如何比较datetime和datepicker中的值？

Question

I need to compare the chosen date with the date in a database and return values within the date range but keep getting incorrect format. The date format in the database is 2016-01-02 00:00:00.000 (from one of the rows)

I am using the code below but am unable to compare and keep getting"String was not recognized as a valid DateTime." Help?

protected void RadPushButton1_Click(object sender, EventArgs e)
    {
        DateTime startDate = DateTime.Parse(RadDatePickerStart.SelectedDate.ToString());
        string s = startDate.Date.ToString("yyyy-dd-MM");
        startDate = DateTime.Parse(s+"12:00:00 AM");
        // DateTime endDate = DateTime.Parse(RadDatePickerEnd.SelectedDate.ToString());
        EMCSettlementManager man = new EMCSettlementManager();
        Grid.DataSource = man.GetSTL010(r => EntityFunctions.TruncateTime( r.settlement_date) >= startDate);
        Grid.DataBind();
    }

Answer 1

If you want to compare dates, make sure all values are of type DateTime , not String .

Try something like this:

DateTime startDate = RadDatePickerStart.SelectedDate;
EMCSettlementManager man = new EMCSettlementManager();
Grid.DataSource = man.GetSTL010(r => r.settlement_date >= startDate);

If you want to get rid of the time-part, you could do something like this:

DateTime startDate = RadDatePickerStart.SelectedDate.Date;

If the field in the database is a string-type, not a datetime, please convert it to a Date(Time)-type. Using strings everywhere is a bad choise, alsnog known as 'stringly typed'. (See: https://blog.codinghorror.com/new-programming-jargon/ )