FileGDB.Core 0.1.1

Reading a File Geodatabase

Limited read-only access to the Esri File Geodatabase (also known as File GDB, FileGDB, or FGDB).

About

Esri File Geodatabases store spatial data as relational tables persisted in a bunch of files in a folder with the extension .gdb.

This package contains a pure .NET assembly for reading from a File Geodatabase. The assembly has no dependencies beyond .NET; it does not use Esri's File Geodatabase API nor any other library.

Usage

To start, you provide the path to the .gdb folder that contains the File Geodatabase files to the FileGDB.Open() method. The resulting FileGDB object provides a catalog (list of all tables in the File Geodatabase) and a method to open any table. Example usage:

var gdb = FileGDB.Core.FileGDB.Open(@"path\to\my.gdb");
var allTables = gdb.Catalog; // list of all tables in File GDB
using var table = gdb.OpenTable("TableName");
var geometryType = table.GeometryType;
int tableVersion = table.Version; // 3 for 9.x, 4 for 10.x geodatabase
string fieldName = table.Fields.First().Name;
var fieldType = table.Fields.First().Type;
for (long oid = 1; oid < table.MaxObjectID; oid++)
{
    object[] values = table.ReadRow(oid);
}

Geometries (usually in the SHAPE column) are returned as GeometryBlob objects. GeometryBlob.Bytes gives access to the geometry as stored in the File GDB. GeometryBlob.ShapeBuffer gives access to the geometry as an Esri Shape Buffer byte array and information about the geometry (type, attributes, number of points, access coordinates, etc). Note that these two byte arrays are different encodings of the geometry: the former is part of the File Geodatabase and stores coordinates as variable length integers, the latter is documented in an Esri white paper that comes with the File Geodatabase API and stores coordinates as double (IEEE 754) values.

The library includes a simple WKT (well-known text) writer for geometries. Usage (refer to embedded XML documentation comments for details):

var buffer = new StringBuilder();
var wkt = new WKTWriter(buffer);
// or:
TextWriter writer = ...;
var wkt = new WKTWriter(writer);
// then:
wkt.BeginFoo(); // start a new shape: Point, Polygon, etc.
wkt.AddVertex(x, y[, z][, m][, id]); // repeatedly
wkt.NewPart(); // begin a new part (for multi-part shapes)
wkt.NewPolygon(); // begin a new outer ring (for MultiPolygon)
wkt.EndShape(); // end current shape
// any number of shapes can be written
wkt.Flush(); // optional (flush the underlying writer)
wkt.Dispose(); // flush and dispose the underlying writer

Limitations

• this is experimental code and comes with no warranty
• only a subset of the File Geodatabase is supported
• Raster fields are not supported
• MultiPatch geometries are not supported
• only full table scans are supported
• indices are not used and not accessible
• no concurrency control (no locking)
• strictly read-only (no updates)

References

• Even Rouault's FGDB specification: https://github.com/rouault/dump_gdbtable/wiki/FGDB-Spec
• Esri's File Geodatabase API on GitHub: https://github.com/Esri/file-geodatabase-api

This project would not have been possible without Even Rouault's detailed FGDB specification.