"Cannot implicitly convert type 'Lab06.Attendance' to 'System.Collections.Generic.List<Lab06.Attendance>" How to solve this error - asp.net

Question

AssignmentAttendance.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Web.Services.Description;
namespace Lab06 {
public partial class AssignmentAttendance : System.Web.UI.Page
{
Attendance aAttendance = new Attendance();
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
bind();
}
}
protected void bind()
{
List<Attendance> attendancelist = new List<Attendance>();
attendancelist = aAttendance.getAttendanceAll();
GridView1.DataSource = attendancelist;
GridView1.DataBind();
}
protected void Retrieve_Attendance_Click(object sender, EventArgs e)
{
string attributename = tb_classcode.ToString();
List<Attendance> attendanceList = new List<Attendance>();
attendanceList = aAttendance.getAttendance(attributename);
GridView1.DataSource = attendanceList;
GridView1.DataBind();
}
/* protected void edit_attendance(object sender, GridViewEditEventArgs e)
{
}*/
}
}
AssignmentContentUploadClass.cs
public class Attendance {
string _connStr =ConfigurationManager.ConnectionStrings["HealthDBContext"].ConnectionString;
private string _ClassCode = null;
private string _Teacher_ID = "";
private string _TeachingSessions = "";
private string _Remarks = "";
public Attendance()
{
}
// Constructor that take in all data required to build a Product object
public Attendance(string ClassCode, string Teacher_ID, string TeachingSessions, string Remarks)
{
_ClassCode = ClassCode;
_Teacher_ID = Teacher_ID;
_TeachingSessions = TeachingSessions;
_Remarks = Remarks;
}
public string ClassCode
{
get { return _ClassCode; }
set { _ClassCode = value; }
}
public string Teacher_ID
{
get { return _Teacher_ID; }
set { _Teacher_ID = value; }
}
public string TeachingSessions
{
get { return _TeachingSessions; }
set { _TeachingSessions = value; }
}
public string Remarks
{
get { return _Remarks; }
set { _Remarks = value; }
}
public int createAttendance()
{
int result = 0;
string queryStr = "INSERT INTO Attendance(ClassCode, Teacher_ID, TeachingSessions, Remarks)"
+ " values (#ClassCode, #Teacher_ID, #TeachingSessions, #Remarks)";
SqlConnection conn = new SqlConnection(_connStr);
SqlCommand cmd = new SqlCommand(queryStr, conn);
cmd.Parameters.AddWithValue("#ClassCode", this.ClassCode);
cmd.Parameters.AddWithValue("#Teacher_ID", this.Teacher_ID);
cmd.Parameters.AddWithValue("#TeachingSessions", this.TeachingSessions);
cmd.Parameters.AddWithValue("#Remarks", this.Remarks);
conn.Open();
result += cmd.ExecuteNonQuery(); // Returns no. of rows affected. Must be > 0
conn.Close();
return result;
}//end Insert
public Attendance getAttendance(string ClassCode)
{
Attendance attendanceDetail = null;
string Teacher_ID, TeachingSessions, Remarks;
string queryStr = "Select * From Attendance Where ClassCode = #ClassCode";
SqlConnection conn = new SqlConnection(_connStr);
SqlCommand cmd = new SqlCommand(queryStr, conn);
cmd.Parameters.AddWithValue("#ClassCode", ClassCode);
conn.Open();
SqlDataReader dr = cmd.ExecuteReader();
if (dr.Read())
{
Teacher_ID = dr["Teacher_ID"].ToString();
TeachingSessions = dr["TeachingSessions"].ToString();
Remarks = dr["Remarks"].ToString();
attendanceDetail = new Attendance(ClassCode, Teacher_ID, TeachingSessions, Remarks);
}
else
{
attendanceDetail = null;
}
conn.Close();
dr.Close();
dr.Dispose();
return attendanceDetail;
}
public List<Attendance> getAttendanceAll()
{
List<Attendance> attendancelist = new List<Attendance>();
string ClassCode, Teacher_ID, TeachingSessions, Remarks;
string queryStr = "SELECT * FROM Attendance Order By ClassCode";
SqlConnection conn = new SqlConnection(_connStr);
SqlCommand cmd = new SqlCommand(queryStr, conn);
conn.Open();
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
ClassCode = dr["ClassCode"].ToString();
Teacher_ID = dr["Teacher_ID"].ToString();
TeachingSessions = dr["TeachingSessions"].ToString();
Remarks = dr["Remarks"].ToString();
Attendance a = new Attendance(ClassCode, Teacher_ID, TeachingSessions, Remarks);
attendancelist.Add(a);
}
conn.Close();
dr.Close();
dr.Dispose();
return attendancelist;
}
}
I am not sure of the error and thus I am not able to provide much
I am trying use the getAttendance(ClassCode) function to retrieve the data based off my input of my classcode in the textbox of my AssignmentAttendance.aspx.
I am thinking of using the getAttendance function in my AssignmentAttendance.aspx file by passing in the data of my classcode entry from the textbox to retrieve the details of the Attendance based off classcode.
However, I am not too sure how that works and might need some help
My database has:
ClassCode
Teacher_ID
TeachingSessions
Remarks
If anything is missing or I did not make things clear do let me know
-Edit-
I am getting an error from my AssignmentAttendance.aspx.cs file
attendanceList = aAttendance.getAttendance(attributename);