Bind a ComboBox to a generic Dictionary
This is too cool.
Often you have a ComboBox (or ListBox) whose items you want to "bind" to a list of values. In the world of .NET 2.0 we have this funky new generic Dictionary collection, but there's a trick to using it to bind. Here's the code:
var choices = new Dictionary<string, string>(); choices["A"] = "Arthur"; choices["F"] = "Ford"; choices["T"] = "Trillian"; choices["Z"] = "Zaphod"; comboBox1.DataSource = new BindingSource(choices, null); comboBox1.DisplayMember = "Value"; comboBox1.ValueMember = "Key";
Now you can set comboBox1.SelectedValue = "F" and it will display "Ford"! How cool is that?
# Trackback from Talking About Speech on 17/05/2007 4:29 AM
Comments
# Compgumby
26/05/2006 6:49 AM
This is the balls. Thanks for the tip. :)
# Nick
20/07/2006 12:10 AM
Bless you. You are a gentleman and a scholar.
# Carlo
8/09/2006 5:17 PM
Fantastic, just what we needed. Can't believe there isn't a combobox.items.add(text, value) like in ASP.NET :(
# Brian
11/11/2006 6:17 AM
Well done - this is exactly what I needed. You just saved me an hour.
# Dapuzz
13/03/2007 9:13 AM
Very nice, and very simple.
Can you teach us what the 'null' means there?
# mabster
13/03/2007 9:53 AM
You mean the second parameter to "new BindingSource"?
I think that second parameter the name of the property (of the first parameter) that you want to bind to. In this example I don't want to bind to a single property - I want to bind to the whole collection - so I pass null as the second param.
Hope this helps!
# The_Assimilator
29/03/2007 5:25 PM
I couldn't find any help on binding to a Dictionary on MSDN and was about to start trying various things before I stumbled across this article - many thanks, you've saved me a lot of time!
A small note: binding this way with a Dictionary<TKey, TValue> may work, but using a SortedDictionary<TKey, TValue> does not. However, using a SortedList<TKey, TValue> does work.
I wish the collections classes in .NET were better named...
# mabster
29/03/2007 6:01 PM
You're very welcome, The_Assimilator! That's what I love about blogs - free sharing of information to help each other out!
# Koka
28/05/2007 5:11 AM
HEY MAN - U'RE GREAT!
1000% what I'va needed at the moment!
Thanks a lot! God Bless U!
# Kothandaram
20/07/2007 3:21 PM
Hi,
Thanks a alot fo rthe post.
I just want to know the namespace for the class - "BindingSource".
Thanks in Advance.
# mabster
20/07/2007 5:14 PM
msdn2.microsoft.com/.../system.windows.forms.bindingsource.aspx
# Román
22/08/2007 5:21 AM
Thanks so muuuuch ! ! !
this post was very helpfull for me :)
Román
from Argentine..
# Yudiyana
27/08/2007 5:46 PM
Thanks. cool code.
# Noshirwan Sheriyarji
31/08/2007 6:09 AM
Thanks a lot, this has cut down my time a lot.
Nosh
# matt
18/10/2007 1:45 PM
Thanks. helped me out lots. Much better than using a DataTable for binding when all u want is a name/value pair. cheers.
# Nick
18/12/2007 3:40 AM
I can't tell you how much this helped me. I've looked everywhere for info on binding to a Dictionary. I was about to give up and convert my code to a basic list. This rocks!
# Queego
22/12/2007 1:31 PM
Thanks so much, this works great! I was going nuts trying to bind a Dictionary(Of Integer, BigHairyCustomClass) to a combobox (which works just fine in ASP.Net, by the way) until I found your article.
One note for VB.Net users:
the line should be:
.DataSource = new BindingSource(ch, Nothing)
rather than this, which I tried first:
.DataSource = new BindingSource(ch, vbNull)
Thanks again!
# Visar Elmazi
14/01/2008 8:54 PM
I was just about to write something that achieves this... and Voilà!
you have a perfect solution.
# sklett
22/01/2008 2:11 PM
Exactly what I was looking for!
I think I love you!
# sklett
22/01/2008 2:24 PM
Here's a little helper method for binding an enum to a combo:
public static IDictionary<int, string> DictionaryFromEnum(Type enumType)
{
Array values = Enum.GetValues(enumType);
IDictionary<int, string> buffer = new Dictionary<int, string>(values.Length);
for (int i = 0; i < values.Length; i++)
{
object value = values.GetValue(i);
buffer.Add((int)value, value.ToString());
}
return buffer;
}
# mabster
22/01/2008 4:54 PM
Nice work sklett! I could envision that as an extension method on Enum, so I could simply say myEnum.ToDictionary().
# James
31/01/2008 3:18 PM
Thanks. However, I had to do something strange to get this to work in VS2008 / ASP.NET .... I had to add a reference to System.Windows.Forms to by web project?! in order to get access to the BindingSource namespace...
It works on my ASP.NET page using
.. code behind ...
DataList.DataSource = New BindingSource(nameDictionary,"")
DataList.DataBind()
... web page ...
<%#Container.DataItem.Key%>
<%#Container.DataItem.Value%>
# Vince
15/02/2008 10:47 AM
Saved me an hour, thanks
# alex
27/03/2008 1:51 AM
Hi
i need to convert WINFORM App. to ASP.NET 2.0
if it's good way to use class System.Windows.Forms.BindingSource in ASP.NET?
# mabster
27/03/2008 6:25 AM
Never done much ASP.NET, alex, so I can't help you there. Another reader might be able to though.
# question
29/03/2008 1:36 AM
Hi,
when you pass a null as second parameter, it throws an ArgumentNullException, anyway to get around that?
# Ray
9/04/2008 3:22 AM
I was getting the ArgumentNullException too. My mistake was the order of initialization. I was binding my combobox and then adding the dictionary items. Didn`t realize at first. It`s working well with SortedDictionary also, I haven`t encounter Assimilator`s problem. Thanks a lot mabster, very helpful!
# Metal Mike
10/04/2008 3:51 AM
I WAS KILLING MY SELF TRYING TO DO SOMETHING LIKE THIS. YOU ARE THE MAN!
# Dave Bonner
15/04/2008 9:38 PM
Excellent tip.
Ok here's a variant on this to bend your heads around.
I won't go into great depths explaining what I'm trying to do here otherwise this post will be about 20 pages long, but:
If I've got a dictionary of (string, someClass)
I want to use the keys in the dictionary as FIELDS for a datagrid, and have it pull out the values from the dictionary as the field values.
How would you go about doing THAT?
Cheers
# Soumya
18/04/2008 1:48 AM
Thank You very much sir..
You saved my time....It helped me..
# alex
16/06/2008 10:23 PM
cool. thnx
# cristian
29/07/2008 3:07 AM
Amazing! Thanks a lot.
Regards from Buenos Aires.
# Hans
30/09/2008 1:58 PM
Thanks to everyone!! All the info was very helpful!
From Chile!
# xr280xr
10/10/2008 4:58 AM
Your domain is appropriately named.
# beyond
6/11/2008 1:53 PM
thanks a lot!
Indeed, you are a genius!
a boy from china!
nice to meet u!
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