How to set a guid value to my ID which is of string type

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ASP.NET

C#5.0

Hi,
While I am adding a record I have defined the Id value.But every time it takes the default guid value..means only 00000000-0000-0000-0000-000000000000.Hence in db it store two data with same id.again when i delete the added record all the record are deleted as id=00000000-0000-0000-0000-000000000000,Can you please tell me how to avoid this prolem so that while adding a record it will store the data with some new guid values..
my codes are as follows

//Add Buttoon for adding record
    protected void btnAdd_Click(object sender, EventArgs e)
    {
        Guid id = new Guid();
        string Id = id.ToString();
        Member member = new Member();
      
        member.ID = Id;
        member.MemberID = int.Parse(txtMemberID.Text);
        member.ReceiptNo = txtReceiptNo.Text;
        member.SurName = txtSurName.Text;
        member.Name = txtName.Text;
        member.DateOfBirth = txtDateOFBirth.Text;
if (memberService.AddMember(member) == true)
            LoadData();

//load data method as follows
public void LoadData()
    {
        List<Member> members = memberService.GetAllMembers();
        gvMembers.DataSource = members;
        gvMembers.DataBind();