Bitwise operations in Visual Basic .NET

I'm re-writing some old application in VB.NET to C# and ASP.NET 3.5. Everything is going OK but I have this problem - and, as the database will not be changed, I must find a solution to it.

The old app saves the list o desired days (from Sunday to Saturday) in a byte. This is the way it do it:

If chkDaily.Checked Then
            daysBitmask = 127    ' This is for a full week
        Else
            For i = 0 To chklstWeekly.Items.Count - 1
                If chklstWeekly.Items(i).Selected Then
                    ' List the selected items
                    daysBitmask += 2 ^ CInt(chklstWeekly.Items(i).Value)
                    daysBitmask = daysBitmask
                    Message2.InnerText = daysBitmask
                End If
            Next
        End If

and I converted it to

        if (rdbDaysList.SelectedValue == DAILY)
            daysBitmask = 127;
        //This is for a full week
        else
            foreach (var d in ckbDaysList.Items)
            {
                ListItem day = d as ListItem;
                if (day.Selected)
                {
                    daysBitmask += Convert.ToByte(Math.Pow(2, Convert.ToDouble(day.Value)));
                }
            }

This works. My biggest problem is to convert fr开发者_如何学Com the byte to the C# code. The original VB.NET is right above:

            If (dr("DesireDays").ToString() = "127") Then
                chkDaily.Checked = True
                chkWeekly.Checked = False
                chklstWeekly.Enabled = False
            Else
                chkWeekly.Checked = True
                chkDaily.Checked = False
                chklstWeekly.Enabled = True

                Dim AD As Integer = dr("DesireDays").ToString()
                Dim i As Integer

                For i = 0 To chklstWeekly.Items.Count - 1
                    If AD And 2 ^ i Then
                        chklstWeekly.Items(i).Selected = True

                    End If
                Next i

Any help will be appreciated.

You don't want to use ToDouble, as you want an int (that's what CInt gives you).

In addition, for doing powers of two, bitshifting is usually a little clearer than doing exponents (though choose whatever works for you).

As an aside, it's also usually safer to use a bitwise OR (the vertical | bar) rather than addition.

ListItem day = d as ListItem;

if (day.Selected)
{
    daysBitmask |= 1 << Convert.ToInt32(day.Value);
}

To answer the actual question, the reverse will work:

ListItem day = d as ListItem;

if ((daysBitmask & (1 << Convert.ToInt32(day.Value))) > 0)
{
    day.Selected = true;
}