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Syncfusion .NET Framework 4.5.1 and 4.5 assemblies will be compatible with .Net Framework 4.5.2
Framework 4.5.1 is disabled because, starting with version 16.4.0.* (2018 Volume 4), Syncfusion has removed the .NET Framework 2.0, 3.5, 4.5.1 and MVC3 assemblies and provide the separate Framework Add-On installer for licensed customers alone.
Find more details to get the 4.5.1 assemblies from Framework Add-On installer
Note: Ensure that all the referred Syncfusion assemblies are in same .Net Framework in your project