All,

I have written a very simple custom composite control that includes a
control of type System.Web.UI.WebControls.Table.

The control renders fine in run time, but for some reason, it does not
render properly in design time.

In design time it renders something like this:

[TestTableControl "TestTableControl1"]


Could someone please explain why this control does not render in
design time.
(complete code is included below)

Thanks in advance!!!

--Jonathan

------------------------------------------------------------------------------


using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using System.Collections;


namespace StyleLibFunctions
{
#region TestTableControl

[ToolboxData("<{0}:TestTableControl
runat=server></{0}:TestTableControl>")]
public class TestTableControl: WebControl
{
#region Variable Declaration

private Table _table;
private TableRow _tr;
private TableCell _td;

#endregion Variable Declaration

#region Overridden Properties
public override ControlCollection Controls
{
get
{
EnsureChildControls();
return base.Controls;
}
}
#endregion Overridden Properties

#region Overridden Methods
protected override void CreateChildControls ()
{
//clear controls
Controls.Clear();

//Create a Table object
_table = new Table();
_tr = new TableRow();
_td = new TableCell();
_td.Controls.Add(new LiteralControl("Cell Content"));

_tr.Cells.Add(_td);
_table.Rows.Add(_tr);

//add table to control tree
Controls.Add (_table);

}
protected override void Render(HtmlTextWriter writer)
{
_table.RenderControl(writer);
}
#endregion Overridden Methods
}
#endregion

Hi,

you should implement composite control designer for the control and also
generally implement INamingCotainer interface in the control.

About designer implementation:

a) Override Controls accessor to call EnsureChildControls before returning
base class implementation (You have done this already)
b) Write the designer and apply it for the control. Base logic is to call
Control's (it is Component for the designer) Controls accessor to make sure
child controls are created at the time when Control is rendered. This is
done in overridden GetDesignTimeHtml method. In overridden Initialize method
we just check that Control fulfills certain requirements. (You can also make
the designer general by removing type checkings)

Example:

using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using System.Collections;
using System.Web.UI.Design;

namespace StyleLibFunctions
{
#region TestTableControl
[ToolboxData("<{0}:TestTableControl
runat=server></{0}:TestTableControl>"),Designer(typeof(TestTableCompositeDes
igner))
]
public class TestTableControl: WebControl, INamingContainer
{
#region Variable Declaration
private Table _table;
private TableRow _tr;
private TableCell _td;
#endregion Variable Declaration
#region Overridden Properties
public override ControlCollection Controls
{
get
{
EnsureChildControls();
return base.Controls;
}
}
#endregion Overridden Properties
#region Overridden Methods
protected override void CreateChildControls ()
{
//clear controls
Controls.Clear();
//Create a Table object
_table = new Table();
_tr = new TableRow();
_td = new TableCell();
_td.Controls.Add(new LiteralControl("Cell Content"));
_tr.Cells.Add(_td);
_table.Rows.Add(_tr);
//add table to control tree
Controls.Add (_table);
}
protected override void Render(HtmlTextWriter writer)
{
_table.RenderControl(writer);
}
#endregion Overridden Methods
}
#endregion
public class TestTableCompositeDesigner : ControlDesigner
{
public override void Initialize(IComponent component)
{
if(!(component is INamingContainer) && !(component is TestTableControl))
{
throw new ArgumentException("Component must be a TestTableControl and
implement INamingContainer interface","component");
}
base.Initialize (component);
}
public override string GetDesignTimeHtml()
{
ControlCollection controls=((Control)Component).Controls;
return base.GetDesignTimeHtml ();
}
}
}

--
Teemu Keiski
MCP,Designer/Developer
Mansoft tietotekniikka Oy
http://www.mansoft.fi

ASP.NET Forums Moderator, www.asp.net
AspAlliance Columnist, www.aspalliance.com

Email:
joteke@aspalliance.com

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