I have been developing in Microsoft .NET, using C# and managed and unmanaged C++. Is there any data provider for .NET that will allow me to work with spatial data? Are there any examples?

If not, can someone point me to the best examples for interacting with spatial data using C++?

I'm continuing my search, but thought you guys might be able to point me in a good direction quicker.

Thanks

Ron

Anyone got any pointers to useful OCCI and spatial examples?

I've been searching for .NET, I'll switch my searches to be for OCCI.

hi did sth like that:

  string constr = "User Id=scott;Password=tiger;Data Source=oracle";
  OracleConnection con = new OracleConnection(constr);
  con.Open();

  OracleCommand cmd = new OracleCommand("select * from cola_markets", con);
  cmd.XmlCommandType =  OracleXmlCommandType.Query;
  cmd.CommandText = query;
  cmd.BindByName = true;

  int rows = cmd.ExecuteNonQuery();

  XmlReader xmlReader =  cmd.ExecuteXmlReader();
  XmlDocument xmlDocument = new XmlDocument();
  xmlDocument.PreserveWhitespace = true;
  xmlDocument.Load(xmlReader);
  return xmlDocument;

and it returns sth like this:

<?xml version="1.0" encoding="utf-8"?>
<ROWSET>
  <ROW>
    <MKT_ID>1</MKT_ID>
    <NAME>cola_a</NAME>
    <SHAPE>
      <SDO_GTYPE>2003</SDO_GTYPE>
      <SDO_ELEM_INFO>
        <NUMBER>1</NUMBER>
        <NUMBER>1003</NUMBER>
        <NUMBER>3</NUMBER>
      </SDO_ELEM_INFO>
      <SDO_ORDINATES>
        <NUMBER>1</NUMBER>
        <NUMBER>1</NUMBER>
        <NUMBER>5</NUMBER>
        <NUMBER>7</NUMBER>
      </SDO_ORDINATES>
    </SHAPE>
  </ROW>
  <ROW>
    <MKT_ID>2</MKT_ID>
    <NAME>cola_b</NAME>
    <SHAPE>
      <SDO_GTYPE>2003</SDO_GTYPE>
      <SDO_ELEM_INFO>
        <NUMBER>1</NUMBER>
        <NUMBER>1003</NUMBER>
        <NUMBER>1</NUMBER>
      </SDO_ELEM_INFO>
      <SDO_ORDINATES>
        <NUMBER>5</NUMBER>
        <NUMBER>1</NUMBER>
        <NUMBER>8</NUMBER>
        <NUMBER>1</NUMBER>
        <NUMBER>8</NUMBER>
        <NUMBER>6</NUMBER>
        <NUMBER>5</NUMBER>
        <NUMBER>7</NUMBER>
        <NUMBER>5</NUMBER>
        <NUMBER>1</NUMBER>
      </SDO_ORDINATES>
    </SHAPE>
  </ROW>
...

but i have problems when i want to fill dataset with this data
oh, i wonder if sb have any experience in storing gml (geography markup language) in oracle db.

__
greetings
Bartosz Machocki

I have programmed OO4O in VB6 and it works quite well (read and write)
but the COM wrapper over the Oracle Objects is quite slow. I got some
very, very acceptable (read) performance by using OraCustomDynaset()
and breaking up the Sdo_Geometry into its constituent parts on the server
by doing the following:

select
a.shape.sdo_gtype,
a.shape.sdo_srid,
a.shape.sdo_elem_info,
a.shape.sdo_ordinates,.....
from <table> a

(With variations for SDO_POINT.)

Of course, this is not good if you want to do a SELECT ... FOR UPDATE.
Still, for fast read only access it is quite good.

Wrt access in ODP.NET I add in my vote for some decent support for
all Oracle Spatial vector objects in the ODP provider.

For those using 10g, instead of using the XML engine (nice approach)
you could use the TO_WKT() (returns CLOB) or TO_WKB() (returns BLOB)
and then process them accordingly in your .NET cient application (there are
some "GIS" development kits around - like TatukGIS's DK - that will map
WKT/WKB into Shapes (for shapefiles) etc.

For read only, you could push the conversions back into the database via materialized views with function based indexes eg

Create Materialized View WKT_VIEW
<mv properties>
AS
SELECT gid, a.geom.to_wkt()
FROM <my table> a;

Then create a function based index over the WKT/WKB column using an SDO_GEOMETRY constructor that takes the WKT/WKB and the SRID
as its elements.

In fact, you could simply store the WKT/WKB on the base table alongside the Sdo_Geometry and use triggers to keep them synchronised.

So, with WKT/WKB at 10g, you can do your insert,update as follows...

insert into <table> a set a.shape = MDSYS.SDO_GEOMETRY(:WKT, SRID);

Using WKT/WKB would give you maximum portability across SpatialDBs (eg MySQL, PostGIS etc) if this is what you are hoping to do in the future.

S.

Dan,

Now this is good news.

I know you can't let the cat out of the bag, but I do hope that the ODP.NET
stuff provides some good constructor and accessor functions for Sdo_Geometry
so we don't have to write our own! What I mean by this is that a programmer
shouldn't have to know the details of how the Sdo_Elem_Info array is organised
and interpreted, or how the ordinate array is arranged. This would make data
import/export so much easier.

It would also be nice if the ODP.NET API included some constructors/accessors
for WKB and WKT manipulations (other than having to have the server do the
computations via to_wkt()/from_wkt() etc.

S.

Hi Everyone,

If ODP.NET supports SDO_GEOMETRY object type mapping, what type(s) of the attributes in a corresponding C# or VB type/class do you perfer?

For example, if we use these instances with the System.Drawing.Drawing2D for vector graphic functionality, the ordinates attribute would be better represented as PathData instance, which encapsulates an array of points.

Or a vector of double will do for the ordinates attribute, as in JGeometry Java class?

Another issues is whether we should do safe type mapping to perserve data precision and null semantics of Oracle NUMBERs.

OracleDataAdapter Safe type mapping background info:

OracleDecimal Type and .NET Decimal Type:

OracleDecimal can store up to 38 precision, while the .NET Decimal datatype can only hold up to 28 precision. When accessing the OracleDecimal.Value property from an OracleDecimal that has a value greater than 28 precision, loss of precision can occur.
To retrieve the actual value of OracleDecimal, use the OracleDecimal.ToString() method.

If NUMBER is stored as.NET Decimal or double, precision could be lost.

The OracleDataAdapter Safe Type Mapping feature prevents data loss when populating Oracle data for any of these types into a .NET DataSet. By setting the SafeMapping property appropriately, these types can be safely represented in the DataSet, as either of the following:

.NET byte[] in Oracle format

.NET String

By default, Safe Type Mapping is disabled.

Frank

Hi Patrick,

Thanks for your info and experience. I agree with you that the performance of ODP object-relational mapping is very important.

Frank

Please read carefull, just must use aliases (as in the sample provided by sgreener)

The following should work:

select a.sdogeometry.sdo_gtype from gst_symbol a;

Patrick