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WP7Contrib: Criterion Factory - Location by search by latitude & longitude

To kick off the series about the Criterion Factory in the Bing Maps service I thought I'd start with the easiest functionality - searching for a location using latitude & longitude.

Firstly here is the code - I have to emphasize how easy this is to use. It has taken only 5 lines of code to get the location information and the only required is a set of WP7Contrib assembly references.

private void locationByPointClick(object sender, RoutedEventArgs e)
{
    var geoCoordinate = new GeoCoordinate(Convert.ToDouble(this.lat.Text), Convert.ToDouble(this.@long.Text));
   
var criterion = CriterionFactory.CreateLocationSearchForPoint(geoCoordinate);

    this.bingMapsService.SearchForLocationUsingPoint(criterion)
        .ObserveOnDispatcher()
        .Subscribe(result =>
        {
            this.address.Text = result.Locations[0].Address.Locality;
            this.address.Text += Environment.NewLine;
            this.address.Text += result.Locations[0].Address.PostalCode;
            this.address.Text += Environment.NewLine;
            this.address.Text += result.Locations[0].Address.AdminDistrict;
            this.address.Text += Environment.NewLine;
            this.address.Text += result.Locations[0].Address.CountryRegion;
        });
}

Secondly, here is a screenshot of the end-to-end example, creating the criterion and executing the SearchForLocationUsingPoint() method and showing the results on the emulator, you can also see the logging in the visual studio output window.


I've highlight the line we are interested, the creation of the criterion for use with the service. As I said this was probably the easiest one to document, there is only one overload for this method, shown below. The 'includeEntities' parameter allows you to define what information will be returned for the query, as the documentation says this is optional, hence the overloaded method. More info about the types supported can be found on MSDN.

As you can see we do some primitive validation of the parameters used to create the criterion - we never to do much more than check for nulls if the parameter is required or an explicit optional parameter. These simple rules have been extracted from the MSDN documentation. Later in this series we will see validation rules for more complicated parameters.

#region LocationSearchForPoint

public static ILocationSearchPointCriterion CreateLocationSearchForPoint(GeoCoordinate point)
{
    return CreateLocationSearchForPoint(point, new List<LocationEntity>());
}

public static ILocationSearchPointCriterion CreateLocationSearchForPoint(GeoCoordinate point, IList<LocationEntity> includeEntities)
{
    if (point == null)
        throw new ArgumentNullException("point", "Point is null.");

    if (point == GeoCoordinate.Unknown)
        throw new ArgumentException("Point is unknown.", "point");

    if (includeEntities == null)
        throw new ArgumentNullException("includeEntities", "Include Entities can not be null.");

    var criterion = new LocationSearchCriterion { Point = point };
    criterion.IncludedEntities.AddRange(includeEntities);

    return criterion;
}

#endregion

You'll also notice from the above code snippet the return value for the overloaded methods - ILocationSearchPointCriterion. The Bing Maps service only accepts a criterion interface as a parameter, thes reason for this is to reduced the number of parameters. The Bing Maps service interface for searching for locations is shown below:

/// <summary>
/// Defines the interface for searching for location information using the Bing Maps API.
/// </summary>
public interface IBingLocationService
{
    IObservable<LocationSearchResult> SearchForLocationUsingAddress(ILocationSearchAddressCriterion criterion);
    IObservable<LocationSearchResult> SearchForLocationUsingPoint(ILocationSearchPointCriterion criterion);
    IObservable<LocationSearchResult> FindLocationUsingQuery(ILocationSearchQueryCriterion criterion);
}

The ILocationSearchPointCriterion is a simple read-only interface preventing changing of a criterion once created (if you only have a reference to the interface), see below. This was explicitly done because the criterion has to be immutable because it is used as part of the internal caching key inside the Bing Maps service. Similarly we want to be able to clone the criterion hence the implementation of the WP7Contrib interface ICloneable.

public interface ILocationSearchPointCriterion : ICloneable<ILocationSearchPointCriterion>
{
    GeoCoordinate Point { get; }
    ObservableCollection<LocationEntity> IncludedEntities { get; }

    bool HasPoint { get; }
    bool HasIncludedEntities { get; }
}

This interface is implemented by the LocationSearchCriterion class, this is a bindable model class that implements public getters & setters for the Point & IncludedEntities parameters. In theory you could bind these properties directly to the UI and then pass the class to the service without needing an intermediate View Model variables\properties. This class also implements the equality operators and IEquatable interface, this is required again for the internal caching in the Bing Maps service.

