Main(string[] args) { string[] a = { "Hello", ", ", "world", "!" }; Console.WriteLine(String.Concat(a)); Console.ReadKey(); } }

Contains(System.String)

using System; public class Program { public static void Main() { string s = "Hello world"; Console.WriteLine(@"The string ""{0}"" {1} the string ""{2}"".", s, s.Contains("lo") ? "contains" : "does not contain", "lo"); Console.WriteLine(@"The string ""{0}"" {1} the string ""{2}"".", s, s.Contains("ro") ? "contains" : "does not contain", "ro"); Console.ReadKey(); } }

Copy(System.String)

using System; class Program { static void Main() { string s1 = "Hello"; string s2 = String.Empty; s2 = s1; // Show that s1 and s2 refer to the same object Console.WriteLine(Object.ReferenceEquals(s1, s2)); s2 = String.Copy(s1); // Show that s1 and s2 now still represent the same string. Console.WriteLine("{0} = {1}", s1, s2); // But they do NOT refer to the same object anymore. Console.WriteLine(Object.ReferenceEquals(s1, s2)); Console.ReadKey(); } }

CopyTo(System.Int32, System.Char[], System.Int32, System.Int32)

using System; public class Program { public static void Main() { char[] c = { 'h', 'e', 'l', 'l', 'o' }; Console.WriteLine(c); string s = "chamber"; s.CopyTo(2, c, 1, 1); // Replace the 'e' in c[] by the 'a' in s. Console.WriteLine(c); Console.ReadKey(); } }

Count()

using System; using System.Linq; public class Program { public static void Main() { string[] a = { "alpha", "beta", "gamma" }; Console.WriteLine(a.Count()); Console.ReadKey(); } }

DefaultIfEmpty()

using System; using System.Linq; class Program { static void Main() { string[] nameList1 = { "Steve", "Andy", "George" }; string[] nameList2 = new string[0]; // Empty foreach (string name in nameList1.DefaultIfEmpty()) { Console.WriteLine("name: {0}", name); } Console.WriteLine(); // nameList2 is empty, so the default for the type (an empty string) will be displayed. foreach (string name in nameList2.DefaultIfEmpty()) { Console.WriteLine("name: {0}", name); } Console.ReadKey(); } }

DefaultIfEmpty(System.String)

using System; using System.Linq; class Program { static void Main() { string defaultName = "John"; string[] nameList1 = { "Steve", "Andy", "George" }; string[] nameList2 = new string[0]; // Empty foreach (string name in nameList1.DefaultIfEmpty(defaultName)) { Console.WriteLine(name); } Console.WriteLine(); // nameList2 is empty, so now the default name will be displayed. foreach (string name in nameList2.DefaultIfEmpty(defaultName)) { Console.WriteLine(name); } Console.ReadKey(); } }

Count(System.String => System.Boolean)

using System; using System.Linq; public class Program { public static void Main() { string[] a = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" }; Console.WriteLine("{0} of the names of days contain the letter '{1}'.", a.Count(day => day.Contains('u')), 'u'); Console.ReadKey(); } }

Distinct()

using System; using System.Linq; public class Program { public static void Main() { string[] s = { "oak", "beech", "maple", "oak", "maple", "pine" }; foreach (string tree in s.Distinct()) { Console.WriteLine(tree); } Console.ReadKey(); } }

Empty

using System; class Program { static void Main(string[] args) { string s = "hello"; Console.WriteLine("The length of s is {0} characters.", s.Length); s = String.Empty; Console.WriteLine("The length of s is now {0} characters.", s.Length); Console.ReadKey(); } }

EndsWith(System.String)

using System; class Program { static void Main(string[] args) { string s = "Hello"; if (s.EndsWith("lo")) { Console.WriteLine(@"""{0}"" ends with ""lo"".", s); } s = "Goodbye"; if (!s.EndsWith("lo")) { Console.WriteLine(@"""{0}"" does not end with ""lo"".", s); } Console.ReadKey(); } }

First()

using System; using System.Linq; public class Program { public static void Main() { string[] a = { "alpha", "beta", "gamma" }; Console.WriteLine(a.Last()); Console.ReadKey(); } }

