How to solve (Use of unassigned local variable)

Hi,

I am using Thought.vCards library to generate vCard contact but I am getting the following error:

Use of unassigned local variable 'vcard_writer'

Here is my code with thanks...

vCardPhone vphone1 = new vCardPhone("39753975", vCardPhoneTypes.Cellular);
vCardPhone vphone2 = new vCardPhone("17681768", vCardPhoneTypes.Work);

vCard my_vcard = new vCard();
my_vcard.Phones.Add(vphone1);
my_vcard.Phones.Add(vphone2);

vCardWriter vcard_writer;

vcard_writer.Write(my_vcard, "c:\\temp\\myvcard.vcf");