如何对某个词在字符串中出现的次数进行计数 (LINQ) (C#)
此示例演示如何使用 LINQ 查询对指定词在字符串中出现的次数进行计数。 请注意，若要执行计数，首先需调用 Split 方法来创建词数组。 Split 方法存在性能开销。 如果只需要统计字符串的字数，则应考虑改用 Matches 或 IndexOf 方法。 但是，如果性能不是关键问题，或者已拆分句子以对其执行其他类型的查询，则使用 LINQ 来计数词或短语同样有意义。
示例
class CountWords
{
static void Main()
{
string text = @"Historically, the world of data and the world of objects" +
@" have not been well integrated. Programmers work in C# or Visual Basic" +
@" and also in SQL or XQuery. On the one side are concepts such as classes," +
@" objects, fields, inheritance, and .NET APIs. On the other side" +
@" are tables, columns, rows, nodes, and separate languages for dealing with" +
@" them. Data types often require translation between the two worlds; there are" +
@" different standard functions. Because the object world has no notion of query, a" +
@" query can only be represented as a string without compile-time type checking or" +
@" IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to" +
@" objects in memory is often tedious and error-prone.";
string searchTerm = "data";
//Convert the string into an array of words
string[] source = text.Split(new char[] { '.', '?', '!', ' ', ';', ':', ',' }, StringSplitOptions.RemoveEmptyEntries);
// Create the query. Use the InvariantCultureIgnoreCase comparision to match "data" and "Data"
var matchQuery = from word in source
where word.Equals(searchTerm, StringComparison.InvariantCultureIgnoreCase)
select word;
// Count the matches, which executes the query.
int wordCount = matchQuery.Count();
Console.WriteLine("{0} occurrences(s) of the search term \"{1}\" were found.", wordCount, searchTerm);
// Keep console window open in debug mode
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
}
/* Output:
3 occurrences(s) of the search term "data" were found.
*/
编译代码
使用 System.Linq 和 System.IO 命名空间的 using 指令创建 C# 控制台应用程序项目。