DatasetGraphCollection.cs

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using System;
using System.Collections.Generic;
using System.Linq;

namespace VDS.RDF.Query.Datasets
{
    /// <summary>
    /// A Graph Collection which wraps an <see cref="ISparqlDataset">ISparqlDataset</see> implementation so it can be used as if it was a Graph Collection.
    /// </summary>
    public class DatasetGraphCollection
        : BaseGraphCollection
    {
        private ISparqlDataset _dataset;

        /// <summary>
        /// Creates a new Dataset Graph collection.
        /// </summary>
        /// <param name="dataset">SPARQL Dataset.</param>
        public DatasetGraphCollection(ISparqlDataset dataset)
        {
            _dataset = dataset;
        }

        /// <summary>
        /// Gets whether the Collection contains a Graph with the given URI.
        /// </summary>
        /// <param name="graphUri">Graph URI.</param>
        /// <returns></returns>
        public override bool Contains(Uri graphUri)
        {
            return _dataset.HasGraph(graphUri);
        }

        /// <summary>
        /// Adds a Graph to the Collection.
        /// </summary>
        /// <param name="g">Graph to add.</param>
        /// <param name="mergeIfExists">Whether to merge the given Graph with any existing Graph with the same URI.</param>
        /// <exception cref="RdfException">Thrown if a Graph with the given URI already exists and the <paramref name="mergeIfExists">mergeIfExists</paramref> is set to false.</exception>
        protected internal override bool Add(IGraph g, bool mergeIfExists)
        {
            if (Contains(g.BaseUri))
            {
                if (mergeIfExists)
                {
                    IGraph temp = _dataset.GetModifiableGraph(g.BaseUri);
                    temp.Merge(g);
                    temp.Dispose();
                    _dataset.Flush();
                    return true;
                }
                else
                {
                    throw new RdfException("Cannot add this Graph as a Graph with the URI '" + g.BaseUri.ToSafeString() + "' already exists in the Collection and mergeIfExists was set to false");
                }
            }
            else
            {
                // Safe to add a new Graph
                if (_dataset.AddGraph(g))
                {
                    _dataset.Flush();
                    RaiseGraphAdded(g);
                    return true;
                }
                return false;
            }
        }

        /// <summary>
        /// Removes a Graph from the Collection.
        /// </summary>
        /// <param name="graphUri">URI of the Graph to removed.</param>
        protected internal override bool Remove(Uri graphUri)
        {
            if (Contains(graphUri))
            {
                IGraph temp = _dataset[graphUri];
                bool removed = _dataset.RemoveGraph(graphUri);
                _dataset.Flush();
                RaiseGraphRemoved(temp);
                temp.Dispose();
                return removed;
            }
            return false;
        }

        /// <summary>
        /// Gets the number of Graphs in the Collection.
        /// </summary>
        public override int Count
        {
            get 
            {
                return _dataset.GraphUris.Count(); 
            }
        }

        /// <summary>
        /// Gets the URIs of Graphs in the Collection.
        /// </summary>
        public override IEnumerable<Uri> GraphUris
        {
            get 
            {
                return _dataset.GraphUris;
            }
        }

        /// <summary>
        /// Gets the Graph with the given URI.
        /// </summary>
        /// <param name="graphUri">Graph URI.</param>
        /// <returns></returns>
        public override IGraph this[Uri graphUri]
        {
            get 
            {
                if (_dataset.HasGraph(graphUri))
                {
                    return _dataset[graphUri];
                }
                else
                {
                    throw new RdfException("The Graph with the given URI does not exist in this Graph Collection");
                }
            }
        }

        /// <summary>
        /// Disposes of the Graph Collection.
        /// </summary>
        public override void Dispose()
        {
            _dataset.Flush();
        }

        /// <summary>
        /// Gets the enumeration of Graphs in this Collection.
        /// </summary>
        /// <returns></returns>
        public override IEnumerator<IGraph> GetEnumerator()
        {
            return _dataset.Graphs.GetEnumerator();
        }
    }
}