Select KeyValuePair in a ComboBox with Key

Question

I have several KeyValuePair in a combobx.

this.cbEndQtr.Items.Clear();
this.cbEndQtr.Items.Add(new KeyValuePair<int, string>(1, "Test1"));
this.cbEndQtr.Items.Add(new KeyValuePair<int, string>(2, "Test2"));

What's the simplest way to select the by passing in the key. For example something like this:

this.cbEndQtr.SelectedItem = 2;

score 4 · Answer 1 · edited Feb 28 '14 at 23:08

4

Here is a brute force approach:

void selectByKey(int key)
{
    foreach (var item in cbEndQtr.Items)
        if (((KeyValuePair<int, string>)item).Key == key) 
        {
            cbEndQtr.SelectedItem = item;
            break;
        }
}

And I just found this one line approach:

cbEndQtr.SelectedItem = cbEndQtr.Items.OfType<KeyValuePair<int, string>>().ToList().FirstOrDefault(i => i.Key == key);

Although if it doesn't find a match nothing will change.

edited Feb 28 '14 at 23:08

Mikael Dúi Bolinder

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answered Feb 28 '14 at 22:57

MikeH

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Nothing will change in your `for` loop, but your 'one line' approach sets the selected item to `null` if none is found. – Silvermind Feb 28 '14 at 23:30
@Silvermind `KeyValuePair` isn't nullable so you end up trying to set `SelectedItem` to a new instance of `KeyValuePair` (the default value). In my quick test if something was already selected it stayed selected. – MikeH Feb 28 '14 at 23:33
My bad, didn't notice that. – Silvermind Mar 01 '14 at 08:55

score 3 · Answer 2 · answered Feb 28 '14 at 22:56

I think you can use LINQ like this:

var key = 2; // get key from somewhere

var items = this.cbEndQtr.Items.OfType<KeyValuePair<int, string>>()
             .Select((item,index) => new { item, index);

var index = items.Where(x => x.item.Key == key).Select(x => x.index).First();        

this.cbEndQtr.SelectedIndex = index;

Select KeyValuePair in a ComboBox with Key

2 Answers2