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Error: The type 'Syncfusion.Web.UI.WebControls.Tools.TabStripItem' exists in Syncfusion.Tools.Web assembly in multiple location

Platform: ASP.NET Web Forms (Classic) |
Control: General


Compiler Error Message: CS0433: The type 'Syncfusion.Web.UI.WebControls.Tools.TabStripItem' exists in both 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\02fac2e9\4fd1d854\assembly\dl3\47ca03ca\009d39b7_341bd001\Syncfusion.Tools.Web.DLL' and 'c:\Windows\Microsoft.NET\assembly\GAC_MSIL\Syncfusion.Tools.Web\v4.0_12.4451.0.24__3d67ed1f87d44c89\Syncfusion.Tools.Web.dll'


The error arises when multiple assembly versions are referred in the same application from GAC or bin folders.


To resolve the issue, refer to the corresponding assemblies to add Syncfusion ASP.NET controls in the web applications and ensure whether the assembly version matches the web.config file and the referred DLLs. Maintain the same assembly version throughout the project.

Table for .NET framework and corresponding Assembly versions.

 .Net Frame Work Version

Syncfusion DLL Reference







Check the registered assembly version in the ASPX page and web.config file and they should match the referred assembly version. The project file should also be referred to the corresponding assembly version in the project.

You can refer to the following code example.





Note: The assembly version referred should match with the specified version in ASPX page, webconfig and in project file.

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