The security validation for this page is invalid. Click Back in your Web browser, refresh the page, and try your operation again.

System.Exception: Microsoft.SharePoint.SPException: The security validation for this page is invalid. Click Back in your Web browser, refresh the page, and try your operation again. ---> System.Runtime.InteropServices.COMException (0x8102006D): The security validation for this page is invalid. Click Back in your Web browser, refresh the page, and try your operation again.
   at Microsoft.SharePoint.Library.SPRequestInternalClass.DeleteSite(String bstrUrl, Boolean bDeleteADAccounts)
   at Microsoft.SharePoint.Library.a.c(String A_0, Boolean A_1)
   --- End of inner exception stack trace ---
   at Microsoft.SharePoint.Library.a.c(String A_0, Boolean A_1)
   at Microsoft.SharePoint.SPSite.Delete()
   at Service.deleteSTSSite(String strSiteName)
   at Service.deleteSTSSite(String strSiteName)
   at Service.deleteSite(String strSiteName, String strUserName, String strPassword) 

Solution:

The SPSite.AllowUnsafeUpdate and SPWeb.AllowUnSafeUpdate properties must be set to true

site.AllowUnsafeUpdate = true

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