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As an example, after this exercise it should be possible to show both the input data and the output data of a volume model in one and the same map view.



h2. Create a new map layer provider

Add a new folder to the plugin project named _Layers_. In this folder, create a new class named _VolumeModelLayerProvider.cs_ and add the following code:

{code}
using System.Collections.Generic;
using DelftTools.Shell.Gui;
using DeltaShell.Plugin.DemoApp.Models;
using SharpMap.Api.Layers;
using SharpMap.Layers;

namespace DeltaShell.PluginPlugins.DemoAppVolumeModel.Layers
{
       public class VolumeModelMapLayerProvider : IMapLayerProvider
       {
               /// <summary>
                /// Defines that layers can be provided for volume models
                /// </summary>
                public bool CanCreateLayerFor(object data, object parentData)
        {
                   {
            return data is Models.VolumeModel;
               }

                /// <summary>
                /// Creates a volume model group layer
               /// </summary>
               public ILayer CreateLayer(object data, object parentData)
               {
                        var volumeModel = data as Models.VolumeModel;
                        if (volumeModel != null)
                       {
                               return new GroupLayer(volumeModel.Name);
                        }

                        return null;
               }

               /// <summary>
                /// Returns all children for which a child layer should be created in volume model group layers
                /// </summary>
                public IEnumerable<object> ChildLayerObjects(object data)
        {
                   {
            var volumeModel = data as Models.VolumeModel;
                        if (volumeModel != null)
            {
                           {
                // In the end a child layer should be created for both the catchmentbasin input data and the volume output data
                               yield return volumeModel.Basin;
                                yield return volumeModel.Volume;
                       }
                }
       }
}

{code}

{info}

The map layer provider class derives the _IMapLayerProvider_ interface so that it can be registered in the gui plugin (see the next step).

Furthermore, the comments in the code should explain the different parts of the provider implementation.
{info}
{note}

A description on the backgrounds and usage of (group) layers is not part of this tutorial.

{color:#ff0000}*\[TODO\]*{color} {color:#ff0000}Add links to some wiki pages?{color}
{note}


h2. Register the map layer provider in the gui plugin class

Register the map layer provider in the gui plugin by adding the following code to _VolumeModelGuiPlugin.cs_:

{code}
using DeltaShell.Plugin.DemoApp.Layers;
{code}

and

{code

The map layer provider class is derived from the IMapLayerProvider interface so that it can be registered in the gui plugin (see the next step).

The comments in the code explain the different parts of the provider implementation.

A description on the backgrounds and usage of (group) layers is not part of this tutorial.

using DeltaShell.Plugins.VolumeModel.Layers;

}
        public override IMapLayerProvider MapLayerProvider
        {
            get { return new VolumeModelMapLayerProvider(); }
        }
{code}

The order of the different data layers in a map view can be adjusted using the context menus in the Map window (right click on a data layer | Order | ... ).

Additionally, WMS layers can be included to help identifying the actual geographical location of map data. Follow these steps:

1. Add a new WMS layer to the map using the Map window (click the Add New Wms Layer ... button). In the Open web link ... dialog, select Microsoft Bing Maps - Satellite Hybrid. A new map layer will be added to the view. However, this layer is initially projected using a different coordinate system than the one for the volume output data:
   
   Image Added
   
   
   
2. Select the same coordinate systems for the different map layers in the Map window (right click on the map group layer | Change Map Coordinate System ...). In the corresponding dialog, look for the coordinate system WGS_1984_Web_Mercator and assign it to all layers in the group. The map view should now represent all layers using the same coordinate system. Zoom to the volume group layer (right click on the volume model group layer in the Map window | Zoom to Extend) to see all data at their appropriate location:
   
   Image Added