DocumentKeys.cs

using Lucene.Net.Linq.Mapping;

namespace Sample1
{
    /// <remarks>
    /// Note how Article and Comment use a different property for their
    /// key. If they both used Id, Lucene.Net.Linq would have no way
    /// to distinguish them as different types of documents.
    /// </remarks> 
    public class Article
    {
        [Field(Key = true)]
        public long ArticleId { get; set; }
    }

    public class Comment
    {
        [Field(Key = true)]
        public long CommentId { get; set; }
    }
}

namespace Sample2
{
    /// <remarks>
    /// In this example a DocumentKey is added to each class
    /// to add a fixed-value field to each document that will
    /// be used to distinguish entities of different types.
    /// 
    /// In this example both Article and Commend use Id as
    /// the unique identifier for each entity.
    /// </remarks> 
    [DocumentKey(FieldName = "Type", Value = "Article")]
    public class Article
    {
        [Field(Key = true)]
        public long Id { get; set; }
    }

    [DocumentKey(FieldName = "Type", Value = "Comment")]
    public class Comment
    {
        [Field(Key = true)]
        public long Id { get; set; }
    }
}