How to get address list form any email account using C#???

First You have to Download and install Google Data API setup From Google .

        private void btnConnect_Click(object sender, EventArgs e)

        {

           // Validate User input

            Username = txtUsername.Text.Trim();

            if (Username.Contains("@gmail.com") == false)

            {

                Username = Username + "@gmail.com";

            }

            Password = txtPassword.Text.Trim();

            //Start Process After Validating email

            if (Username != "" && Password != "")

            {

            RequestSettings rs = new RequestSettings("MyGoogleContactSoftware",Username, Password);

            rs.AutoPaging = true;

            ContactsRequest cr = new ContactsRequest(rs);

            //  Uri feedUri = new Uri(ContactsQuery.CreateContactsUri("default"));

            Feed confeed = cr.GetContacts();

            foreach (Contact c in confeed.Entries)

            {

                    listBox1.Items.Add(c.PrimaryEmail.Address);

            }

          }

          else

          {

          MessageBox.Show("Values are Mendatory","Warning",MessageBoxButtons.OK,MessageBoxIcon.Exclamation);

            }

}