C# Json格式化换行输出

public static string JsonBeauty(this string input, bool arrayWrap = false, string indents = "   ") {
    void AppendIndent(StringBuilder sb, int count, string indents) { for (; count > 0; --count) sb.Append(indents); }
    var output = new StringBuilder();
    int depth = 0;
    for (int i = 0; i < input.Length; ++i) {
        char ch = input[i];
        if (ch == '\"') {
            bool str = true;
            while (str) {
                output.Append(ch);
                ch = input[++i];
                if (ch == '\\') { output.Append(ch); ch = input[++i]; } 
                else if (ch == '\"') str = false;
            }
        }
        switch (ch) {
            case '{': output.Append(ch); output.AppendLine(); AppendIndent(output, ++depth, indents); break;
            case '[': output.Append(ch); if (arrayWrap) { output.AppendLine(); AppendIndent(output, ++depth, indents); } break;
            case '}': output.AppendLine(); AppendIndent(output, --depth, indents); output.Append(ch); break;
            case ']': if (arrayWrap) { output.AppendLine(); AppendIndent(output, --depth, indents); } output.Append(ch); break;
            case ',': output.Append(ch); output.AppendLine(); AppendIndent(output, depth, indents); break;
            case ':': output.Append(" : "); break;
            default: if (!char.IsWhiteSpace(ch)) output.Append(ch); break;
        }
    }
    return output.ToString();
}

从FastJson提取出来的，