ASP.NET Retrieve value from Checkbox onCheckChanged - asp.net

Question

I am working on displaying a students timetable based on possible Module choices. (See Screenshot) Currently I am displaying all available modules in a gridview which the student can select by using check boxes. I have already created the insert query to insert their selection to the database. (2)
However, each time a check box is selected I want to retrieve the 'ModuleId' to add to a SELECT query which displays a timetable of their selected modules. (1)
So if a user selects 3 check boxes the 'ModuleId' from each row selected will be passed into the SELECT query.
Below is my method which enables the timetable for specific a ModuleId to be displayed:
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();
}
How would I pass all selected values (ModuleId) from the checkboxes to be used in my above select query as previously for displaying just one module I used
' Module.ModuleId = " + moduleID ' ?

Answer 1

To complete what you are trying to do efficiently and without big foreach loops you need to change the whole way your user inputs data in to the gridview.
I believe that you should be utilising the GridViews OnRowUpdating Event, When a row is updated, using this event you already have context of which row has changed. e.RowIndex - Gets the index of the row being updated
Utilising this event will require a bit of a redesign of your gridview fields, You will need to add a EditItemTemplate tag in each TemplateField Add a CommandFieldand using OnRowUpdating re-write your update event. Its to much information to post in a answer, This information should help you get started on using the GridView events to their full potential.
On a side note you should use paramerterized queries in your sql.
EDIT
Based on your clarification that you need to retrieve the moduleid for each checkbox, I am going to make a few assumptions so it might not work without some tweaks.
To start with try this:
<asp:TemplateField>
<ItemStyle HorizontalAlign="Center" Width="40px"></ItemStyle>
<ItemTemplate>
<asp:CheckBox ID="chkRow" runat="server" ToolTip='<%# Eval("ModuleId") %>' OnCheckedChanged="module_Changed" />
</ItemTemplate>
Using '<%# Eval("ModuleId") %>' Will populate the tooltip for the checkbox with the ModuleID value during the GridView.DataBind() function. Iam making the assumption that the column name is exactly "ModuleId"
Then in the code behind you can read the tooltip value of the checkbox like this:
protected void module_Changed(object sender, EventArgs e)
{
// Retrieve the check box ModuleId value to add to SELECT query
string moduleid = ((CheckBox)sender).ToolTip;
}
Now that when the gridview loads all the checkboxes have a tooltip that is populated with the ModuleID you can easily know which box is for which module by checking the tooltip.