Selecting values in DDLs with values from SQL DB

On my page I have four drop-down lists: startWeek, startYear, endWeek and endYear which sets a period of time.The default values, that must be displayed on page load, are selected from a table called Period in a SQL database using a Linq.DataContext class called MyContextClass. The periods (a period is a week in a given year) in this table can be active/inactive. In the code I select two active periods: The one with the lowest ID (the earliest period) and the one with the highest ID (the latest period). I then try to display these two periods in the four drop downs: the first two lists contain the week and the year of the earliest period and the last two contain the week and the year of the latest period. I have two problems:

1. When the method below is called upon Page_Load, the method selects the end-values, that is, the end-week and the end-year, in both sets of drop-down lists! Fx. if the start period is week 32 in 2008 and the end period is week 12 in 2009, then "12" and "2009" is selected in both startWeek/startYear and endweek/endYear. However, if I call this method outside the PageLoad method, it works fine and displays the start- and end-periods correctly! what is wrong? I have debugged it, and it seems that the correct values are selected in the startweek/startYear drop-downs at first, but then overwritten later... I can't figure out why!

2. I choose the selected value in each drop down by looping through a IQueryable element although I know for sure, that it will only hold one element. How do I do this without the loop?

 

private void SetPeriods()
{
            MyContextClass db = new MyContextClass();

            var periods = from p in db.Periods
                          where p.Active
                          select new { p.ID, p.Name, p.Year };

            int startPeriodID = periods.Min(period => period.ID);
            int endPeriodID = periods.Max(period => period.ID);

            IQueryable startPeriodName = periods.Where(period => period.ID == startPeriodID).Select(period => period.Name);
            IQueryable endPeriodName = periods.Where(period => period.ID == endPeriodID).Select(period => period.Name);
            IQueryable startPeriodYear = periods.Where(period => period.ID == startPeriodID).Select(period => period.Year);
            IQueryable endPeriodYear = periods.Where(period => period.ID == endPeriodID).Select(period => period.Year);

            foreach (var p in startPeriodName)
            {
                this.StartWeekDdl.SelectedValue = p.ToString();
            }

            foreach (var p in startPeriodYear)
            {
                this.StartYearDdl.SelectedValue = p.ToString();
            }

            foreach (var p in endPeriodName)
            {
                this.EndWeekDdl.SelectedValue = p.ToString();
            }

            foreach (var p in endPeriodYear)
            {
                this.EndYearDdl.SelectedValue = p.ToString();
            }

}

0
epb1
10/27/2008 12:47:04 PM
asp.net.web-forms 93655 articles. 6 followers. Follow

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Have you tried using the FindByValue or FindByText methods of the DropDown list along with the Single() method to select the value instead of the loops? something like.

StartWeekDdl.FindByValue(startPeriodName).Selected = true --if you are putting the PeriodName in the value of the dropdown

or

StartWeekDdl.FindByText(startPeriodName).Selected = true --if you are putting the PeriodName in the text of dropdown

 

And use the Single() method rather than getting the values back as an IQueryable interface, something like

string startPeriodName = periods.Where(period => period.ID == startPeriodID).Select(period => period.Name).Single();

 

 

0
rodnex
10/27/2008 5:10:32 PM

Thanks for your response. The problem was infact, that I was using the same ListItem array to populate the StartWeekDdl and the EndWeekDdl and the same ListItem array to populate the StartYearDdl and the EndYearDdl. So, when the code updated the EndWeekDdl it updated the ListItem array of the StartWeekDdl too (as it was the same array), and thereby displayed the same item in both lists.

Anyway, the Single method was just was I was looking for. Thanks!

0
epb1
10/28/2008 8:27:43 AM
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