並行程式的一點注意事項

    這幾天無事,把自己以前寫的一套CMS程式拿來改改,想用parallel.foreach來提高產生HTML的效率

    模版解析類就沒動,直接把以前的for迴圈改成parallel.foreach,就出現了未將對象引用設定到對象執行個體的錯誤,尋找了半天,才發現問題出現在模版解析類的載入模版裡

 

代碼

public void Load()
        {
try
            {
string CacheKey = "cache_" + tempPath;
object objModel = CacheHelper.GetCache(CacheKey);
if (objModel == null)
                {
using (StreamReader sr = new StreamReader(HttpContext.Current.Server.MapPath(tempPath))
                    {
                        tempContext = sr.ReadToEnd();
                        CacheDependency dep = new CacheDependency(HttpContext.Current.Server.MapPath(tempPath), DateTime.Now);
                        CacheHelper.SetCache(CacheKey, tempContext as object, dep, DateTime.Now.AddMinutes(30), TimeSpan.Zero);
                    }
                }
            }
catch (UserException ex)
            {
throw new UserException(ex.ToString());
            }
        }

 

在多線程裡面使用HttpContext.Current,HttpContext.Current得到是null.

 

 

StreamReader sr = new StreamReader(HttpContext.Current.Server.MapPath(tempPath))
//修改成下面就行
StreamReader sr = new StreamReader(System.AppDomain.CurrentDomain.BaseDirectory.ToString() + tempPath)

 

另在附上一個DZ裡的解決辦法

代碼

public static string MapPath(string strPath)

{
if (HttpContext.Current != null)
  {
return HttpContext.Current.Server.MapPath(strPath);
  }
else //非web程式引用
  {
  strPath = strPath.Replace("/", "\\");
if (strPath.StartsWith("\\"))
  {
//strPath = strPath.Substring(strPath.IndexOf('\\', 1)).TrimStart('\\');
  strPath = strPath.TrimStart('\\');
  }
return System.IO.Path.Combine(AppDomain.CurrentDomain.BaseDirectory, strPath);
  }
  }