扫描指定文件夹下是否存在某一文件

通过递归法遍历文件目录，判断指定文件是否存在的一个函数，可以设定遍历目录层数.

 /**/       /// <summary>
        /// 扫描指定文件夹下是否存在某一文件
        /// </summary>
        /// <param name="filename">文件名</param>
        /// <param name="path">路径</param>
        /// <param name="depth">扫描目录层数,0表示不限制层数</param>
        /// <returns>true/false</returns>
        public static bool FileExist(string filename, string path, int depth)
        ...{
            if (depth < 0) throw new Exception("depth must >=0");
            try
            ...{
                DirectoryInfo mainDir;
                mainDir = new DirectoryInfo(path);
                //遍历文件
                foreach (FileInfo f in mainDir.GetFiles())
                ...{
                    //增加文件
                    if (filename.ToLower() == f.Name.ToLower())
                    ...{
                        return true;
                    }
                }
                //遍历文件目录
                if (depth == 0)
                ...{
                    foreach (DirectoryInfo d in mainDir.GetDirectories())
                    ...{
                        //递归调用
                        if (FileExist(filename, Path.Combine(path, d.Name), 0))
                            return true;
                    }
                }
                else if (depth == 1)
                ...{
                }
                else
                ...{
                    foreach (DirectoryInfo d in mainDir.GetDirectories())
                    ...{
                        //递归调用
                        if (FileExist(filename, Path.Combine(path, d.Name), depth - 1))
                            return true;
                    }
                }
                return false;
            }
            catch (Exception)
            ...{
                return false;
            }
        }