esri json.cs

ReadLayerQuery.cs

/// <summary>
/// Parses the results of a query operation against the layer
/// in to <see cref="Feature"/>s.
/// </summary>
/// <param name="dataSourceFields">List of valid fields</param>
/// <param name="geometryType"></param>
/// <param name="json"></param>
/// <returns></returns>
/// <remarks>Because the collection of fields can vary between each layer and even
/// between query results for each layer this actually has a two phased approach to loading
/// the data. First it loads the geometries using <see cref="Newtonsoft.Json.Linq"/> methods
/// ; this is possible because the structure of geometries is constant. Then it uses
/// a <see cref="JsonTextReader"/> to rip through the rest of the JSON content parsing
/// out the fields and their values. A bit awkward but really the only way to go given
/// the mutable list of fields, field names, and field values.</remarks>
private static IList<Feature> ReadLayerQueryResults(IEnumerable<Field> dataSourceFields, EsriGeometryType geometryType, string json)
{
	IList<Feature> features = null;
	if (string.IsNullOrEmpty(json)) return features;

	// First the geometries.
	IList<IGeometry> geometries = null;

	// TODO - I *think* this handles rasters and tables OK. but need to check again.
	if (geometryType != EsriGeometryType.NoGeometry)
	{
		geometries = RestClient.BuildGeometryFromJson(geometryType, json);
		if (geometries == null || geometries.Count == 0) return features;
	}

	var geometryIndex = 0;

	// Then the attributes
	JsonReader reader = new JsonTextReader(new StringReader(json));

	while (reader.Read())
	{
		while (Convert.ToString(reader.Value) != "features")
		{
			reader.Read();
		}

		// Found feature collections
		features = new List<Feature>();

		while (reader.Read())
		{
			var feature = new Feature();

			if (Convert.ToString(reader.Value) == "attributes")
			{
				// Found the attributes for a feature - this always comes
				// before the geometry if the geometry is even present
				IAttributesTable table = new AttributesTable();
				reader.Read();

				do
				{
					// As long as we're still in the attribute list...
					if (reader.TokenType == JsonToken.PropertyName)
					{
						var fieldName = Convert.ToString(reader.Value);
						reader.Read();
						Field field = dataSourceFields.SingleOrDefault(f => f.Name.ToUpperInvariant() == fieldName.ToUpperInvariant());
						object value = reader.Value == null
							? null
							: Convert.ChangeType(reader.Value, field.DataType);
						if (!table.Exists(fieldName)) table.AddAttribute(fieldName, null);
						table[fieldName] = value;
					}

					reader.Read();

				} while (reader.TokenType != JsonToken.EndObject
						 && Convert.ToString(reader.Value) != "attributes");

				feature.Attributes = table;

				if (geometries != null)
				{
					feature.Geometry = geometries[geometryIndex];
					geometryIndex++;
				}
			}

			// Was checking if feature null as well but a standalone table
			// in an MXD being served up does not have a spatial component
			// to turn in to geometries.
			if (feature.Attributes == null) continue;

			if (feature.Geometry != null & geometryType != EsriGeometryType.NoGeometry)
			{
				features.Add(feature);
			}
			else if (feature.Geometry == null & geometryType == EsriGeometryType.NoGeometry)
			{
				features.Add(feature);
			}
		}
	}

	return features;
}