First(System.String => System.Boolean)

using System; using System.Linq; public class Program { public static void Main() { string[] trees = { "horse-chestnut", "Norway maple", "Scotch pine", "field maple" }; string firstMaple = trees.First(name => name.Contains("maple")); Console.WriteLine("The first maple in the list is the {0}.", firstMaple); Console.ReadKey(); } }

Format(System.String, System.Object)

using System; public class Program { public static void Main() { Console.WriteLine(String.Format("{0:x4}", 301)); Console.ReadKey(); } }

IndexOf(System.Char)

using System; class Program { static void Main(string[] args) { string s = "Hello"; Console.WriteLine(@"The first occurrence of the character 'l' in ""{0}"" was found at position {1}.", s, s.IndexOf('l')); Console.ReadKey(); } }

IndexOf(System.Char, System.Int32)

using System; class Program { static void Main(string[] args) { string s = "Hello"; int p = s.IndexOf('l') + 1; Console.WriteLine(@"The second occurrence of the character 'l' in ""{0}"" was found at position {1}.", s, s.IndexOf('l', p)); Console.ReadKey(); } }

IndexOf(System.String)

using System; class Program { static void Main(string[] args) { string s = "Hello love"; Console.WriteLine(@"The first occurrence of the substring ""lo"" in ""{0}"" was found at position {1}.", s, s.IndexOf("lo")); Console.ReadKey(); } }

IndexOf(System.String, System.Int32)

using System; class Program { static void Main(string[] args) { string s = "Hello love"; int p = s.IndexOf("lo") + 1; Console.WriteLine(@"The second occurrence of the substring ""lo"" in ""{0}"" was found at position {1}.", s, s.IndexOf("lo", p)); Console.ReadKey(); } }

Intern(System.String)

using System; using System.Text; public class Program { public static void Main() { string s1 = "hello"; string s2 = String.Intern(s1); // Value of s1 in pool. s1 and s2 refer to the same object. string s3 = new StringBuilder().Append("hel").Append("lo").ToString(); string s4 = String.Intern(s3); // Value of s3 not in pool. New string created. s3 and s4 refer to different objects. Console.WriteLine("s1 = {0}", s1); Console.WriteLine("s2 = {0}", s2); Console.WriteLine("s3 = {0}", s3); Console.WriteLine("s4 = {0}", s4); Console.WriteLine("(Object)s1 {0} (Object)s2", (Object)s1 == (Object)s2 ? "==" : "!="); Console.WriteLine("(Object)s1 {0} (Object)s3", (Object)s1 == (Object)s3 ? "==" : "!="); Console.WriteLine("(Object)s1 {0} (Object)s4", (Object)s1 == (Object)s4 ? "==" : "!="); Console.WriteLine("(Object)s3 {0} (Object)s4", (Object)s3 == (Object)s4 ? "==" : "!="); Console.ReadKey(); } }

Insert(System.Int32, System.String)

using System; public class Program { public static void Main() { string s = "012345"; Console.WriteLine(s.Insert(3, "-")); Console.ReadKey(); }

IsInterned(System.String)

using System; using System.Text; public class Program { public static void Main() { string s1 = "hello"; string s2 = new StringBuilder().Append("hel").Append("lo").ToString(); string s3 = new StringBuilder().Append("goodbye").Append("bye").ToString(); Console.WriteLine("String s1 is {0}.", String.IsInterned(s1) != null ? "interned" : "not interned"); Console.WriteLine("String s2 is {0}.", String.IsInterned(s2) != null ? "interned" : "not interned"); Console.WriteLine("String s3 is {0}.", String.IsInterned(s3) != null ? "interned" : "not interned"); Console.ReadKey(); } }

IsNullOrEmpty(System.String)

using System; class Program { static void Main(string[] args) { string s = String.Empty; if (String.IsNullOrEmpty(s)) { Console.WriteLine("The string s is empty or null."); } s = null; if (String.IsNullOrEmpty(s)) { Console.WriteLine("The string s is still empty or null."); } s = "xyz"; if (!String.IsNullOrEmpty(s)) { Console.WriteLine("The string s is not empty or null anymore."); } s = "xyz"; Console.ReadKey(); } }

