Server Control using a Collection

[ME]

Ok I am brand new at C#. I am attempting to build a server control that
contains a collection. Trouble is when I place my control on my page and
edit the collection via the property window (using an Editor) the control
generates the following html:

<controlgroup:ControlGroupControl id="ControlGroupControl2" runat="server"
Items="(Collection)"></controlgroup:ControlGroupControl>

Note that Items shows up as just "(Collections)". Now the desired tag
structure is similar to the following:

<aspropDownList id="DropDownList1" runat="server">
<asp:ListItem Value="3333">3333</asp:ListItem>
<asp:ListItem Value="ffffffffff">ffffffff</asp:ListItem>
</aspropDownList>

So now how would one go about creating a control to automatically generate
the correct tags and also read from them as well?

Thanks,

Matt

 

[Teemu Keiski]

Hi,

1) the collection property needs to be read-only (instantiate the collection
when property is accessed for the first time)
2). collection property should be declared with
PersistenceMode(PersistenceMode.InnerProperty),
DesignerSerializationVisibility(DesignerSerializationVisibility.Content) and
NotifyParentProperty(true) attributes

Have you done these? If this doesn't help, post the code.

 

[ME]

Thank you. What would it take to get the control to "read" these values
after the GUI page has been saved and closed then reopened again? It seems
that if I do this the control reverts to "Error Creating Control". My guess
is that it is not reading these values but I am not absolutly certain.
Below is my controls code (please excuse my ignorance, like I said I am very
new to this!):


using System;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.Design;

using System.ComponentModel;

using System.ComponentModel.Design;

using System.Collections;

using System.IO;

using System.Text;

using System.Drawing.Design;

//using System.

[

assembly: TagPrefix("ControlGroup","ControlGroup")

]

namespace ControlGroup

{

/// <summary>

/// Summary description for WebCustomControl1.

/// </summary>

///

[DefaultProperty("Text"),

ToolboxData("<{0}:ControlGroupControl
runat=server></{0}:ControlGroupControl>"),

SerializableAttribute()]

public class ControlGroupControl : System.Web.UI.WebControls.WebControl,
INamingContainer

{

#region Private Variables

private string text="";

private ControlGroupItemCollection items = new ControlGroupItemCollection();

private ControlGroupItemCollection allItems = new
ControlGroupItemCollection();

private ListBox lbItems = new ListBox();

private Label lblTitleID = new Label();

private TextBox txtInfo = new TextBox();

#endregion

#region Constructors and Initializers

public ControlGroupControl()

{

try

{

this.Visible=true;

txtInfo.Height=300;

//this.Height=100;

//this.Width=100;

lbItems.BorderStyle=BorderStyle.None;

lbItems.BorderWidth=0;

lbItems.Width=300;

txtInfo.Width=300;

txtInfo.TextMode=TextBoxMode.MultiLine;

txtInfo.Text += "CONSTRUCTED!\n";

}

catch (Exception ex)

{

items=null;

allItems=null;

text="Error! - " + ex.ToString();

}

}

protected override void OnInit(EventArgs e)

{

if (AllItems.Count != Page.Controls.Count-1)

{

txtInfo.Text += "INITIALIZED & RESET!\n";

fillAllItems();

}

base.OnInit (e);

}

protected override void OnLoad(EventArgs e)

{

txtInfo.Text += "LOADED!\n";

base.OnLoad (e);

}

protected override void OnPreRender(EventArgs e)

{

txtInfo.Text += "PRE-RENDER!\n";

base.OnPreRender (e);

}



#endregion

#region Void Methods

private void FillListBox()

{

//Start by clearing the list

lbItems.Items.Clear();

//If the items collection has not been instantiated then

//Do not attempt to iterate through it.

if (items.Count>0)

{

//for (int i=0; i< items.Count; i++)

foreach(ControlGroupItem cntl in items)

{

lbItems.Items.Add(cntl.ControlID.ToString());

}

}

else

{

//Writes "No Controls

lbItems.Items.Add("No Controls");

}



}

private void fillAllItems()

{

try

{

int c = Page.Controls.Count;

int tmpID=0;

ControlGroupItem tempControl = new ControlGroupItem();

allItems.Clear();


for(int i=0; i < c; i++)

{

//txtInfo.Text = txtInfo.Text + Page.Controls.ID.ToString() + "\n";

tempControl = new ControlGroupItem();

// set the control structure properties of the control

tempControl.ControlID = Page.Controls.ID.ToString();

tempControl.ControlType = Page.Controls.GetType();

//tempControl.BoundProperty=

// add the control structure to the collection

tmpID=this.allItems.Add(tempControl);

txtInfo.Text +="CONTROL " + this.allItems[tmpID].ControlID.ToString() + " ["
+ allItems.Count.ToString() + "]\n";

}

this.Text="WORKED!";

}

catch (Exception ex)

{

System.Diagnostics.Debug.Write(ex.ToString());

this.Text=ex.ToString();

}

}

#endregion


#region Properties

[

Bindable(true),

Category("Data"),

]

public string Text

{

get

{

return text;

}

set

{

text=value;

}

}



/// <summary>

/// Items = The group of referenced controls

/// </summary>

[Category("Misc"),

PersistenceMode(PersistenceMode.InnerProperty),

DesignerSerializationVisibility(DesignerSerializationVisibility.Content),

NotifyParentProperty(true),

EditorAttribute(typeof(ControlGroupEditor), typeof(UITypeEditor))

]

public ControlGroupItemCollection Items

{

get

{

return items;

}

}

[BrowsableAttribute (false)]

public ControlGroupItemCollection AllItems

{

get

{

return allItems;

}

set

{

allItems = value;

}

}

#endregion

#region Rendering

protected override StateBag ViewState

{

get

{

return base.ViewState;

}

}

protected override object SaveViewState()

{

return base.SaveViewState ();

}

protected override void LoadViewState(object savedState)

{

base.LoadViewState (savedState);

}



protected override void RenderContents(HtmlTextWriter writer)

{

//Render(writer);

base.RenderContents (writer);

}



protected override void RenderChildren(HtmlTextWriter writer)

{

FillListBox();

lblTitleID.Text=this.ID.ToString();

// Render

lblTitleID.RenderControl(writer);

writer.Write("<BR>");

lbItems.RenderControl(writer);

writer.Write("<BR>");

txtInfo.RenderControl(writer);

}

#endregion

}

}