The report definition is not valid. Details: The report definition has an invalid target namespace

Question

The report definition is not valid. Details: The report definition has an invalid target namespace \'http://schemas.microsoft.com/sqlserver/reporting/2016/01/

Answer 1

Many have answered various permutations of this question by telling people to edit headers of old RDLC reports. This is a horrible idea. Generally, this issue materializes because you are using an version of the Microsoft.ReportingServices.ReportViewerControl.WebForms dll that is not compatible with the Sql Server/ Sql server lite that you are trying to run the report due to:

1. Upgrading versions of visual studio and are using the newer report template with the older .dll
2. Pulling code from a repository that was developed by someone using an older version of the .dll and you are editing it in a newer version of visual studio

The solution is to upgrade the version of the .dll through nuget. Visual Studio 2017 requires version 140.xxx.xx (which is compatible with Sql Server 2016 and previous versions). Look for Microsoft.ReportingServices.ReportViewerControl.WebForms.140.340.80