Join(System.String, System.String)

using System; public class Program { public static void Main() { string[] a = { "alpha", "beta", "gamma", "delta", "epsilon" }; Console.WriteLine(String.Join(";", a)); Console.ReadKey(); } }

Join(System.String, System.String, System.Int32, System.Int32)

using System; public class Program { public static void Main() { string[] a = { "alpha", "beta", "gamma", "delta", "epsilon" }; Console.WriteLine(String.Join(";", a, 1, 2)); Console.ReadKey(); } }

Last()

using System; using System.Linq; public class Program { public static void Main() { string[] a = { "alpha", "beta", "gamma" }; Console.WriteLine(a.Last()); Console.ReadKey(); } }

Last(System.String => System.Boolean)

using System; using System.Linq; public class Program { public static void Main() { string[] trees = { "Norway maple", "Scotch pine", "field maple", "horse-chestnut" }; string lastMaple = trees.Last(name => name.Contains("maple")); Console.WriteLine("The last maple in the list is the {0}.", lastMaple); Console.ReadKey(); } }

Length

using System; class Program { static void Main(string[] args) { string s = "hello"; Console.WriteLine(@"The length of ""{0}"" is {1} characters.", s, s.Length); Console.ReadKey(); } }

OrderBy(System.String => System.String)

using System; using System.Linq; public class Program { public static void Main() { string[] a = { "alpha", "beta", "gamma", "delta" }; foreach (string greekLetterName in a.OrderBy(x => x)) { Console.WriteLine(greekLetterName); } Console.ReadKey(); } }

OrderByDescending(System.String => System.String)

using System; using System.Linq; public class Program { public static void Main() { string[] a = { "alpha", "beta", "gamma", "delta" }; foreach (string greekLetterName in a.OrderByDescending(x => x)) { Console.WriteLine(greekLetterName); } Console.ReadKey(); } }

PadLeft(System.Int32)

using System; public class Program { public static void Main() { string s = "hello"; Console.WriteLine("*" + s.PadLeft(10) + "*"); Console.ReadKey(); } }

PadLeft(System.Int32, System.Char)

using System; public class Program { public static void Main() { string s = "hello"; Console.WriteLine("*" + s.PadLeft(10) + "*"); Console.ReadKey(); } }

PadRight(System.Int32)

using System; public class Program { public static void Main() { string s = "hello"; Console.WriteLine("*" + s.PadRight(10) + "*"); Console.ReadKey(); } }

PadRight(System.Int32, System.Char)

using System; public class Program { public static void Main() { string s = "hello"; Console.WriteLine(s.PadRight(10, '*')); Console.ReadKey(); } }

StartsWith(System.String)

using System; class Program { static void Main(string[] args) { string s = "Hello"; if (s.StartsWith("Hel")) { Console.WriteLine(@"""{0}"" starts with ""Hel"".", s); } s = "Goodbye"; if (!s.StartsWith("Hel")) { Console.WriteLine(@"""{0}"" does not start with ""Hel"".", s); } Console.ReadKey(); } }

Trim()

using System; class Program { static void Main(string[] args) { string s = " The leading and trailing spaces have been removed. "; Console.WriteLine("*{0}*", s.Trim()); Console.ReadKey(); } }

Trim(System.Chars[])

using System; class Program { static void Main(string[] args) { char[] a = {' ', '!'}; string s = " All leading spaces and trailing exclamation marks have been removed!!!"; Console.WriteLine("*{0}*", s.Trim(a)); Console.ReadKey(); } }

TrimEnd(System.Chars[])

using System; class Program { static void Main(string[] args) { char[] a = {'!'}; string s = "All trailing exclamation marks have been removed!!!"; Console.WriteLine(s.TrimEnd(a)); Console.ReadKey(); } }

TrimStart(System.Chars[])

using System; class Program { static void Main(string[] args) { char[] a = {'!'}; string s = "!!!All leading exclamation marks have been removed!"; Console.WriteLine(s.TrimStart(a)); Console.ReadKey(); } }