PostGIS - Práce s GIS vrstvami v PostgreSQL databázích pomocí C#

PostgreSQL (rozšíření PostGIS) jsou jedny z nejrozšířenějších databází mezi GIS softwarem. Aspose.GIS vám umožňuje pracovat s PostgreSQL databázemi.

Procházení vrstev v databázi PostGis

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
// First, we create the connection to the PostgreSQL with Npgsql library (https://www.nuget.org/packages/Npgsql/)
// Then, we pass this connection to Dataset.Open method in order to access tables in the PostgreSQL.
using (var connection = new NpgsqlConnection(postgreSqlConnectionString))
{
    connection.Open();
    using (var ds = Dataset.Open(connection, Drivers.PostGis))
    {
        // Only spatial tables are exported as layers, so the following code will list all tables
        // that have geometry column.
        for (int i = 0; i < ds.LayersCount; ++i)
        {
            Console.WriteLine(ds.GetLayerName(i));
        }
    }
}

Přidání nové vrstvy do databáze PostGis

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
// First, we create the connection to the PostgreSQL with Npgsql library (https://www.nuget.org/packages/Npgsql/)
using (var connection = new NpgsqlConnection(postgreSqlConnectionString))
{
    connection.Open();
    // Then, we pass this connection to Dataset.Open method in order to access tables in the PostgreSQL.
    using (var ds = Dataset.Open(connection, Drivers.PostGis))
    {
        // create table with the name "features_table" and fill it with data.
        using (var layer = ds.CreateLayer("features_table"))
        {
            layer.Attributes.Add(new FeatureAttribute("name", AttributeDataType.String) { Width = 50 });

            var feature = layer.ConstructFeature();
            feature.SetValue("name", "Name1");
            feature.Geometry = Geometry.FromText("POINT (10 20 30)");
            layer.Add(feature);

            feature = layer.ConstructFeature();
            feature.SetValue("name", "Name2");
            feature.Geometry = Geometry.FromText("POINT (-10 -20 -30)");
            layer.Add(feature);
        }
    }
}

Export vrstvy z databáze PostGis do souborového formátu

// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
var outputPath = Path.Combine(RunExamples.GetDataDir(), "postgres_out.shp");

// First, we create the connection to the PostgreSQL with Npgsql library (https://www.nuget.org/packages/Npgsql/)
// Then, we pass this connection to Dataset.Open method in order to access tables in the PostgreSQL.
using (var connection = new NpgsqlConnection(postgreSqlConnectionString))
{
    connection.Open();
    using (var ds = Dataset.Open(connection, Drivers.PostGis))
    {
        // open table with the name "features_table" in Postgres database and save it to the shapefile.
        using (var table = ds.OpenLayer("features_table"))
        {
            table.SaveTo(outputPath, Drivers.Shapefile);
        }
    }
}