Thanks for contacting Syncfusion support.
We have analyzed your screenshot and we suspect that the issue is due to DLL Conflict. To avoid this issue, please make sure the following things before build your application.
1) Check if multiple versions of Syncfusion assemblies are referred in your project.
2) Delete bin and obj folders exists in the application directory.
3) Check your dll version in reference and webconfig file.
4) Check if you are referring proper dependent assemblies according to the .NET Framework.
We suggest you to follow the following knowledge base documentation,
For your reference we have created a simple sample requirement and same it can be downloaded from the following location.