Radcombox -There was error in callback

[Naga]

Dynamically created ComboBox and Load-on-demand not working .

[Shinu]

Hi Naga,

Please have a look into the following C# code snippet which works fine at my end.

C#:

protected void Page_Load(object sender, EventArgs e)
{
    Telerik.Web.UI.RadComboBox combo =new Telerik.Web.UI.RadComboBox();
    combo.ID = "RadComboBox1";
    combo.AutoPostBack = true;
    combo.EmptyMessage = "Select";
    combo.EnableLoadOnDemand = true;
    combo.ItemsRequested += new Telerik.Web.UI.RadComboBoxItemsRequestedEventHandler(combo_ItemsRequested);
    form1.Controls.Add(combo);
}
void combo_ItemsRequested(object sender, Telerik.Web.UI.RadComboBoxItemsRequestedEventArgs e)
{
    Telerik.Web.UI.RadComboBox combo = (Telerik.Web.UI.RadComboBox)sender;
    String connstring = WebConfigurationManager.ConnectionStrings["NorthwindConnectionString"].ConnectionString;
    SqlConnection conn = new SqlConnection(connstring);
    SqlDataAdapter adapter = new SqlDataAdapter();
    adapter.SelectCommand = new SqlCommand("SELECT Cityname from City ", conn);
    DataTable data = new DataTable();
    conn.Open();
    try
    {
        adapter.Fill(data);
        combo.DataSource = data;
        combo.DataTextField = "Cityname";
        combo.DataBind();
    }
    finally
    {
        conn.Close();
    }
}

Let me know if you have any concern.
Thanks,
Shinu.

[Naga]

Static radcombox load on demand is working fine,Dynamic Rad combobox load on demand not working.
We are using telerik(2013.3.1114.45)version in visual studio 2012.

Dynamic Rad combobox load on demand time,Iam getting "There was error in callback" this error.

[Shinu]

Hi Naga,

Please have a look into the following forum thread which deals the same issue. Please provide your code if it doesn't help.

Load On Demand and Exception handling.
Server Error in the ItemRequest Event.

Thanks,
Shinu.

[Naga]

Hi Shinu,



          Please check error .verify the below mentioned code also.

public void InstantiateIn(System.Web.UI.Control container)
            {

                combo = new RadComboBox();
                combo.ID = colname;

                combo.AutoPostBack = true;
                combo.AppendDataBoundItems = true;
                combo.AllowCustomText = true;
                combo.CheckBoxes = true;
                combo.AutoPostBack = true;
                combo.EnableCheckAllItemsCheckBox = true;

                combo.CheckedItemsTexts = RadComboBoxCheckedItemsTexts.DisplayAllInInput;
                combo.MarkFirstMatch = true;
                combo.HighlightTemplatedItems = true;
                combo.EmptyMessage = "All";
                combo.NoWrap = false;
                combo.CssClass = "target-users-popup-dropdown";
                combo.DropDownCssClass = "target-users-popup-dropdown-1";
                combo.Localization.AllItemsCheckedString = "All";
                combo.Localization.CheckAllString = "All";
                combo.OnClientDropDownClosing = "ShowModalPopup";
                combo.PreRender += new EventHandler(combo_PreRender);
                combo.EnableLoadOnDemand = true;
               combo.ShowMoreResultsBox = true;
                 combo.ItemsPerRequest=10;
                 combo.EnableVirtualScrolling = true;
                combo.SelectedIndexChanged += new RadComboBoxSelectedIndexChangedEventHandler(l_SelectedIndexChanged);
                combo.ItemDataBound += new RadComboBoxItemEventHandler(combo_ItemDataBound);
               combo.ItemsRequested += new RadComboBoxItemsRequestedEventHandler(combo_ItemsRequested);
                combo.DataValueField = colname;
                combo.DataTextField = colname;
                combo.DataBind();
                container.Controls.Add(combo);

