How to have a trail of four zeros proceeding a field name from a table in display member property of combobox in c# windows forms with sql server 2008

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Hi my name is Vishal. For the past 2 days, I have been breaking my head on how to have a trail of four zeros proceeding a field name from a table in display member property of combobox in c# windows forms with sql server 2008?
I have a form named:frmDialyzer and in it I populate my combobox named:cboPatientID.
Given below is c# code on how I populate my combobox(cboPatientID) from tables named:patient_id and patient_name in sql server2008.:

namespace DRRS_CSharp
{
    public partial class frmDialyzer : Form
    {
int pUserID;
public frmDialyzer()
        {
            InitializeComponent();
 string Sql = "Select p.patient_id as patient_id,(n.patient_first_name+' '+n.patient_last_name+'| '+convert(varchar,n.patient_id)) as Name from patient_id p,patient_name n where n.patient_id=p.patient_id and n.status=1 and not exists(Select * from dialyser where dialyser.deleted_status=0 and dialyser.closed_status=0 and dialyser.patient_id=p.patient_id)";
            DataTable dt = new DataTable();
            SqlConnection conn = new SqlConnection("Data Source=NPD-4\\SQLEXPRESS;Initial Catalog=DRRS;Integrated Security=true");
            if (conn.State != ConnectionState.Open)
            {
                conn.Open();
            }
            SqlCommand cmd = new SqlCommand(Sql, conn);
            dt.Load(cmd.ExecuteReader());
            cboPatientID.DataSource = dt;
            cboPatientID.ValueMember = "patient_id";
            cboPatientID.DisplayMember = "Name";
            cboPatientID.SelectedValue = 0;
}

Since i am using SelectedValue property of cboPatientID in terms of selecting item in combobox(cboPatientID) in frmDialyzer. I have also enabled DropDownStyle property of cboPatientID to DropDownList in frmDialyzer.
Given below is structure of tables in sql server2008:
table name:patient_id
ColumnName DataType AllowNulls
patient_id(primary key) Int No(since auto-increment)
patient_sex nvarchar(15) Yes
patient_dob date Yes
row_upd_date datetime Yes

table name:patient_name
ColumnName DataType AllowNulls
patient_id int Yes
patient_first_name nvarchar(50) Yes
patient_middle_name nvarchar(50) Yes
patient_last_name nvarchar(50) Yes
status bit Yes
row_upd_date datetime Yes

As you can see in below c# code of frmDialyzer:

namespace DRRS_CSharp
{
    public partial class frmDialyzer : Form
    {
int pUserID;
public frmDialyzer()
        {
            InitializeComponent();
string Sql = "Select p.patient_id as patient_id,(n.patient_first_name+' '+n.patient_last_name+'| '+convert(varchar,n.patient_id)) as Name from patient_id p,patient_name n where n.patient_id=p.patient_id and n.status=1 and not exists(Select * from dialyser where dialyser.deleted_status=0 and dialyser.closed_status=0 and dialyser.patient_id=p.patient_id)";
            DataTable dt = new DataTable();
            SqlConnection conn = new SqlConnection("Data Source=NPD-4\\SQLEXPRESS;Initial Catalog=DRRS;Integrated Security=true");
            if (conn.State != ConnectionState.Open)
            {
                conn.Open();
            }
            SqlCommand cmd = new SqlCommand(Sql, conn);
            dt.Load(cmd.ExecuteReader());
            cboPatientID.DataSource = dt;
            cboPatientID.ValueMember = "patient_id";
            cboPatientID.DisplayMember = "Name";
            cboPatientID.SelectedValue = 0;
}

In above code, I am able to display patient first ,last name and patient_id as Name in DisplayMember property of cboPatientID
Suppose i want to display a trail of four zeros proceeding patient_id(such as if patient_id=2 then i want patient_id to be displayed as 00002) along with patient first,last name and patient_id as Name in DisplayMember property of cboPatientID.
So I am getting patient_id along with patient first,last name in DisplayMember property of cboPatientID.
But what i want is my patient_id must have trail of four zeros proceeding my patient_id
for example: my patient_id:3 then i want my patient_id to be displayed as 00003.

Can anyone help me please on how to display trail of four zeros proceeding my patient_id along with patient first,last name as Name in DisplayMember property of cboPatientID. Tell me what should i need to do to achieve my required result.?

Can anyone help me please?! Any help/guidance in solving of this problem would be greatly appreciated!