delete the record by passing null value in stored procedure

CREATE PROCEDURE usp_Delete
(
@UID int ,@FID  int =NULL
)
AS
BEGIN
SET NOCOUNT ON;

DELETE FROM TableName WHERE UID=@UID and  FID = @FID

END

void Delete(int uid, int? fid)
 {
     using (
       SqlConnection con =
           new SqlConnection(ConfigurationManager.ConnectionStrings["testConnectionString"].ConnectionString))
     {
         con.Open();
         using (SqlCommand cmd = new SqlCommand("usp_Delete", con))
         {
             cmd.Parameters.AddWithValue("@UID", uid);
             cmd.Parameters.AddWithValue("@FID", fid);
             cmd.ExecuteNonQuery();
         }

     }

 }