Inject Custom Code in Crystal Report CS file for visual studio 2010

I am very new in Crystal Report environment. Can you please help me for following point?

I am using crystal Report for VS2010.[ASP.NET Project in C#]

I have a sample Report say “Report.rpt”.

In visual studio IDE I can see two file for that report like: “Report.rpt” and “Report.cs”.

Now, I have added some custom code in Report constructor in “Report.cs” file.

i.e

Public Report()
{

//My Code: Line 1;

//My Code: Line 2;

}

It works fine.

But,  if I change anything in report design, i.e.  In “Report.rpt” the “Report.cs” is getting Reset.

i.e. the custom written line in report constructor is vanished.

i.e.

Public Report()
{

}

Is it possible to inject any custom code in Crystal Report CS file?

Why the CS file is getting reset? Is there any way to stop it.

Thanks for any help/suggestion.

Regards

Abhisek