Category Archives: VB.NET

(Possible) solution for MSChart ArgumentException The image is not found error

If you’re using Microsoft’s .NET charting control on your ASP.NET pages you may receive an annoying error

[ArgumentException]: The image is not found. at
System.Web.UI.DataVisualization.Charting.ChartHttpHandler.ProcessSavedChartImage(HttpContext context) at
System.Web.UI.DataVisualization.Charting.ChartHttpHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext context) at
System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

I could be intermittent, sometimes happen, sometimes not. In your web.config you already set your temp images to be stored as files and not deleted after serving:

<add key="ChartImageHandler" value="storage=file;timeout=20;url=~/temp/;deleteAfterServicing=false" />

as well as trying other remedies and nothing helps.

One possible solution is, while still using file temp storage, instead of indicating relative path via url property set it to absolute path via dir property:

<add key="ChartImageHandler" value="storage=file;timeout=20;dir=C:\TEMP;deleteAfterServicing=false" />

In the example above C:\TEMP is an absolute path to the temp folder on the Web Server. In your case it could be different; in multi-server (WebFarm) environment it should be a network share, accessible by all servers.

Select Distinct DataRows from ADO.NET DataTable using LINQ

If you’re trying to retrieve distinct rows from your ADO.NET data table using code like

From oRow As DataRow In dtTable.Rows Select oRow Distinct

or

(From oRow As DataRow In dtTable.Rows Select oRow).Distinct()

You may find that rows that are being return are not unique. That’s because by default LINQ compares table rows by reference. If you need to compare by actual values – use DataRowComparer in Distinct method call:

(From oRow As DataRow In dtTable.Rows Select oRow).Distinct(DataRowComparer.Default)

‘this.Column.Band’ is null or not an object error in UltraWebGrid filtering

When you filter Infragistics UltraWebGrid by clicking Filter icon in the column header – dropdown with filter values appears. Normally if you click elsewhere on the page – dropdown disappears. But sometimes it doesn’t, for example if you click an element that invokes a JavaScript function. Filter dropdown stays open and this could cause problems – when grid refreshes (and possibly other actions are performed) error is thrown:

‘this.Column.Band’ is null or not an object

The solution to this is to close filter dropdown ourselves. Put these lines into your client-side code whenever clicking outside the filter doesn’t close it:

var aGridCols = igtbl_getGridById('xMyGrid').Bands[0].Columns
   for (var I = 0; I < aGridCols.length; I++)
      aGridCols[I].showFilterDropDown(false);

Here we’re looping thru grids column collection (This example assumes grid is in Flat or OutlookGroupBy mode, if your grid is hierarchical, you will have to loop thru band collection as well). For every column we pass False to showFilterDropDown method which (probably showing Infragistics cute sense of humor) hides filter dropdown if it is open. If dropdown is hidden for the column already – nothing happens.

As a result opened filter dropdown is now always closed prior to previously offending action and the error doesn’t happen.

Speed up UltraWebGrid rendering on rebind

If you’re using Infragistics UltraWebGrid with it’s property Browser="Xml", you may find yourself living in a shotgun shack in a strange situation: When grid is rebinding – it takes (comparatively) short time to do server-side processing and then a very long time to render grid in the browser.

In my case it was most felt when grid (which had ViewType="OutlookGroupBy") was initially grouped with a lot of data in each group and then ungrouped back into flat view when user dragged last group column out. Using IE9 built-in developer tools I ran JavaScript profiler I found that culprit was Infragistics JS function “disposeNode” which was called numerous times and had worst both inclusive and exclusive execution time. Continue reading →

SSRS viewer doesn’t work on IIS7 64bit

If you’re developing an ASP.NET application that utilizes Microsoft’s SSRS ReportViewer control, you may experience a weird behavior while trying to use it on 64 bit version of IIS7 (Windows Server 2008 or Windows 7) – nothing is displayed in the main report area and even icons, such as Print, Export aren’t rendering.

One possible cause for this – your application is using Application Pool with 32bit mode enabled. If so – disable it or switch to a different application pool. Chances are this will fix the above issue.

