I have written a code for event handler ('ItemAdding') for a list.
I want to display the custom error message. I am using the following
code for the same

properties.ErrorMessage = "some xxx";
properties.Status = SPEventReceiverStatus.CancelWithError;
properties.Cancel = true;

It is working fine, but the error message is displaying in a new
page. I want to display the error message in the same page instead of a
new page.

Is it possible to display the error message in the same page? If it is
possible please suggest the steps to achive the same.