July 30, 2008

Mapguide 2009 / OS 2.0 Get Selected Key Values VB.NET Example and the dreaded MgSelection.GenerateFilter Issue

Filed under: Mapguide — Tags: , — Darrin Maidlow @ 2:12 am

Tonight I came across the .  I had read about it, and made a mental note that one day it would be an issue.  That note wasn’t very good, and I completely forgot about it.   I was wrapping up the updates around the report this eve and fortunately I bothered to select the entire map and run through a report.

RADE Report - but what, only 20 records returned?

Report looked good.  The results were sorting, checkboxes working.   Wait a minute, I selected the entire map.  There should be more than twenty items returned.  So a quick search of my twelve thousand saved e-mails from the turned up what needed to be done.  Fortunately Autodesk added a GenerateFilters call to MgSelection.  This call returns an MgStringCollection of filters.

Basically the solution to this problem is to use GenerateFilters instead of GenerateFilter, and loop through the results.  Each time, appending the returned keys to the complete list.  For example:

   1: Public Shared Function GetSelectedKeysString(ByRef siteConn As MgSiteConnection, _
   2:     ByRef resSvc As MgResourceService, ByVal oMap As MgMap, ByVal SessionId As String, _
   3:     ByVal SelectionXML As String, ByVal layerResID As MgResourceIdentifier, _
   4:     ByVal keyFieldName As String) As String
   6:     Dim szKeys As String = ""
   7:     Dim oSel As New MgSelection(oMap)
   8:     oSel.FromXml(SelectionXML)
   9:     Dim curLay As MgLayerBase
  10:     'isolate the layer
  11:     For Each layerItem As MgLayerBase In oSel.GetLayers
  12:         If layerItem.Name = layerResID.Name Then
  13:             curLay = layerItem
  14:         End If
  15:     Next
  17:     Dim featSvc As MgFeatureService = siteConn.CreateService(MgServiceType.FeatureService)
  18:     Dim queryOptions As New MgFeatureQueryOptions
  19:     Dim featureClassName As String = curLay.GetFeatureClassName
  20:     'workaround using GenerateFilters and looping through the results as needed
  21:     Dim featureReader As MgFeatureReader
  22:     Dim filters As MgStringCollection = oSel.GenerateFilters(curLay, featureClassName, 20)
  23:     Dim filterCnt As Integer = 0
  24:     While filterCnt < filters.GetCount
  25:         queryOptions.SetFilter(filters.GetItem(filterCnt))
  26:         featureReader = featSvc.SelectFeatures(New MgResourceIdentifier(curLay.GetFeatureSourceId), featureClassName, queryOptions)
  27:         While featureReader.ReadNext
  28:             If szKeys = "" Then
  29:                 szKeys = ConvertPropertyToString(featureReader, keyFieldName)
  30:             Else
  31:                 szKeys &= "," & ConvertPropertyToString(featureReader, keyFieldName)
  32:             End If
  33:         End While
  34:         featureReader.Close()
  35:         featureReader.Dispose()
  36:         filterCnt += 1
  37:     End While
  38:     Return szKeys
  39: End Function


In this code, we get the selection from the MgMap object and then isolate the layer in question.  Then we generate the collection of filters and loop through them.  Each time, adding the appropriate value to the list of keys.  Note the use of ConverPropertyToString, this needs to be used to ensure that the various data types are converted over to string.

I’ve included this function as well as a couple other handy related ones in the attached zip file

.  If you’re looking for a C# example of how to use GenerateFilters one is provided in the .

After making these changes my reports now look all proper! hurray.  Maybe I can hit the sack now?  nahh.

RADE report - but this time everything looks ok 

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