Vishful thinking…

Inserting spatial data in SQL Server 2008

Posted in .NET, C#, GIS by viswaug on September 29, 2008

I have been working on inserting data from FeatureClasses into SQL Server 2008 tables. There are a lot of examples online showing how spatial data can be inserted into SQL Server 2008 tables. Here is one from Hannes.

I took from cue from there and proceeded to do what every good programmer should do…parameterize the INSERT query. Here is a simplified version of the scenario I was trying to tackle…

sqlCommand.CommandText = INSERT INTO foo (id, geom) VALUES(1,@g);

sqlCommand.InsertParameter(“@g”, ‘POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))’);

The above INSERT command worked fine. But I also wanted to insert the geometry or geography with the WKID value from the FeatureClass. So I changed the above INSERT statement to use the geometry’s static method and provided the WKID as below

sqlCommand.InsertParameter(“@g”, ‘geometry::STGeomFromText(POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0)), 0)’);

But that didn’t go quite as expected. The INSERT statement was throwing an error saying that it did not recognize ‘geometry::STGeomFromText’ and was expecting ‘POINT, POLYGON, LINESTRING…’ etc.

System.FormatException: 24114: The label geometry::STGeomFrom in the input well-known text (WKT) is not valid. Valid labels are POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, or GEOMETRYCOLLECTION.

This led me to use the Udt SqlParamter type to get around the problem like below. This way I could use the SqlGeometry type in the ‘Microsoft.SqlServer.Types’ namespace and set the SRID directly on its ‘STSRID’ property. The ‘SqlGeometry’ and ‘SqlGeography’ types can be found in the Feature Pack for SQL Server 2008 that can be found here. The SqlGeometry reference can then be used as the value for the SqlParameter.

SqlParameter parameter = new SqlParameter( parameterName, value );

parameter.Direction = ParameterDirection.Input;
parameter.ParameterName = parameterName;
parameter.SourceColumn = sourceColumn;
parameter.SqlDbType = SqlDbType.Udt;
parameter.UdtTypeName = “GEOMETRY”;
parameter.SourceVersion = DataRowVersion.Current;

command.Parameters.Add( parameter );

The ‘UdtTypeName’ should be set to ‘GEOGRAPHY’ for inserting geography fields.

And it worked like a charm.

Update: Heard from Morten saying that using the SqlGeography and SqlGeometry types are almost twice as fast as using WKB (Well Known Binary). Using WKB is by itself faster than using WKT (Well Known Text).

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