Hi Mohad,
I was able to reproduce the issue attached in D-trac. This is because the Syncfusion .core dll pointing to the older version of assembly in references folder of the project.
Please follow the steps to solve the issue.
1) Delete the output folders (bin and debug folders) of the project.
2) Run the AssemblyManager from the Start --> All Programs --> Syncfusion --> Essential Studio 4.4.0.46 --> Utilities --> Assembly Manager.
3) In the AssemblyManager, select the "Remove All Versions" option and then click "Perform Action". This will remove all the Syncfusion assemblies from GAC(C:\Windows\Assembly) and public assemblies folder({Install Drive}:\Program Files\Microsoft Visual Studio 8\Common7\IDE\PublicAssemblies).
4) Select the "Install version 4.4.0.46" option and then click the "Perform Action". This will install the Syncfusion assemblies of version 4.4.0.46 in the GAC and the public assemblies folder.
5) Open the application and remove the Syncfusion.core dll and re-add the Syncfusion.core dll from the public assemblies folder ([Installed Drive]:\Program Files\Microsoft Visual Studio 8\Common7\IDE\PublicAssemblies) and the "SpecifcVersion" property should be made false in property windiow. This will help the user to build the project with any 4.4.x.xx version of Syncfusion
6) Run the "Run License Manager" from Start --> AllPrograms --> Syncfusion --> Essential Studio 4.4.0.xx --> Utilities --> License Manager and note that you have valid key of v4.4 present in the license manager.
7) Rebuild and run the sample.
If the issue still exists then please follow the KB article. I hope this will solve your issue.
http://www.syncfusion.com/support/kb/studio/Default.aspx?ToDo=view&questId=35I hope this will solve your issue.
Thank you for your interest in Syncfusion products.
Regards,
Ramu