vb.net - 计算字符串中特定字符的出现次数

Question

计算字符串中特定字符出现次数的最简单方法是什么？

也就是说，我需要编写一个函数，countTheCharacters()，这样

str = "the little red hen"
count = countTheCharacters(str,"e") ' Count should equal 4
count = countTheCharacters(str,"t") ' Count should equal 3

Answer 1

最直接的方法是简单地循环字符串中的字符:

Public Function CountCharacter(ByVal value As String, ByVal ch As Char) As Integer
  Dim cnt As Integer = 0
  For Each c As Char In value
    If c = ch Then 
      cnt += 1
    End If
  Next
  Return cnt
End Function

用法:

count = CountCharacter(str, "e"C)

另一种几乎同样有效且代码较短的方法是使用 LINQ 扩展方法:

Public Function CountCharacter(ByVal value As String, ByVal ch As Char) As Integer
  Return value.Count(Function(c As Char) c = ch)
End Function