C# String.Contains()用法及代码示例

#C# String.Contains()用法及代码示例| 来源: 网络整理| 查看: 265

在C#中，String.Contains()是字符串方法。此方法用于检查子字符串是否出现在给定的字符串内。

用法:

public bool Contains(string str)

参数：

str:这是要检查的字符串。此参数的类型为System.String。

返回值：它返回布尔值。如果子字符串存在于字符串中，或者value是空字符串(“”)，则返回True，否则返回False。

异常：如果str为null，则此方法可以提供ArgumentNullException。

注意：此方法执行区分大小写的检查。搜索将始终从字符串的第一个字符位置开始，一直持续到最后一个字符位置。

以下示例程序旨在说明Contains()方法。

程序1:

// C# program to demonstrate the // String.Contains() Method using System; class Geeks { // Main Method public static void Main() { // string type String str = "GeeksforGeeks"; String substr1 = "for"; String substr2 = "For"; // using String.Contains() Method Console.WriteLine(str.Contains(substr1)); // Here case-sensitive comparison // And substr2 value is 'For' // So its return false Console.WriteLine(str.Contains(substr2)); } } 输出： True False

程序2:使用顺序比较和不区分大小写的顺序比较来确定字符串中是否存在子字符串。

// C# program to illustrate the // String.Contains() Method using // ordinal comparison and case- // insensitive ordinal comparison using System; public static class StringExtensions { // defines a String extension method // which includes a StringComparison parameter public static bool Contains(this String str, String substr, StringComparison cmp) { if (substr == null) throw new ArgumentNullException("substring substring", " cannot be null."); else if (!Enum.IsDefined(typeof(StringComparison), cmp)) throw new ArgumentException("comp is not a member of", "StringComparison, comp"); return str.IndexOf(substr, cmp) >= 0; } } // Driver Class class Geeks { // Main Method public static void Main() { String str = "GeeksforGeeks"; String substr = "FOR"; // For Ordinal StringComparison comp = StringComparison.Ordinal; Console.WriteLine("For {0:G}: {1}", comp, str.Contains(substr, comp)); // for OrdinalIgnoreCase comp = StringComparison.OrdinalIgnoreCase; Console.WriteLine("For {0:G}: {1}", comp, str.Contains(substr, comp)); } } 输出： For Ordinal: False For OrdinalIgnoreCase: True

程序3:下面的示例确定字符串“Computer”是否为给定字符串的子字符串。如果在字符串中找到它，它还将显示其起始位置。

// C# program to demonstrate the // String.Contains() Method // along with the starting position using System; class Example { public static void Main() { string sub1 = "GeeksforGeeks is a Computer Science Portal"; string sub2 = "Computer"; // Check if the substring is // present in the main string bool b = sub1.Contains(sub2); Console.WriteLine("'{0}' is in the string '{1}': {2}", sub2, sub1, b); if (b) { int index = sub1.IndexOf(sub2); if (index >= 0) Console.WriteLine("{0} begins at character position {1}", sub2, index + 1); } } } 输出： 'Computer' is in the string 'GeeksforGeeks is a Computer Science Portal': True Computer begins at character position 20

参考：https://msdn.microsoft.com/en-us/library/system.string.contains

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