为什么StringBuilder没有IndexOf方法？

I understand that I can call ToString().IndexOf(...), but I don't want to create an extra string. I understand that I can write a search routine manually. I just wonder why such a routine doesn't already exist in the framework.

我知道我可以调用ToString（）。IndexOf（...），但我不想创建额外的字符串。我知道我可以手动编写搜索例程。我只是想知道为什么框架中不存在这样的例程。

3 个解决方案

#1

Unfortunately, many of the methods implemented for String could have been implemented for StringBuilder but that was not done. Consider using extension methods to add what you care about.

不幸的是，为String实现的许多方法都可以为StringBuilder实现，但是没有完成。考虑使用扩展方法添加您关心的内容。

#2

I know this is an old question, however I have written a extension method that performs an IndexOf on a StringBuilder. It is below. I hope it helps anyone that finds this question, either from a Google search or searching *.

我知道这是一个老问题，但是我编写了一个在StringBuilder上执行IndexOf的扩展方法。它在下面。我希望通过Google搜索或搜索*帮助任何人找到这个问题。

/// <summary>
/// Returns the index of the start of the contents in a StringBuilder
/// </summary>        
/// <param name="value">The string to find</param>
/// <param name="startIndex">The starting index.</param>
/// <param name="ignoreCase">if set to <c>true</c> it will ignore case</param>
/// <returns></returns>
public static int IndexOf(this StringBuilder sb, string value, int startIndex, bool ignoreCase)
{            
    int index;
    int length = value.Length;
    int maxSearchLength = (sb.Length - length) + 1;

    if (ignoreCase)
    {
        for (int i = startIndex; i < maxSearchLength; ++i)
        {
            if (Char.ToLower(sb[i]) == Char.ToLower(value[0]))
            {
                index = 1;
                while ((index < length) && (Char.ToLower(sb[i + index]) == Char.ToLower(value[index])))
                    ++index;

                if (index == length)
                    return i;
            }
        }

        return -1;
    }

    for (int i = startIndex; i < maxSearchLength; ++i)
    {
        if (sb[i] == value[0])
        {
            index = 1;
            while ((index < length) && (sb[i + index] == value[index]))
                ++index;

            if (index == length)
                return i;
        }
    }

    return -1;
}

#3

Calling ToString() on a StringBuilder doesn't create an extra object, confusingly. Internally, StringBuilder stores a String object, for performance; calling ToString() simply returns that object.

在StringBuilder上调用ToString（）不会造成额外的对象，令人困惑。在内部，StringBuilder存储一个String对象，以提高性能;调用ToString（）只返回该对象。

#1