public void SetShapeType( 
   GeometryType shapeType
)

public async Task MultiGeometryQueryDescription()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
    {
        DatabaseConnectionProperties databaseConnectionProperties = new DatabaseConnectionProperties(EnterpriseDatabaseType.SQLServer)
        {
            AuthenticationMode = AuthenticationMode.DBMS,
            Instance = "instance",
            Database = "database",
            User = "user",
            Password = "password"
        };

        using (Database database = new Database(databaseConnectionProperties))
        {
            QueryDescription pointQueryDescription = database.GetQueryDescription("select Description, SHAPE, UniqueID from MULTIGEOMETRYTEST", "MultiGeometryPoint");
            pointQueryDescription.SetShapeType(GeometryType.Point);
            using (Table pointTable = database.OpenTable(pointQueryDescription))
            {
                //use pointTable
            }

            QueryDescription polygonQueryDescription = database.GetQueryDescription("select Description, SHAPE, UniqueID from MULTIGEOMETRYTEST", "MultiGeometryPolygon");
            polygonQueryDescription.SetShapeType(GeometryType.Polygon);
            using (Table polygonTable = database.OpenTable(polygonQueryDescription))
            {
                //use polygonTable
            }
        }
    });
}