vb.net – 计算字符串中特定字符的出现次数

计算字符串中特定字符出现次数的最简单方法是什么？

即我需要写一个函数countTheCharacters()

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

最直接的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
  Next
  Return cnt
End Function

用法：

count = CountCharacter(str,"e"C)

另一种几乎同样有效并且给出较短代码的方法是使用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