How to make auto generate number for text box in C#

Question

I want to Insert auto generate number show in textbox when form is loaded (like 000000001) in database that not define primary key and if table number found 0 then it increment every time when form open by user to entry data. Please help me how to do it. I am using C#. Thanks

its working , but I need to from table filed.

public void RetriveWorkRequestNo ()
    {
        try
        {
            string query = "SELECT IDENT_CURRENT('WorkRequests')";
            if (conn.State == ConnectionState.Closed)
            {
                conn.Open();

            }
            SqlCommand cmdwr = new SqlCommand(query, conn);
            SqlDataReader reader = cmdwr.ExecuteReader();
            while (reader.Read())
            {
                int value = int.Parse(reader[0].ToString()) + 1;
                textWorkRequestNo.Text = value.ToString("0000000000");
                textWorkRequestNo.ReadOnly = true;
            }
        }
        catch (Exception)
        {
            throw;
        }
        finally
        {
            if (conn.State == ConnectionState.Open)
            {
                conn.Close();
            }
        }

Answer 1

Finally I have done it using Sequence in MS SQL Server 2012

private int RetriveWorkRequestID()
    {

        try
        {
            string query = "SELECT NEXT VALUE FOR sqWorkRequests";
            if (conn.State == ConnectionState.Closed)
            {
                conn.Open();

            }
            using (SqlCommand cmd = new SqlCommand(query, conn))
            {
                using (SqlDataReader reader = cmd.ExecuteReader())
                {

                    while (reader.Read())
                    {
                        int value = int.Parse(reader[0].ToString());
                        string date = DateTime.Now.ToString("yyMM");
                        WorkRequestID = Convert.ToInt32(date.ToString() + value.ToString("000"));
                    }
                }

            }

        }

        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
        finally
        {

            if (conn.State == ConnectionState.Open)
            {
                conn.Close();
            }

        }
        return WorkRequestsID;
    }