CheckedItems.Count Always Returns a Value of Zero (0)

[Brian]

I created a .NET page using the demo ComboBox-CheckBoxes (http://demos.telerik.com/aspnet-ajax/combobox/examples/functionality/checkboxes/defaultcs.aspx) as a guide. All worked great.

 

Then I added an asp:SqlDataSource to my page with ID="sdsEmailAddresses". I went to the telerik:RadComboBox and set DataSourceID="sdsEmailAddresses" (along with other data source settings). The combobox displayed the desired data and when you selected items in the list and click a button, the click event has the following, which successfully detects the number of items that where selected:

if (this.cmbTO.CheckedItems.Count != 0) {

//do something

}

But I need to use a complex Select Command that needs to be filtered on-the-fly. So instead of using the asp:SqlDataSource, I have a method that sets the radcombobox like the following:

 

this.cmbTO.DataTextField = "UserName";

this.cmbTO.DataValueField = "UserEmail";

this.cmbTO.DataSource = dtTbl;

this.cmbTO.DataBind();

This code properly populates radcombobox, but after making combo selections, and clicking the button, the Count always returns zero.

 

What's up with that?

[Princy]

Hello Brian,

I am able to replicate your issue by enabling load on demand and hence I believe you are using EnableLoadOnDemand property of the RadComboBox. RadComboBox items are not accessible on the server-side when loading them on demand and therefore always return CheckedItems as well as SelectedItems count as zero and this is a known issue. This is because RadComboBox items loaded on demand using the ItemsRequested event handler or WebService do not exist on the server and cannot be accessed using the server-side FindItemByText / Value methods. SelectedItem and SelectedIndex properties are always Null / Nothing. This is needed for speed (otherwise the combobox will not be that responsive upon each keypress if state information and ViewState were persisted).

Please have a look at the following code without using load on demand which works fine at my end.

ASPX:

<telerik:RadComboBox runat="server" ID="RadComboBox1" CheckBoxes="true">
</telerik:RadComboBox>
<br />
<br />
<telerik:RadButton ID="RadButton1" runat="server" Text="Get Count" OnClick="RadButton1_Click">
</telerik:RadButton>

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        populateRadCombobox("select ContactName from Customers");
    }
}
protected void populateRadCombobox(string query)
{
    String ConnString = ConfigurationManager.ConnectionStrings["NorthwindConnectionString"].ConnectionString;
    SqlConnection conn = new SqlConnection(ConnString);
    SqlDataAdapter adapter = new SqlDataAdapter();
    adapter.SelectCommand = new SqlCommand(query, conn);

    DataTable myDataTable = new DataTable();

    conn.Open();
    try
    {
        adapter.Fill(myDataTable);
        RadComboBox1.DataTextField = "ContactName";
        RadComboBox1.DataSource = myDataTable;
        RadComboBox1.DataBind();
    }
    finally
    {
        conn.Close();
    }
}
protected void RadButton1_Click(object sender, EventArgs e)
{
    if (RadComboBox1.CheckedItems.Count > 0)
    {
        //business logic goes here
    }
    else
    {

    }
}

Thanks,
Princy.

[Brian]

Hi Princy,

 

Thank you for your quick reply.

 

Prior to posting this issue yesterday, I had already read a Telerik document concerning the use of EnableLoadOnDemand property and the ItemsRequested event with regards to RadCombos and server-side access. I had applied the info in that document, but it was not resolving this issue. So I removed all of those changes that I made to my page, including the removal of the EnableLoadOnDemand property. After some frustrations, I then posted this issue.

 

When I reviewed what you had posted, I found that your example was almost exactly like mine, with one difference. You had populateRadCombobox inside of an if (!IsPostBack) statement, and I did not. If you place your call to populateRadCombobox outside of the if (!IsPostBack), you will find that this also causes CheckedItems.Count property to always return a zero.

 

In the past, I’ve used if (!IsPostBack) in the Page_Load event more times than I care to admit; it was an oversight in this case. So even without the use of EnableLoadOnDemand, you can repro this problem if you place populateRadCombobox outside of the if (!IsPostBack).

 

I wonder though; shouldn’t the postback have caused all the items that had a checkmark to become unchecked during the postback? That’s what was driving me crazy; everything I had checked was still checked after I clicked my button, yet the CheckedItems.Count would return a zero.

 

Issue resolved,

Thank you

[Marie]

I'm having the same problem. I'm using EnableLoadOnDemand="True" because I need to have Autocomplete combobox.
I don't want to load everything on load page because I have the long long lists coming from an old server Informix. I need speed and for that I use EnableLoadOnDemand and CheckBoxes="true". for that I use OnItemsRequested
There is another way to do that?
I tried to add to this OnItemChecked but I have another error :

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

If I use SelectedIndexChanged with my autocomplete and loadondemand I have the same problem mentionned here. Only after the second check works. If I check only one doesn't work...

Any suggestion?
Thanks

[Nencho]

Hello,

@Brian, indeed the cause of the experienced issue is the fact, that each time the Page_Load event is hit, you are repopulating the control with data. Thus, the selection, along with the client-state of the RadComboBox is lost and the Checked Items count is zero. I would suggest you to encapsulate the population with data, within the If(!IsPostBack) statement, in order to persist the correct behavior.

@Marie, as previously mentioned by Princy, the LoadOnDemand mechanism is not supported along with the CheckBoxes usage. This is described in our help article bellow:

http://www.telerik.com/help/aspnet-ajax/combobox-usability-checkboxes.html

However, another possible implementation might be helpful for your scenario. You could still use LoadOnDemand mechanism of the RadComboBox and place a checkbox in the ItemTemplate of the control. Please refer to the following forum thread, where this subject is discussed in details and a sample project is provided:

http://www.telerik.com/forums/radcombo-multi-select-and-load-on-demand

Regards,
Nencho
Telerik

 

 

[Dan]

Hi I removed the LoadOnDemand and it still returns 0 on count

[Nencho]

Hello Dan,

Since I am not able to locally replicate the issue in question in this thread, when the LoadOnDemand feature is disabled, and as I can see you have already submitted a support ticket on the matter - I would suggest you to continue the correspondence in the support ticket.

Regards,
Nencho
Telerik