自定义Func方法支持out，ref参数

默认的Func不支持Out，ref类型的参数，所以需要自定义个delegate func来满足需求。具体代码如下

public delegate TResult FuncEX<T1, T2, T3, T4, T5, out TResult>(T1 obj1, T2 obj2, out T3 obj3, out T4 obj4, ref T5 obj5);
    public void ContractFileDownload_DownloadPurOrder()
    {
        decimal seqID = Request["ID"].ExToDecimal();
        decimal supplierID = Request["SupplierID"].ExToDecimal();

        string msg = "";
        string fileUrl, filePath;
       HttpContext MainthreadContext = HttpContext.Current;
        FuncEX<decimal, decimal, string, string, HttpContext, string> dl = PurOrder;
        dl.BeginInvoke(seqID, supplierID, out fileUrl, out filePath, ref MainthreadContext, TakesAWhileCompleted, dl);

    }

    public string PurOrder(decimal seqID, decimal supplierID, out string fileUrl, out string filePath,ref HttpContext context)
    {
        using (var bllProvider = BLLProviders.Create())
        {
            return bllProvider.Cas_invest_contractBLL.downLoad_PurOrder(seqID, supplierID, out fileUrl, out filePath,ref context);
        }
    }

    public void TakesAWhileCompleted(IAsyncResult ar)
    {
        if (ar != null)
        {
            string fileUrl, filePath;
            HttpContext currentContext=null;
            FuncEX<decimal, decimal, string, string, HttpContext, string> dl = (FuncEX<decimal, decimal, string, string, HttpContext, string>)ar.AsyncState;
            string msg = dl.EndInvoke(out fileUrl, out filePath, ref currentContext, ar);

        }
    }