Bind an Array of Custom Objects

[Guest]

I have a web service method that returns an array of custom objects marked
serializeable with fully described public properties.

When I bind the results to a DataGrid I can access the properties in the
ItemDataBound event of the codebehind but I can't access them declaratively
in the HTML code?

Here is the code to call the method.
net.mysite.www.WSInterface proxy;
proxy = new net.mysite.www.WSInterface();
ProjectList[] pl = proxy.getProjects("%",false,true);
this.DataGrid1.DataSource = pl;
this.DataGrid1.DataBind();

Here is the code to access the property in the Item databound event.
lbl.Text = ((ProjectList)dg.DataItem).ClientName;

Here is the code that won't work on the HTML side:
Option 1:
<asp:BoundColumn HeaderText="Client Contact"
DataField="ClientContact"></asp:BoundColumn>

Option 2:
<asp:TemplateColumn HeaderText="Contact">
<ItemTemplate><%# DataBinder.Eval(Container.DataItem,
"ClientContact")%></ItemTemplate>
</asp:TemplateColumn>

Here is the error:
DataBinder.Eval: 'net.mysite.www.ProjectList' does not contain a property
with the name ClientContact.

Why can I access the property in the ItemDataBound event but not on the
declarative side?

The Page obviously know what kind of Object the data item is, otherwise the
error could not report it.

Any ideas? Thanks!

 

[Guest]

Jed, dumb question: in your one that works, you use "ClientName", but in the
ones that don't you use "ClientContact". Is that right?

Bill

 

[Guest]

Unfortunately, no.

It is a good catch though. I noticed that after I posted. Both ClientName
and ClientContact are legitimate string properties of the object. I get the
same behaviour with both.

Thanks!

 

[Matt Berther]

Hello Jed,

Because objects serialized from web services do not contain public properties,
they contain public fields. Fields are not able to be used for declarative
data binding.

The reason it works in your code-behind, is because you are referencing a
field, which is valid in code.

 

[Guest]

Thanks, Matt,

Huh. I will look into that. I didn't know that there was even a "Field"
concept for class objects, nor do I even now understand how the Framework
maps my Property to this virtual "Field" value/construct.

Is there a best practices on how to overcome this (i.e.,custom
deserializer)? or is just impossible when working with web services?

Thanks again,
Jeff

 

[Matt Berther]

Hello Jed,

The differences between fields and properties are:

class Foo
{
public string Foo; // this is a field

private string bar;
public string Bar // this is a property
{
get { return bar; }
set { bar = value; }
}
}

According to this article [1] allowing databinding to fields is not something
thats going to change...

[1]http://www.nikhilk.net/Entry.aspx?id=42

Now, from what I've seen of ASP.NET 2.0, the class generated from the WSDL
has get/set properties instead of fields, so this might be good news for you.

Other than that, I imagine you could probably avoid using the web reference
and craft your communication layer yourself and get around this...

 

[fd537]

Hi,

I was searching the internet to find out how to bind the selected
columns of an array of custom objects to the datagrid and i found this
post on google groups. I want you to please have a look at my sample
code and let me know if i am on the right track or not. I am new to
..net and would like to have some guidance from u guys. here is what
iam trying to do:

1) get an array of objects from the web service method(for ex: lets
say there are 4 fields/properties for each object)
2) i want to bind only 2 fields/properties to the datagrid.
3) i have written an event handler that assigns the value of the
property to the literal control inside a datagrid's item template
column.
4) attached the event handler to the datagrid by using the
OnItemDataBound event of the datagrid


here is the code that i have:

event handler for the OnItemDataBound event :

public void Item_Bound(object sender, DataGridItemEventArgs e)
{
if(e.Item.ItemType == ListItemType.Item || e.Item.ItemType ==
ListItemType.AlternatingItem)
{
Literal l = (Literal)e.Item.FindControl("lit");
if(l.Text == String.Empty)
{
l.Text = ((FormsOrderingWS.Order)
e.Item.DataItem).OrderDate.ToString();
}
}
}





HTML code for datagrid:

<aspataGrid OnItemDataBound="Item_Bound"......>
<asp:Columns>
<asp:TemplateColumn HeaderText="Order Date">
<ItemTemplate>
<asp:Literal ID="lit" Runat="server"></asp:Literal>
</ItemTemplate>
</asp:TemplateColumn>
</asp:Columns>
</aspataGrid>


please suggest changes if iam wrong. Thank you