Combobox "Select All" in linq query

Question

I have multiple comboboxes that pass a value to a linq query. Previously I was handling it with

    if(combobox.text == "select all")
       {combobox.text = "")

And then using the StartsWith(combobox.text) method to do the comparison, I know this is wrong. Since "jim" would return "Jimmy". How do I select all when "select all" is selected?

May help http://stackoverflow.com/questions/934241/listbox-select-all-items — PiLHA, Aug 09 '13 at 18:55

lc. · Accepted Answer · 2013-08-09T19:01:25.567

2

The best would be to conditionally add the query filter:

var query = dataSource.foo.AsQueryable();
//you may or may not need AsQueryable() depending on what "foo" is
//if it is not queryable, you may need AsEnumerable(), or simply nothing

if (!combobox.Text.Equals("select all"))
    query = query.Where(x => x.Equals(combobox.Text));

return query.ToList();

The "simpler" way would be to use a boolean or, but the resulting query is uglier and may or may not be translatable to SQL (if that is what you are using):

var query = dataSource.foo
    .Where(x => combobox.Text.Equals("select all") || x.Equals(combobox.Text));

edited Aug 09 '13 at 19:01

answered Aug 09 '13 at 18:55

lc.

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That's what I thought it was gonna come to, hoping there was a simpler way. – user2525463 Aug 09 '13 at 18:57
I've demonstrated the "simpler" way, using an or-expression, but it's probably not the better choice unless you know that the optimizer will remove the superfluous comparisons – lc. Aug 09 '13 at 19:00
Thought about it for a bit and came up with a lazy way that should work 99.9999% of the time StartsWith() && EndsWith() – user2525463 Aug 09 '13 at 19:48
@user2525463 Be careful if you're using Linq to SQL because EndsWith cannot use indexes. – lc. Aug 10 '13 at 02:36
@Ic Using Linq to xml – user2525463 Aug 12 '13 at 12:30

Combobox "Select All" in linq query

1 Answers1