I have been working on a way to take a datatable from a dataset and
transform it into a Geography Markup Language(GML) stream so it can be
loaded into another component. The problem i'm finding is that the building
of the string to transform it into a stream is taking longer and longer as
you add more data to the string ( as you can see from the printout below.
Any suggestions for reducing the time? Should i be writing the GML to the
memory stream right away rather than trying to build one big string and
write that to memory stream? This data table that could be coming in could
contain thousands and thousands of rows.
----------------------------------------------------------------------------
-------------------
2007-07-20 11:50:17 AM : 100
2007-07-20 11:50:20 AM : 200
2007-07-20 11:50:23 AM : 300
2007-07-20 11:50:27 AM : 400
2007-07-20 11:50:32 AM : 500
2007-07-20 11:50:37 AM : 600
2007-07-20 11:50:43 AM : 700
2007-07-20 11:50:50 AM : 800
2007-07-20 11:50:59 AM : 900
2007-07-20 11:51:08 AM : 1000
2007-07-20 11:51:17 AM : 1100
2007-07-20 11:51:27 AM : 1200
2007-07-20 11:51:39 AM : 1300
-----------------------------------------------CODE
BELOW---------------------------------------------
Public Sub LoadDataTable(B yVal dt As DataTable, ByVal xcol As String,
ByVal ycol As String, ByVal srs As String)
Dim dr As DataRow
Dim dc As DataColumn
Dim GMLString As String
Dim featureID As Integer = 1
GMLString = SetGMLHeader()
For Each dr In dt.Rows
GMLString &= " <gml:featureMem ber>" & vbCrLf
GMLString &= " <SML:NavPoint fid=""NavPoint. " & featureID &
""">" & vbCrLf
GMLString &= ConvertRecord(d r, dt.Columns, xcol, ycol, srs)
GMLString &= " </SML:NavPoint>" & vbCrLf
GMLString &= " </gml:featureMemb er>" & vbCrLf
featureID += 1
If featureID Mod 100 = 0 Then
Console.WriteLi ne(Date.Now & " : " & featureID)
End If
Next
GMLString &= SetGMLFooter()
Dim memoryWriter As New StreamWriter(mG MLStream)
memoryWriter.Wr ite(GMLString)
memoryWriter.Fl ush()
'Console.WriteL ine(GMLString)
End Sub
Private Function SetGMLHeader() As String
Dim returnString As String
returnString = "<?xml version=""1.0"" encoding=""UTF-8""?>" & vbCrLf
& vbCrLf
returnString &= "<SML:FeatureCo llection " & vbCrLf
returnString &= " xmlns=""http://www.spatialmapp ing.com/gml""" &
vbCrLf
returnString &= " xmlns:gml=""htt p://www.opengis.net/gml""" & vbCrLf
returnString &= " xmlns:SML=""htt p://www.spatialmapp ing.com/gml""" &
vbCrLf
returnString &= "
xmlns:xsi=""htt p://www.w3.org/2001/XMLSchema-instance"">" & vbCrLf & vbCrLf
& vbCrLf
Return returnString
End Function
Private Function SetGMLFooter() As String
Dim returnString As String
returnString = "</SML:FeatureColl ection" & vbCrLf
Return returnString
End Function
Private Function ConvertRecord(B yVal geoRecord As DataRow, ByVal
geoColumns As DataColumnColle ction, ByVal xcol As String, ByVal ycol As
String, ByVal srs As String) As String
Dim returnString As String
For Each dc As DataColumn In geoColumns
If dc.ColumnName <xcol And dc.ColumnName <ycol Then
returnString &= " <SML:" & dc.ColumnName.T oUpper &
">"
returnString &= geoRecord.Item( dc.ColumnName)
returnString &= "</SML:" & dc.ColumnName.T oUpper & ">" &
vbCrLf
End If
Next
returnString &= " <SML:GEOMETRY >" & vbCrLf
returnString &= " <gml:Point srsName=""" & srs & """>"
& vbCrLf
returnString &= " <gml:coordinate s>" &
geoRecord.Item( xcol) & "," & geoRecord.Item( ycol) & "</gml:coordinates >" &
vbCrLf
returnString &= " </gml:Point>" & vbCrLf
returnString &= " </SML:GEOMETRY>" & vbCrLf
Return returnString
End Function
