error in code........

Id  Email          Password     Name 
1  ali@yahoo.com    1234       ali                      is this row at position 0?
2  usman@yahoo.com  1234      usman                     is this row at position 1 ?

if (!Page.IsPostBack)
 {
            GetUserDetails(int.Parse(Request.QueryString["Id"].ToString()));
 }
 
public void GetUserDetails(int mu)
{
   string getUserDetail ="Select Id,Email,Name,Country FROM [User] where Id="+ mu+";
   dt = dbClass.ConnectDataBaseReturnDT(getUserDetail);
 
   if(dt.Rows.Count>0)//what this line do?
   {
      Label1.text=datatable.Rows[0]["Name"].Tostring();
      // i use for reterive the data from table User  1 ali@yahoo.com 1234 ali
 
      Label1.Text=datable.Rows[1]["Name"].Tostring();
      //i use for retrive the data from table User 2 usman@yahoo.com 1234 usman  
     // ERRRO COMES THERE IS NO ROW AT POSITION 1 
   }
}