WMS Layers Not Displaying in Runtime Without Name

Question

How do I display the "root" layer in a WMS service using Runtime for .NET sdk? This layer does not have a name property in the xml capabilities so I'm not sure how to specify it for the Layers property on the WmsLayer. I can't seem to get any of the layers for this service to display. I have tested with other services and they do seem to work when I specify the Layer's Name property, when every Layer in the WMS has a Name. https://idpgis.ncep.noaa.gov/arcgis/services/NWS_Observations/NOHRSC_Snow_Analysis/MapServer/WmsServer?service=wms&request=GetCapabilities This is an example xml: <![CDATA[ Layers ]]>CRS:84EPSG:4326EPSG:0-130.516667-62.25273124.10000058.240301<![CDATA[ Snow Water Equivalent ]]>CRS:84EPSG:4326EPSG:0-130.516666-62.25273124.10000058.2403011<![CDATA[ Inches ]]>CRS:84EPSG:4326EPSG:0

MatveiStefarov · Answer

Only named layers hold data in a WMS service. Unnamed layers are only used for logical grouping and metadata. The WMS specification provides more details (section 7.2.4): Conceptually, each Layer is a distinct entity. However, as a means of classifying and organizing layers, and as a means of reducing the size of the service metadata, a single parent Layer may enclose any number of additional layers, which may be hierarchically nested as desired. <...> If, and only if, a layer has a , then it is a map layer that can be requested by using that Name in the LAYERS parameter of a GetMap request. A Layer that contains a element is referred to as a “named layer” in this International Standard. If the layer has a Title but no Name, then that layer is only a category title for all the layers nested within. A server that advertises a Layer containing a Name element shall be able to accept that Name as the value of LAYERS argument in a GetMap request and return the corresponding map. A client shall not attempt to request a layer that has a Title but no Name. Runtime's WMSLayer takes a flattened list of named layers to display, ordered bottom-to-top. For this particular service, displaying the "root" layer just means creating a WMSLayer from names "1", "2", "3", "5", "6", and "7". For a more general solution, you can examine WMSLayerInfo and gather all of its named sublayers recursively, like so: ///

/// Gathers a flat list of named layers for a given WMSLayerInfo, recursively. ///

/// Parent node to begin the search at. /// A list to be populated with named WmsLayerInfo objects. void GetNamedLayers(WmsLayerInfo startingNode, List<WmsLayerInfo> collector) { if (!String.IsNullOrEmpty(startingNode.Name)) { // Add this named layer to the list collector.Add(startingNode); } else { // For category layers: look for named children foreach (var sublayer in startingNode.LayerInfos) { GetNamedLayers(sublayer, collector); } } }‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ Example usage: // Load service metadata var serviceUrl = new Uri("https://idpgis.ncep.noaa.gov/arcgis/services/NWS_Observations/NOHRSC_Snow_Analysis/MapServer/WmsServer?service=wms&request=GetCapabilities"); var service = new WmsService(serviceUrl); await service.LoadAsync(); // Gather a list of all named WMSLayerInfos on this service var list = new List<WmsLayerInfo>(); foreach (var layerInfo in service.ServiceInfo.LayerInfos) { GetNamedLayers(layerInfo, list); } // Create a layer containing ALL named sublayers from this service, in order of declaration. // Note: First layer in the list will be drawn first (at the bottom), // and last layer will be drawn last (on top of everything else). var layer = new WmsLayer(list); await layer.LoadAsync();‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