add-in-set-null-reference-exception.md

title	page_title	description	type	slug	tags	ticketid	res_type
An AddInSet NullReferenceException Is Thrown on Requesting Reports	AddInSet NullReferenceException on Requesting Reports	Learn how to handle the AddInSet NullReferenceException thrown when requesting reports in Telerik Reporting.	troubleshooting	add-in-set-null-reference-exception	telerik, reporting, reportviewer, storage, addint, null, reference, exception, is, thrown	1173719	kb

Environment

Product

Progress® Telerik® Reporting

Description

An AddInSet NullReferenceException is thrown when the report viewer attempts to request a report.

Error Message

exceptionMessage: "Object reference not set to an instance of an object."
exceptionType: "System.NullReferenceException"
message: "An error has occurred."
stackTrace: "
	at Telerik.Reporting.Cache.CacheStorage.AddInSet(String key, String value)
	at Telerik.Reporting.Services.Engine.PersistableCollection`1.NewItem(String newID, Action`1 initializeObject)
	at Telerik.Reporting.Services.Engine.ReportEngine.RegisterClient()
	at Telerik.Reporting.Services.WebApi.ReportsControllerBase.RegisterClient()
	at Telerik.ReportServer.Web.Controllers.Api.ReportsController.<RegisterClient>b__2()
	at Telerik.ReportServer.Web.Controllers.Api.ReportsController.DoIfUserAvailable(Func`1 action)
	at Telerik.ReportServer.Web.Controllers.Api.ReportsController.RegisterClient()"

Solution

The stack trace shows that the exception happens when the REST service tries to interact with the storage. The method which throws the exception is AddInSet.

The following example demonstrates the implementation of AddInSet.

public void AddInSet(string key, string value)
{
	using (this.AcquireSetLock(key))
	{
		var raw = this.GetBytes(key);
		var set = null == raw ? new HashSet<string>() : SerializationUtils.Deserialize<HashSet<string>>(raw);
		if (set == null)
		{
			// Not localizable by design
			const string error = "Incorrect value (null) deserialized. Make sure you are using CacheStorage inside single-instance application deployment only.";
	
			System.Diagnostics.Trace.WriteLine(error);
			throw new ApplicationException(error);
		}
		set.Add(value);
		this.SetBytes(key, SerializationUtils.Serialize(set));
	}
}

The System.Diagnostics.Trace.WriteLine(error) code line means that if a trace listener is attached, the error message above will be present in the trace listener log.

The error message might mean that either the file storage got corrupted, or the service is in a multiple-instance environment (web farm environment) and the default implementation of the REST service storage FileStorage is not suitable for such environment.

Depending on the environment specifications, you can approach the issue in the following ways:

• In web farm environments, it is recommended to change the storage to use an MsSqlServerStorage or RedisStorage implementation. For further details, refer to the article on [IStorage implementation suitable for deploying in Web Farms]({%slug telerikreporting/using-reports-in-applications/host-the-report-engine-remotely/telerik-reporting-rest-services/rest-service-storage/overview%}).
• In single-instance environments, reset the report viewer storage data by deleting the contents of the file storage folder. By default, the REST Service is using the temporary folder of the current user. If you are using the Telerik Report Server, the default file storage is placed in the product installation folder, that is, in C:\Program Files (x86)\Progress\Telerik Report Server\Telerik.ReportServer.Web\Data. Delete only the folder with the randomly generated name and leave the TRS folder which contains the Report Server data intact.

It is recommended that you create a backup before resetting the storage.

See Also

• [REST Service Storage Overview]({%slug telerikreporting/using-reports-in-applications/host-the-report-engine-remotely/telerik-reporting-rest-services/rest-service-storage/overview%})
• [Configuring MS SQL Database Storage]({%slug telerikreporting/using-reports-in-applications/host-the-report-engine-remotely/telerik-reporting-rest-services/rest-service-storage/how-to-configure-an-mssql-database-storage%})
• [Using Redis Storage]({%slug telerikreporting/using-reports-in-applications/host-the-report-engine-remotely/telerik-reporting-rest-services/rest-service-storage/how-to-use-redis-storage%})