WHDG: Correctly detect Async Callback

When using Infragistics WebHierarchicalDataGrid often there’s a need to detect grid’s async callback (for example we need to rebind the grid if it performs AJAX paging or expanding children). For flat WebDataGrid it was suggested to use grid’s RunBot.IsCallback property:

If xMyGrid.RunBot.IsCallback Then
   'Perform some operations for grid's async callback
End If

Now, WHDG also has RunBot.IsCallback property, but the above code always returns False for it. I know I’ve seen this before – a situation where a property doesn’t work on WHDG control itself, but works on the WHDG’s GridView object. Sensing a pattern I modified the code above for WHDG:

If xMyGrid.GridView.RunBot.IsCallback Then
   'Perform some operations for grid's async callback
End If

And bingo! Now Async callback is detected correctly.

UPDATE 4/27/2012: Turned out the above method doesn’t always work either. (To Infragistics stuff, if anybody happened to read this: The scenario above happens with WHDG in manual load on demand mode when grid’s RowIslandPopulating event is handled and ContainerGrid is created on demand and bound to data retrieved from the Database). The above method works when rows of the top level expanded (xMyGrid.GridView.RunBot.IsCallback is True) but fails if child rows are expanded to show grandchildren (in that case xMyGrid.GridView.RunBot.IsCallback is False).

We need another more reliable way to detect callback, no matter what caused it. And we can do that by checking HTTP Request. If it’s an Infragistics callback it will have a Form parameter with key like "__IGCallback************". So the code to always detect the callback correctly is:

If Request.Form.AllKeys.Any(Function(S As String) S IsNot Nothing AndAlso S.StartsWith("__IGCallback")) Then
   'Perform some operations for grid's async callback
End If

WebDataTree returns multiple selected nodes in single-select mode

This could be a bug in Infragistics WebDataTree control or it could be a very specific scenario (maybe it’s even by design, I don’t know) but here’s a weird behavior that I encountered. Using following code in WebDataTree’s event handler (oh and by the way, tree control is in a single-select mode):

Protected Sub xMyTree_SelectionChanged(ByVal sender As Object, ByVal e As NavigationControls.DataTreeSelectionEventArgs) Handles MyTree.SelectionChanged
   if e.NewSelectedNodes(0).Text = "Some Value"
      'do something with newly selected tree node
   end if
End Sub

I intended to use newly selected node to perform some operations. To my surprise e.NewSelectedNodes(0) referred to previously selected node (despite the name of the property) and newly selected value were located in e.NewSelectedNodes(1)! So the quick workaround was to use slightly modified code:

Protected Sub xMyTree_SelectionChanged(ByVal sender As Object, ByVal e As NavigationControls.DataTreeSelectionEventArgs) Handles MyTree.SelectionChanged
   if e.NewSelectedNodes(e.NewSelectedNodes.Count-1).Text = "Some Value"
      'do something with newly selected tree node
   end if
End Sub

This way it will always get latest selected node and the solution is universal. If the bug described above occurs – code will grab e.NewSelectedNodes(1) (because Count = 2). If the tree behaves as expected – code will get grab e.NewSelectedNodes(0) (because Count = 1)

Solution for WebHierarchicalDataGrid “DataKeyField is invalid” error

If you’re using Infragistics WebHierarchicalDataGrid and getting “DataKeyField is invalid” error after assigning DataKeyFields property for the root level:

xMyGrid.DataKeyFields = "[Key 1],[Key 2],[Key 3]"

and trying some data manipulation (like deleting rows, binding data etc.), try using GridView property of the grid instead:

xMyGrid.GridView.DataKeyFields = "[Key 1],[Key 2],[Key 3]"

The first method used to work, but somewhere around 2011 release of NetAdvantage it broke.

Remove namespaces from Xpath expression

If you ever need to remove namespaces from an XPath string, regex is a way to go. [\w]+:(?!:) expression to be precise. So if, for example your xpath is

Dim sXpath as String = "/ns1:ElementOne/ElementTwo/ns2:ElementThree"

this code

Regex.Replace(sXpath, "[\w]+:(?!:)", "")

will convert it into

/ElementOne/ElementTwo/ElementThree

Thanks Bogdan Emil Mariesan @ Stack Overflow for the solution