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copied!<p>I believe the problem is that Linq/NHibernate is trying to map IEntity.Id to a table column instead of TEntity.Id. I had this problem with a LinqToSql repository implementation. The way around it was to use an expression like this:</p> <pre><code>private static Expression<Func<TEntity, bool>> GetFindExpression(string propertyName, object value) { ParameterExpression parameterExpression = Expression.Parameter(typeof (TEntity), "id"); MemberExpression propertyExpression = Expression.Property(parameterExpression, propertyName); Expression bodyExpression = Expression.Equal(propertyExpression, Expression.Constant(value)); return Expression.Lambda<Func<TEntity, bool>>(bodyExpression, parameterExpression); } </code></pre> <p>So this would change Get(id) to:</p> <pre><code>public TEntity Get(int id) { var entities = Query.Where(GetFindExpression("Id", id)); return entities.FirstOrDefault(); } </code></pre> <p><strong>Update:</strong></p> <p>If you don't want to deal with expressions (they can be tricky!), you could use the Dynamic LINQ library as described by Scott Guthrie here: <a href="http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx" rel="nofollow noreferrer">http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx</a></p> <p>That would change Get(id) to:</p> <pre><code>public TEntity Get(int id) { var entities = Query.Where("Id = @0", id); return entities.FirstOrDefault(); } </code></pre>

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