StringBuilder-查找字符的最后一个索引

Question

我想在中找到特定的最后一个字符StringBuilder。
我知道，可以解决此问题，while()但是是否有构建它的选项可以轻松实现？

例如：

private static StringBuilder mySb = new StringBuilder("");
mySb.Add("This is a test[n] I like Orange juice[n] Can you give me some?");

现在：应该找到]并给我所有权。喜欢：40

提前致谢

Answer 1

由于没有内置方法，因此始终string无法StringBuilder通过过孔创建通孔，ToString因此您可以为此创建扩展方法：

public static int LastIndexOf(this StringBuilder sb, char find, bool ignoreCase = false, int startIndex = -1, CultureInfo culture = null)
{
    if (sb == null) throw new ArgumentNullException(nameof(sb));
    if (startIndex == -1) startIndex = sb.Length - 1;
    if (startIndex < 0 || startIndex >= sb.Length) throw new ArgumentException("startIndex must be between 0 and sb.Lengh-1", nameof(sb));
    if (culture == null) culture = CultureInfo.InvariantCulture;

    int lastIndex = -1;
    if (ignoreCase) find = Char.ToUpper(find, culture);
    for (int i = startIndex; i >= 0; i--)
    {
        char c = ignoreCase ? Char.ToUpper(sb[i], culture) : (sb[i]);
        if (find == c)
        {
            lastIndex = i;
            break;
        }
    }
    return lastIndex;
}

将其添加到静态的，可访问的（扩展）类中，然后可以通过以下方式使用它：

StringBuilder mySb = new StringBuilder("");
mySb.Append("This is a test[n] I like Orange juice[n] Can you give me some?");
int lastIndex = mySb.LastIndexOf(']');  // 39