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How to resolve the reference error, “The type or namespace name 'Accordion' does not exist in the 'Syncfusion.JavaScript.Web'"?

Platform: ASP.NET Web Forms |
Control: General |
Product Version:


While compiling the application, the reference error message “The type or namespace name 'Accordion' does not exist in the namespace 'Syncfusion.JavaScript.Web' (are you missing an assembly reference?)" appears.

 The following screenshot displays the error.

Error message

Figure 1: Error message


In order to avoid the Accordion does not exist issue, refer to the Syncfusion.EJ.Web assembly in the project. The following assembly information table helps you choose the correct assembly version.

Table 1: DLL Reference

 .NET Framework Version

Assembly Version(








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Nov 12, 2019

Hello, I'm getting this same type error for ALL SF assembly references since attempting to upgrade from 16.xx to via nuget.

I also tried downloading and installing that version from my control panel, and it always gets stuck at updating Visual Studio 17, and the toolbox now does not show any SF controls. I left the installer alone for hours, so I know it didn't just need more time, as this is a decent computer with 2 x Xeon processors and 24GB ram.

Currently I get this when I try to compile:

Error CS0234 The type or namespace name 'Web' does not exist in the namespace 'Syncfusion.JavaScript' (are you missing an assembly reference?) SonshineDBV2 D:\COASTALDATADEV...\Schools\Default.aspx.designer.cs 22 Active

What should I do to get this project working again? Currently I have installed Syncfusion.EJ, Licensing, JavaScript, and Reporting.WebForms, which I accidentally installed because I was looking for the other WebForms package, which I still can't find...


Ashokkumar Balasubramanian [Syncfusion]
Nov 19, 2019

Hi Jon,

Please find the details in attached documentation.


Regards, Ashokkumar B.

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