ASP.NET Pass multiple checkbox values into a SELECT query - asp.net

Question

I am working on displaying a students timetable based on possible Module choices. Each time a check box is selected I want to pass through the value selected "ModuleId" to use in a SELECT query to display the timetable for all modules selected. So if a user selects 3 check boxes the 'ModuleId' from each row selected will be passed into the SELECT query.
I don't know how to store each selected "ModuleId" and add it into my select query.
Below is how I retrieve the checked value:
<asp:TemplateField>
<ItemStyle HorizontalAlign="Center" Width="40px"></ItemStyle>
<ItemTemplate>
<asp:CheckBox ID="chkRow" runat="server" ToolTip='<%# Eval("ModuleId") %>' OnCheckedChanged="module_Changed" />
</ItemTemplate>
<asp:TemplateField>
Below is my method to display the value in a label (just for testing purposes):
protected void module_Changed(object sender, EventArgs e)
{
// Retrieve the check box ModuleId value to add to my SELECT query
string moduleid = ((CheckBox)sender).ToolTip;
}
Below is my method which contains the select query to display the timetable:
public String[] getModulesAtCurrentSlot(int timeslotInt, String moduleID, String Day)
{
List<String> modulesList = new List<string>();
if (conn.State.ToString() == "Closed")
{
conn.Open();
}
SqlCommand newCmd = conn.CreateCommand();
newCmd.Connection = conn;
newCmd.CommandType = CommandType.Text;
newCmd.CommandText = "SELECT DISTINCT Module.ModuleCode,ClassType.ClassTypeName,Convert(time,Class.StartTime), Convert(time,Class.EndTime),Building.BuildingName,RoomCode.RoomCode,Class.Color" +
" FROM Class INNER JOIN Module ON Class.ModuleId = Module.ModuleId INNER JOIN RoomCode ON Class.RoomCodeId = RoomCode.RoomcodeId INNER JOIN Building ON RoomCode.BuildingId = Building.BuildingId INNER JOIN Days ON Class.DayId = Days.DayID INNER JOIN ClassType ON Class.ClassTypeId = ClassType.ClassTypeId WHERE " +
" Module.ModuleId = " + moduleID + " AND Convert(Date,StartTime) = '" + Day + "' AND " + timeslotInt.ToString() + " BETWEEN ClassScheduleStartTimeId and ClassScheduleEndTimeId";
SqlDataReader dr = newCmd.ExecuteReader();
while (dr.Read())
{
String current = "<div class='slot' " + (!dr.IsDBNull(6) ? "style=\"background-color: " + dr.GetString(6) + ";\"" : "") + ">";
current += "<div class='line1'>" + dr.GetString(0) + " " + dr.GetString(1) + "</div>";// +"<br />";
current += "<div class='line2'>" + dr.GetTimeSpan(2).ToString().TrimEnd('0').TrimEnd('0').TrimEnd(':') + " - " + dr.GetTimeSpan(3).ToString().TrimEnd('0').TrimEnd('0').TrimEnd(':') + "</div>";// +"<br />";
current += "<div class='line3'>" + dr.GetString(4) + " " + dr.GetString(5) + "</div>";
current += "</div>";
modulesList.Add(current);
}
conn.Close();
return modulesList.ToArray();
}
On a previous page where the timetable is only displaying data for one ModuleId I've used the below query string to pass through the value.
String module_ID = "2";
if (Request.QueryString["module"] != null)
{
module_ID = Request.QueryString["module"];
}
else
{
Response.Write("Missing ?module=XX from url :(");
Response.End();// EndRequest;
}
DBAccess.cs screenshot:
Error screenshot:

Answer 1

If I understand correctly, you could have a session variable that contains a List of strings which holds all of the selected moduleID's
You could then use module_Changed event to add or remove moduleIDs from this List and then call getModulesAtCurrentSlot in a loop for each moduleid in the list and concatenate the returned string[]s into one longer string[] or List which you then display.
there may be some errors in the code below as I'm just doing it from memory but it should give you an idea!
protected void module_Changed(object sender, EventArgs e)
{
List<string> lst;
if( Session["lst"]!=null)
lst = (List<string>)Session["lst"];
else
Session.Add("lst", new List<string>());
// Retrieve the check box ModuleId value to add to my SELECT query
string moduleid = ((CheckBox)sender).ToolTip;
// add your own code to check if checkbox is checked or unchecked to see if you need to add or remove the ID from the list
// to add
if(lst.Contains(moduleid) == false)
lst.Add(moduleid);
// to remove - add your own code
List<string> lstResult = new List<string>();
foreach(var moduleID in lst)
{
lstResult.Add(getModulesAtCurrentSlot(timeslotInt, moduleID, Day));
}
// do something to display lstResult
// e.g. drag a Gridview control on your aspx page and bind the results list to it - this is just to give you a rough idea but you'll need to play around with it to get it to work as you want, and hopefully learn something in the process ;)
Gridview1.DataSource = lstResult;
Gridview1.Databind();
}