C# VII: 统计文本行数

本文基于StackOverflow的以下问题收集整理而成。
What is the fastest waty to count newlines in a large .NET string: http://stackoverflow.com/questions/2557002/what-is-the-fastest-way-to-count-newlines-in-a-large-net-string
How to count lines in a string: http://stackoverflow.com/questions/11189331/how-to-count-lines-in-a-string

方法一

private static int Count1(string s)
{
    int len = s.Length;
    int c = 0;
    for (int i=0; i < len;  i++)
    {
        if (s[i] == '\n') c++;
    }
    return c+1;
}

方法二

private static int Count2(string s)
{
    int count = -1;
    int index = -1;

    do
    {
        count++;
        index = s.IndexOf('\n', index + 1);
    }
    while (index != -1);

    return count+1;
}

方法三

private static int Count3(string s)
{
    return s.Count( c => c == '\n' ) + 1;
}

方法四

private static int Count4(string s)
{
    int n = 0;
    foreach( var c in s )
    {
        if ( c == '\n' ) n++;
    }
    return n+1;
}

方法五

private static int Count5(string s)
{
    var a = s.ToCharArray();
    int c = 0;
    for (int i=0; i < a.Length; i++)
    {
        if (a[i]=='\n') c++;
    }
    return c+1;
}

性能测试结果显示，最快到最慢为：方法四，方法二，方法一，方法五和方法二。方法二不仅最慢，而且差了1个数量级。

方法六

int numLines = aDiff.text.Length - aDiff.text.Replace(Environment.NewLine, string.Empty).Length;

方法七

int numLines = aDiff.text.Split('\n').Length;

是为之记。
Alva Chien
2016.9.5