Re: Good Practice on ListBox
From: Hemang Shah (hemang_at_hemang.net)
Date: 01/26/05
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Date: Wed, 26 Jan 2005 08:10:02 -0500
Hello Bill
You are welcome :)
Ok, your article worked, but it didn't work for me because I don't know how
to make it work for me!
I created a DataView dvClient and assisnged it to a table in my dataset -
tblClient, I did this in GUI:
//
// dvClient
//
this.dvClient.Table = this.dsClient.tblClient;
//
Next I used your article to come up with this:
private void frmClient_Load(object sender, System.EventArgs e)
{
DataColumn dcFullName = new DataColumn();
this.daClient.Fill(this.dsClient);
this.daChild.Fill(this.dsClient);
this.daClientAddress.Fill(this.dsClient);
dcFullName.DataType = System.Type.GetType("System.String");
dcFullName.ColumnName = "FullNameFN";
dcFullName.Expression = "GivenName + ' ' + LastName";
this.dsClient.tblClient.Columns.Add(dcFullName);
this.dvClient.Sort = "GivenName";
//lstName.DataSource = dvClient;
lstName.DisplayMember = "FullNameFN";
//lstName.ValueMember = "tblClient.ClientID";
}
Now, if I set the datasource of the listbox to the dataview "dvClient" the
sorting works just fine. But in your example you have set it to the
datatable, when I do that ("dsClient.tblClient"), the sort doesn't work.
I wanna ask you a question here, which is confusing me:
1) Is the table created in the dataset is technically a DataTable? I mean
DataColumn makes DataRow and DataRow makes DataTable and DataTable makes
DataSet. Because in your example you pointed the DataView to a DataTable:
dvEmployees = dtEmployees.DefaultView;
So although when you generate your database you have your dataset filled
with tables aren't those DataTable ?
2) The reason I wanted the datasource of the listbox to be the dataset it
because that would sync with my form as and when I change the values. (which
is the purpose of the listbox). You did suggest the usage of selecteditem,
there is a sample in 101 c# examples which demonstrates this. But if I can
just get away having the same datasource, its easy.
3) Although the method described in your article, if datasource is pointed
to the DataView (dvClient) works like a charm, there is one issue, most of
the time, when ppl want s'thing sorted on the field, they would want that
field to be displayed first. I guess I would just have to create another
DataColumn with another expression and change the DisplayMember of the
listbox correct ? I guess it wouldnt be suggested to change the expression
of the already displayed data and sort it, I don't know what is recommended.
4) Another Issue i'm having and I cannot seem to find the answer anywhere,
is that all example I see on the net for master child form navigation is
with the child data displayed in a grid. What if I want to display child
data all in text boxes, with its own navigation control (prev,next). Text
boxes doesn't have a datasource property to point to the relation object.
>From my searching I guess it would take some CurrencyManager Magic, but
without an example its pretty hard to digest that. Or I could be wrong and
there is another method.
Also when I'm trying to pick up a book, most ADO.NET books are from 2002, we
are in 2005, are those books still the best way to go ? I can't find a book
which will teach ADO.NET on Visual Studio, like make a fully functional
application as you worth through the book.
I bought Mastering C# Database Programming, which is I agree very good on
the theory of ADO.NET it also has examples to go with Visual Studio.net but
they are hardly useful, he has 1 example at the end of each chapter...
Any insight into my issues would be a boon!
Thank you again.
Hemang.
"W.G. Ryan eMVP" <WilliamRyan@NoSpam.gmail.com> wrote in message
news:%236XDOczAFHA.2540@TK2MSFTNGP09.phx.gbl...
> Hemang - thank you. It depends on how you have things set up. If the
> data
> in the list box is in the same dataset as the rest fo the stuff on the
> form - you can just add your datacolumn to it and bind the listbox
> accordingly. If there is a field between the dataset and datatable taht's
> common - just include everything in the same dataset and use a
> DataRelation
> object to link them together. Another thing you can do is use the
> SelectedIndex for instance of the listbox to set the Position property of
> the BindingContext.
>
> I think thought that whatever approach you use- sticking the datatalbe in
> the dataset with the rest of the data is probalby the way to go.
>
> Let me know if you have any problems.
>
> Bill
>
> --
> W.G. Ryan MVP (Windows Embedded)
>
> TiBA Solutions
> www.tibasolutions.com | www.devbuzz.com | www.knowdotnet.com
> "Hemang Shah" <v-hshah@microsoft.com> wrote in message
> news:euDeu4sAFHA.1084@tk2msftngp13.phx.gbl...
>> Those were some of the best articles I've read!
>>
>> Ok I got my box to sort on the fly, but now my listbox is bound to the
>> datatable and my form is bound to the dataset. So when I select any item
> in
>> the list box, the records on the form is not changed.
>>
>> How can I utilize that feature ?
>>
>> Thanks
>>
>>
>> "W.G. Ryan eMVP" <WilliamRyan@NoSpam.gmail.com> wrote in message
>> news:%236nw%23smAFHA.2640@TK2MSFTNGP14.phx.gbl...
>> > Ac tually, for this task you might want to consider an ExpressionColumn
>> > and
>> > Binding to it
>> >
>> > http://www.knowdotnet.com/articles/dataviews1.html
>> >
>> > This way you can sort as you please, it will be updated immediately if
> the
>> > underlying data changes, and you aren't pulling over erroneous data.
>> >
>> > --
>> > W.G. Ryan MVP (Windows Embedded)
>> >
>> > TiBA Solutions
>> > www.tibasolutions.com | www.devbuzz.com | www.knowdotnet.com
>> > "Hemang Shah" <hemang@hemang.net> wrote in message
>> > news:fZqdnfHmWvTH6mjcRVn-3A@rogers.com...
>> >> Greetings
>> >>
>> >> I want to display a listbox on the form which will include two columns
>> > from
>> >> the data table" FirstName" & "LastName"
>> >>
>> >> What I've done now, is modify the DataAdapter to include two
>> >> additional
>> >> colums as:
>> >>
>> >> [FirstName] + " " +[LastName] As NameFN
>> >> [LastName] + " " +[FirstName] AS NameLN
>> >>
>> >> I've selected NameFN as the DisplayMember of the listbox
>> >> However, I've also selected the Sort option to be true
>> >>
>> >> So what I see on the listbox doesn't correspond to the record selected
> on
>> >> the form.
>> >>
>> >> The record is selected automatically on the form because my DataSource
>> >> Property is bound to the dataset object.
>> >>
>> >> Is this a good practice ?
>> >>
>> >> Or its better to create a dynamic Array List on loadup and use that ?
>> >>
>> >> If that is the case how can I make the list selection, make the record
> on
>> >> the form change ?
>> >>
>> >> Thanks
>> >>
>> >>
>> >>
>> >>
>> >>
>> >
>> >
>>
>>
>
>
- Next message: Elton Wang: "Error joining tables from separate db's using SqlCommand object"
- Previous message: Łukasz Margielewski: "string name = dataSet.GROUP.FindByID_GROUP(id_group).GROUP_NAME invokes NullReferenceException"
- In reply to: W.G. Ryan eMVP: "Re: Good Practice on ListBox"
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