When i was looking solution for the problem, i saw a topic on microsoft forums. The same question is asked by a user and i want to quote that question:
The Report Viewer control is not rendering the toolbar correctly.
I'm following the instruction Getting started with the ReportViewer
2016 control at https://msdn.microsoft.com/en-us/library/mt764770.aspx
and am able to run reports from my application, however there are
issues with the Report Toolbar.
- I'm not seeing the toolbar icons, even though the hyperlinks are active.
- When I open the Export dropdown the background is transparent and difficult to read.
- Report parameter dropdowns appear as textboxes, yet when I click them they act like dropdowns.
Attached is an image showing the toolbar as it is rendering in my
Are you using the control in a master/child page? There is a known issue with the current Report Viewer Control RC - https://github.com/Microsoft/Reporting-Services/blob/master/Docs/Get-Started-With-RVC.md#known-issues