使用ASP.NET MVC中的SSRS以excel格式下载报告

Question

在我的一个项目中，我使用SSRS生成Excel和PDF格式的报告。当我通过visual studio运行应用程序时，一切正常。但是当应用程序托管在服务器上时，它会给我随机错误，并显示以下错误消息：

Microsoft.ReportingServices.ReportProcessing.ReportProcessingException: Failed to load expression host assembly. Details: Object reference not set to an instance of an object.

以下是生成报告的代码：

Function Export(model As AshDailyReportModel) As ActionResult
        If ModelState.IsValid Then
            Try
                Dim Result As New List(Of AshDailyConsolidatedReportModel)
                Result = ReportBL.Instance.GetData_ASHDailyConsolidatedReport(model)
                If (Result.Count > 0) Then
                    Dim localReport As LocalReport = New LocalReport
                    localReport.ReportPath = StringUtility.AshDailyConsolidateReportPath
                    Dim reportDataSource As ReportDataSource = New ReportDataSource(StringUtility.dsAshDailyConsolidateReport, Result)
                    localReport.DataSources.Add(reportDataSource)
                    If (model.ExportType = DBEnum.ExportType.Excel) Then
                        Dim bytes() As Byte
                        Try
                            Dim warnings As Warning() = Nothing
                            Dim streamids As String() = Nothing
                            Dim mimeType As String = Nothing
                            Dim encoding As String = Nothing
                            Dim extension As String = Nothing
                            ' Setup the report viewer object and get the array of bytes
                            Dim viewer As New ReportViewer()
                            viewer.ProcessingMode = ProcessingMode.Local
                            viewer.LocalReport.ReportPath = StringUtility.AshDailyConsolidateReportPath

                            viewer.LocalReport.SetBasePermissionsForSandboxAppDomain(New System.Security.PermissionSet(System.Security.Permissions.PermissionState.Unrestricted))
                            viewer.LocalReport.DataSources.Add(reportDataSource)
                            bytes = viewer.LocalReport.Render("Excel", Nothing, mimeType, encoding, extension, streamids, warnings)

                            Response.Buffer = True
                            Response.Clear()
                            Response.ContentType = StringUtility.ApplicationExcel
                            Response.AddHeader("content-disposition", Convert.ToString((Convert.ToString("attachment; filename=") & Utility.GenerateReportName(StringUtility.AshDailyConsolidateReportName, "xls"))))
                            Response.BinaryWrite(bytes)
                            Response.Flush()
                            Response.Close()

                            Return New EmptyResult()
                            'Return File(bytes, StringUtility.ApplicationExcel, Utility.GenerateReportName(StringUtility.AshDailyConsolidateReportName, "xls"))
                        Catch ex As Exception
                            tblExceptionLogBL.Instance.Insert("AshDailyReport", "Export2", ex)
                            TempData(StringUtility.ErrorMessage) = "There is some problem while processing your request. Please try again later !!!"
                        End Try

                    Else
                        Dim bytes() As Byte = Utility.ReportToPDF(localReport)
                        Return File(bytes, StringUtility.ApplicationPdf, Utility.GenerateReportName(StringUtility.AshDailyConsolidateReportName, "pdf"))
                    End If
                Else
                    TempData(StringUtility.ErrorMessage) = StringUtility.Record_Not_Found
                End If
            Catch ex As Exception
                tblExceptionLogBL.Instance.Insert("AshDailyReport", "Export", ex)
                TempData(StringUtility.ErrorMessage) = StringUtility.Failure_General
                CustomException.HandleException(ex)
            End Try
            Return RedirectToAction("Index")
        End If
        Return View("~\Views\AshDailyConsolidateReport\Index.vbhtml", model)
    End Function

任何人请检查并让我知道，我错过了什么和哪里。另请告诉我是否需要任何与IIS相关的配置。