            }

            void combo_ItemsRequested(object sender, RadComboBoxItemsRequestedEventArgs e)
            {
                int ItemsPerRequest = 10;

                RadComboBox combo = (RadComboBox)sender;
                if (combo != null)
                {

                    int itemOffset = e.NumberOfItems;
             );
                    List<string> data = GetUserProfieColumnData(combo.DataValueField, itemOffset, ItemsPerRequest);

                    e.EndOfItems = ItemsPerRequest > data.Count;

                    for (int i = 0; i < data.Count; i++)
                    {
                                        combo.Items.Add(new RadComboBoxItem(data[i].ToString(), data[i].ToString()));

                    }

                  
                    obj.ComboPrerender(sender, e);

                }
            }

[Shinu]

Hi  Naga,

Please try the following code snippet which works fine at my end.

C#:

protected void Page_Load(object sender, EventArgs e)
{
    Telerik.Web.UI.RadComboBox combo;
    string colname = "CompanyName";
    combo = new RadComboBox();
    combo.ID = colname;

    combo.AutoPostBack = true;
    combo.AppendDataBoundItems = true;
    combo.AllowCustomText = true;
    combo.CheckBoxes = true;
    combo.AutoPostBack = true;
    combo.EnableCheckAllItemsCheckBox = true;

    combo.CheckedItemsTexts = RadComboBoxCheckedItemsTexts.DisplayAllInInput;
    combo.MarkFirstMatch = true;
    combo.HighlightTemplatedItems = true;
    combo.EmptyMessage = "All";
    combo.NoWrap = false;
    combo.CssClass = "target-users-popup-dropdown";
    combo.DropDownCssClass = "target-users-popup-dropdown-1";
    combo.Localization.AllItemsCheckedString = "All";
    combo.Localization.CheckAllString = "All";
    combo.EnableLoadOnDemand = true;
    combo.ShowMoreResultsBox = true;
    combo.ItemsPerRequest = 10;
    combo.EnableVirtualScrolling = true;
    combo.ItemsRequested += new RadComboBoxItemsRequestedEventHandler(combo_ItemsRequested);
    combo.DataValueField = colname;
    combo.DataTextField = colname;
    combo.DataBind();
    form1.Controls.Add(combo);
}
void combo_ItemsRequested(object sender, RadComboBoxItemsRequestedEventArgs e)
{
    RadComboBox combo = (RadComboBox)sender;
    DataTable data = GetData(e.Text);
    int itemOffset = e.NumberOfItems;
    int endOffset = Math.Min(itemOffset + ItemsPerRequest, data.Rows.Count);
    e.EndOfItems = endOffset == data.Rows.Count;

    for (int i = itemOffset; i < endOffset; i++)
    {
        combo.Items.Add(new RadComboBoxItem(data.Rows[i]["CompanyName"].ToString(), data.Rows[i]["CompanyName"].ToString()));
    }
    e.Message = GetStatusMessage(endOffset, data.Rows.Count);
}
private static DataTable GetData(string text)
{
    SqlDataAdapter adapter = new SqlDataAdapter("SELECT * from Customers ", ConfigurationManager.ConnectionStrings["NorthwindConnectionString"].ConnectionString);
    DataTable data = new DataTable();
    adapter.Fill(data);
    return data;
}
private static string GetStatusMessage(int offset, int total)
{
    if (total <= 0)
        return "No matches";
    return String.Format("Items <b>1</b>-<b>{0}</b> out of <b>{1}</b>", offset, total);
}

Hope this will helps you.
Thanks,
Shinu.

[Naga]

What is the difference in code?

[Shinu]

Hi Naga,

In my code OnItemRequestedEvent I am trying to access all the data from the table and adding items to the RadComboBox based on the current itemoffset and endoffset values. So first it will add only 10 items to the RadComboBox and then from 10 to 20 items and so on. The GetStatusMessage is used to display the status of the RadComboBoxItems.

Thanks,
Shinu.