how to remove some field in the text box in the login page

its not storing in the data base as emp0000001...it stores as 1..

string rem = txt_EId.Text;
string sa;
sa= rem.Replace("emp","");
int a = Convert.ToInt32(sa);
//MessageBox.Show(a.ToString());
SqlConnection s = new SqlConnection();
s.ConnectionString = @"Data Source=.;Initial Catalog=employee;User ID=sa;Password=tecfwds@hg25tr32";
s.Open();
string st = "select Employee_Id,Password from Employee_Details where Employee_Id='" +a.ToString() + "' and Password='" +txt_pwd.Text+ "'";
SqlDataAdapter da = new SqlDataAdapter();
DataTable dt = new DataTable();
SqlCommand cmd = new SqlCommand();
da.SelectCommand = new SqlCommand(st, s);
da.Fill(dt);
if (dt.Rows.Count > 0 && rem.Contains("emp"))
{
MessageBox.Show("login successfull");
}
else
{
MessageBox.Show("invalid user id and pass word");
}

this code works