I've shown the LocationSearchCriterion class below, in future posts I'm nothing to show criterion class unless there is a special case as they are rather long in length.

public class LocationSearchCriterion : BaseModel, ICriterion<LocationSearchCriterion>,
                                                    IEquatable<LocationSearchCriterion>,
                                                    ICloneable<LocationSearchCriterion>,
                                                    ILocationSearchQueryCriterion,
                                                    ILocationSearchAddressCriterion,
                                                    ILocationSearchPointCriterion
{
    private Address address;
    private GeoCoordinate point;
    private string query;
    private ObservableCollection<LocationEntity> includeEntities;

    public LocationSearchCriterion()
    {
        this.Reset();
    }

    public Address Address
    {
        get
        {
            return address;
        }
        set
        {
            this.SetPropertyAndNotify(ref this.address, value, () => this.Address);
        }
    }

    public bool HasAddress
    {
        get {  return this.address != null && this.address != Address.Empty; }
    }

    public GeoCoordinate Point
    {
        get
        {
            return this.point;
        }
        set
        {
            this.SetPropertyAndNotify(ref this.point, value, () => this.Point);
        }
    }

    public bool HasPoint
    {
        get { return this.point != null && this.point != GeoCoordinate.Unknown; }
    }

    public string Query
    {
        get
        {
            return this.query;
        }
        set
        {
            this.SetPropertyAndNotify(ref this.query, value, () => this.Query);
        }
    }

    public bool HasQuery
    {
        get { return string.IsNullOrEmpty(this.query); }
    }

    public ObservableCollection<LocationEntity> IncludedEntities
    {
        get
        {
            return this.includeEntities;
        }
        set
        {
            this.SetPropertyAndNotify(ref this.includeEntities, value, () => this.IncludedEntities);
        }
    }

    public bool HasIncludedEntities
    {
        get { return this.includeEntities != null && this.includeEntities.Count != 0; }
    }

    public LocationSearchCriterion Reset()
    {
        this.address = new Address();
        this.point = new GeoCoordinate();
        this.query = null;

        this.includeEntities = new ObservableCollection<LocationEntity>();

        return this;
    }

    public static bool operator ==(LocationSearchCriterion lsc1, LocationSearchCriterion lsc2)
    {
        return Equals(lsc1, lsc2);
    }

    public static bool operator !=(LocationSearchCriterion lsc1, LocationSearchCriterion lsc2)
    {
        return !Equals(lsc1, lsc2);
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj))
        {
            return false;
        }

        return obj is LocationSearchCriterion && this.Equals((LocationSearchCriterion)obj);
    }

    public override int GetHashCode()
    {
        return this.CombineHashCodes(this.Address, this.Point);
    }

    public bool Equals(LocationSearchCriterion criterion)
    {
        if (ReferenceEquals(null, criterion))
        {
            return false;
        }

        if (this.Address != criterion.Address)
        {
            return false;
        }

        if (this.Point != criterion.Point)
        {
            return false;
        }

        if (this.Query != criterion.Query)
        {
            return false;
        }

        return true;
    }

    ILocationSearchAddressCriterion ICloneable<ILocationSearchAddressCriterion>.ShallowClone()
    {
        return this.ShallowClone();
    }

    ILocationSearchPointCriterion ICloneable<ILocationSearchPointCriterion>.ShallowClone()
    {
        return this.ShallowClone();
    }

    ILocationSearchQueryCriterion ICloneable<ILocationSearchQueryCriterion>.ShallowClone()
    {
        return this.ShallowClone();
    }

    public LocationSearchCriterion ShallowClone()
    {
        var criterion = new LocationSearchCriterion
                            {
                                Address = this.Address,
                                Point = this.Point,
                                Query = this.Query
                            };
        return criterion;
    }

    ILocationSearchAddressCriterion ICloneable<ILocationSearchAddressCriterion>.DeepClone()
    {
        return this.DeepClone();
    }

    ILocationSearchPointCriterion ICloneable<ILocationSearchPointCriterion>.DeepClone()
    {
        return this.DeepClone();
    }

    ILocationSearchQueryCriterion ICloneable<ILocationSearchQueryCriterion>.DeepClone()
    {
        return this.DeepClone();
    }

    public LocationSearchCriterion DeepClone()
    {
        var criterion = new LocationSearchCriterion
                            {
                                Query = this.Query
                            };

        if (this.HasAddress)
            criterion.Address = this.Address.DeepClone();

        if (this.HasPoint)
            criterion.Point = new GeoCoordinate(this.Point.Latitude, this.Point.Longitude);

        return criterion;
    }
}

That pretty covers it!

If you want to use the demo you can, it can found in the WP7Contrib Spikes in the 'BingMaps_CriterionFactory' directory. You'll have to have a Bing AppID to use the service & demo, you can register here.




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