Object reference not set to an instance of an object in Telerik.Web.UI.RadComboBox.OnInit

DESCRIPTION

Object reference not set to an instance of an object in Telerik.Web.UI.RadComboBox.OnInit(EventArgs e)

In some cases, after a few postbacks, you may get a similar error.

This error seems related to the pager of the grid, yet we have not received a sample that reproduces the error so that we can investigate.

Object reference not set to an instance of an object.    
at Telerik.Web.UI.RadComboBox.OnInit(EventArgs e)    
at System.Web.UI.Control.InitRecursive(Control namingContainer)    
at System.Web.UI.Control.AddedControl(Control control, Int32 index)    
at Telerik.Web.UI.GridPagerButtonBuilder.CreatePageSizeDropDown(Panel container)    
at Telerik.Web.UI.GridPagerItem.InitializePagerItem(GridColumn[] columns)    
at Telerik.Web.UI.GridPagerItem.SetupItem(Boolean dataBind, Object dataItem, GridColumn[] columns, ControlCollection rows)    
at Telerik.Web.UI.GridTableView.CreateTopPagerItem(Boolean useDataSource, GridColumn[] copiedColumnSet, Boolean isPagingEnabled, GridTHead thead)    
at Telerik.Web.UI.GridTableView.CreateControlHierarchy(Boolean useDataSource)    
at Telerik.Web.UI.GridTableView.CreateChildControls(IEnumerable dataSource, Boolean useDataSource)    
at System.Web.UI.WebControls.CompositeDataBoundControl.CreateChildControls()    
at System.Web.UI.Control.EnsureChildControls()    
at Telerik.Web.UI.GridTableViewBase.get_Controls()    
at Telerik.Web.UI.GridTableView.GetGridTable()    
at Telerik.Web.UI.RadGrid.PrepareRowsVisibility(GridTableView view)    
at Telerik.Web.UI.RadGrid.PrepareItems()    
at Telerik.Web.UI.RadGrid.ControlPreRender()    
at System.Web.UI.Control.PreRenderRecursiveInternal()    
at System.Web.UI.Control.PreRenderRecursiveInternal()    
at System.Web.UI.Control.PreRenderRecursiveInternal()    
at System.Web.UI.Control.PreRenderRecursiveInternal()    
at System.Web.UI.Control.PreRenderRecursiveInternal()    
at System.Web.UI.Control.PreRenderRecursiveInternal()    
at System.Web.UI.Control.PreRenderRecursiveInternal()    
at System.Web.UI.Control.PreRenderRecursiveInternal()    
at System.Web.UI.Control.PreRenderRecursiveInternal()    
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

SOLUTION

The solutions below are suggestions that have been helpful in various cases, so you can try them:

• Make sure the grid is not bound to a null(Nothing) data source. If the there is no data to bind to the grid, use an empty string instead: RadGrid1.DataSource = "";
• Make sure that the grid data source is set only in the NeedDataSource handler, and that there are no calls to its .DataBind() method (replace them with .Rebind()). You can read more on how to configure advanced data binding in the following article: Programmatic Data Binding Using the NeedDataSource Event.
• If the data is a small amount,** disable paging** in the grid.
• Use a RadDropDownList instead of a ComboBox in the pager of the grid

<MasterTableView>
    <PagerStyle PageSizeControlType="RadDropDownList" />

• Make the pager always visible

<MasterTableView>
    <PagerStyle AlwaysVisible="true" />

• Try a pager mode without a dropdown, like NextPrev or Slider.

<MasterTableView>
    <PagerStyle Mode="Advanced|NextPrev|NextPrevNumericAndAdvanced|NumericPages|Slider" />

• If you are changing the structure of the grid (list of columns, for example), do that in Page_Init as explained in the following articles: Changing the Grid Structure Dynamically on Postback and Creating a RadGrid Programmatically. Do NOT do this in late events like PreRender.
• Remove RadCompression entries from your web.config. Having that can cause double compression of the ViewState and errors. IIS7 and later have their own dynamic content compression module which makes RadCompression redundant.
• If the grid is AJAX-enabled, remove nested RadAjaxPanel instances around it. In general, simplify the AJAX setup to avoid nested update panels or RadAjaxManager settings as well.