C#-計算相對路徑

C#-計算相對路徑

   /**//// <summary>
        /// 計算相對路徑
        /// 後者相對前者的路徑。
        /// </summary>
        /// <param name="mainDir">主目錄</param>
        /// <param name="fullFilePath">檔案的絕對路徑</param>
        /// <returns>fullFilePath相對於mainDir的路徑</returns>
        /// <example>
        /// @"..\..\regedit.exe" = GetRelativePath(@"D:\Windows\Web\Wallpaper\", @"D:\Windows\regedit.exe" );
        /// </example>
        public static string GetRelativePath(string mainDir, string fullFilePath)
        {
            if (!mainDir.EndsWith("\\"))
            {
                mainDir += "\\"; 
            }

            int intIndex = -1, intPos = mainDir.IndexOf('\\');
          
            while (intPos >= 0)
            {
                intPos++;
                if (string.Compare(mainDir, 0, fullFilePath, 0, intPos, true) != 0) break;
                intIndex = intPos;
                intPos = mainDir.IndexOf('\\', intPos);
            }

              if (intIndex >= 0)
            {
                fullFilePath = fullFilePath.Substring(intIndex);
                intPos = mainDir.IndexOf("\\", intIndex);
                while (intPos >= 0)
                {
                    fullFilePath = "..\\" + fullFilePath;
                    intPos = mainDir.IndexOf("\\", intPos + 1);
                }
            }
           
            return fullFilePath;
        }