Filtering SQL Query using predefined filters - asp.net

Question

I've pasted my code below. What I'm trying to do is filter a set of data using the day. The 'day' field is stored as the abbreviated day name, so "thu" for Thursday etc. This works perfectly fine, except once you've changed the date filter to something else, the option for the current day doesn't work.
For example, today is Sunday. When the page loads, it filters out all listings that are not for Sunday, as it should. On a small group of LinkButton controls, if you click any other day of the week, it will change and show the option for the selected day, again, as it should do. However, when you try and set the filter to Sunday again, or click the "today" button, it won't change.
Based on my code, can anyone see what is wrong? If it is of any help, my data is on a remote SQL server.
VB Code:
Dim DateVal As Date = DateTime.UtcNow()
Dim DateName As String = DateVal.ToString("ddd")
Protected Sub btnMon_Click(sender As Object, e As EventArgs) Handles btnMon.Click
SqlDataSource1.SelectParameters("FiltDay").DefaultValue = "Mon"
End Sub
Protected Sub btnTue_Click(sender As Object, e As EventArgs) Handles btnTue.Click
SqlDataSource1.SelectParameters("FiltDay").DefaultValue = "Tue"
End Sub
Protected Sub btnWed_Click(sender As Object, e As EventArgs) Handles btnWed.Click
SqlDataSource1.SelectParameters("FiltDay").DefaultValue = "Wed"
End Sub
Protected Sub btnThu_Click(sender As Object, e As EventArgs) Handles btnThu.Click
SqlDataSource1.SelectParameters("FiltDay").DefaultValue = "Thu"
End Sub
Protected Sub btnFri_Click(sender As Object, e As EventArgs) Handles btnFri.Click
SqlDataSource1.SelectParameters("FiltDay").DefaultValue = "Fri"
End Sub
Protected Sub btnSat_Click(sender As Object, e As EventArgs) Handles btnSat.Click
SqlDataSource1.SelectParameters("FiltDay").DefaultValue = "Sat"
End Sub
Protected Sub btnSun_Click(sender As Object, e As EventArgs) Handles btnSun.Click
SqlDataSource1.SelectParameters("FiltDay").DefaultValue = "Sun"
End Sub
Protected Sub btnAll_Click(sender As Object, e As EventArgs) Handles btnToday.Click
SqlDataSource1.SelectParameters("FiltDay").DefaultValue = DateName
End Sub
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
SqlDataSource1.SelectParameters("FiltDay").DefaultValue = DateName
End Sub
TSQL (If it helps)
SELECT Schedule.SlotID, RIGHT('00' + CONVERT(VARCHAR(2), Schedule.StartHr), 2) + ':' + RIGHT('00' + CONVERT(VARCHAR(2), Schedule.StartMin), 2) AS StartTime,
Schedule.ProgrammeID, Schedule.Day, RIGHT('00' + CONVERT(VARCHAR(2), Schedule.EndHr), 2) + ':' + RIGHT('00' + CONVERT(VARCHAR(2), Schedule.EndMin), 2)
AS EndTime, Programmes.ProgrammeName, Programmes.Description, Programmes.PresenterID, Presenters.PresenterName, Presenters.PhotoURL
FROM Presenters CROSS JOIN
Programmes CROSS JOIN
Schedule
WHERE (Schedule.Day = #FiltDay)

Answer 1

maybe it is not 100% related to your issue but you should not handle the datasource initialization on the event of a different control.
your need is to fill the sql parameter so you should handle the Selecting event of the datasource.
on click of your buttons set the proper value for your variable DateName and on selecting of the datasource fill the sql parameter using your variable.
acting this way you can easily spot the actual value fed into the call and identify the issue.