The question is not new, but maybe for others with same problem, My answer be useful, too. In web.config
=> configuration
=> configSections
section paste a new config for telerik report, if you don't have:
<section
name="Telerik.Reporting"
type="Telerik.Reporting.Configuration.ReportingConfigurationSection, Telerik.Reporting, Version=11.0.17.118, Culture=neutral, PublicKeyToken=a9d7983dfcc261be"
allowLocation="true"
allowDefinition="Everywhere"/>
Use your telerik verion in version
attribute. you can find it from Solution Explorer
=> your project name
=> References
=> TelerikReporting
=> Properties
And Also, in <configrations>
body, paste:
<Telerik.Reporting>
<extensions>
<render>
<extension name="RTF" visible="false">
</extension>
<extension name="PDF" visible="false">
</extension>
<extension name="CSV" visible="false">
</extension>
<extension name="IMAGE" visible="false">
</extension>
<extension name="MHTML" visible="false">
</extension>
<extension name="XPS" visible="false">
</extension>
</render>
</extensions>
</Telerik.Reporting>
In code above I disabled any export type, except for Excel.