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    <p>After looking at the sources for NHibernate, I'm fairly sure that there exists no such functionality.</p> <p><em>I wouldn't mind, however, for someone to prove me wrong.</em></p> <p><strong>In my specific setting</strong>, I did solve this problem by writing a method that takes a couple of lambdas (representing the key column, and an optional column to filter by - all properties of a specific domain entity). This method then builds the sql and calls <code>session.CreateSQLQuery(...).UniqueResult();</code> I'm not claiming that this is a general purpose solution.</p> <p>To avoid the use of magic strings, I borrowed a copy of <code>PropertyHelper&lt;T&gt;</code> from <a href="https://stackoverflow.com/questions/491429/how-to-get-the-propertyinfo-of-a-specific-property/491486#491486">this answer</a>.</p> <p>Here's the code:</p> <pre><code>public abstract class RepositoryBase&lt;T&gt; where T : DomainEntityBase { public long GetIndexOf&lt;TUnique, TWhere&gt;(T entity, Expression&lt;Func&lt;T, TUnique&gt;&gt; uniqueSelector, Expression&lt;Func&lt;T, TWhere&gt;&gt; whereSelector, TWhere whereValue) where TWhere : DomainEntityBase { if (entity == null || entity.Id == Guid.Empty) { return -1; } var entityType = typeof(T).Name; var keyField = PropertyHelper&lt;T&gt;.GetProperty(uniqueSelector).Name; var keyValue = uniqueSelector.Compile()(entity); var innerWhere = string.Empty; if (whereSelector != null) { // Builds a column name that adheres to our naming conventions! var filterField = PropertyHelper&lt;T&gt;.GetProperty(whereSelector).Name + "Id"; if (whereValue == null) { innerWhere = string.Format(" where [{0}] is null", filterField); } else { innerWhere = string.Format(" where [{0}] = :filterValue", filterField); } } var innerQuery = string.Format("(select [{0}], row_number() over (order by {0}) as RowNum from [{1}]{2}) X", keyField, entityType, innerWhere); var outerQuery = string.Format("select RowNum from {0} where {1} = :keyValue", innerQuery, keyField); var query = _session .CreateSQLQuery(outerQuery) .SetParameter("keyValue", keyValue); if (whereValue != null) { query = query.SetParameter("filterValue", whereValue.Id); } var sqlRowNumber = query.UniqueResult&lt;long&gt;(); // The row_number() function is one-based. Our index should be zero-based. sqlRowNumber -= 1; return sqlRowNumber; } public long GetIndexOf&lt;TUnique&gt;(T entity, Expression&lt;Func&lt;T, TUnique&gt;&gt; uniqueSelector) { return GetIndexOf(entity, uniqueSelector, null, (DomainEntityBase)null); } public long GetIndexOf&lt;TUnique, TWhere&gt;(T entity, Expression&lt;Func&lt;T, TUnique&gt;&gt; uniqueSelector, Expression&lt;Func&lt;T, TWhere&gt;&gt; whereSelector) where TWhere : DomainEntityBase { return GetIndexOf(entity, uniqueSelector, whereSelector, whereSelector.Compile()(entity)); } } public abstract class DomainEntityBase { public virtual Guid Id { get; protected set; } } </code></pre> <p>And you use it like so:</p> <pre><code>... public class Book : DomainEntityBase { public virtual string Title { get; set; } public virtual Category Category { get; set; } ... } public class Category : DomainEntityBase { ... } public class BookRepository : RepositoryBase&lt;Book&gt; { ... } ... var repository = new BookRepository(); var book = ... a persisted book ... // Get the index of the book, sorted by title. var index = repository.GetIndexOf(book, b =&gt; b.Title); // Get the index of the book, sorted by title and filtered by that book's category. var indexInCategory = repository.GetIndexOf(book, b =&gt; b.Title, b =&gt; b.Category); </code></pre> <p>As I said, this works for me. I'll definitely tweak it as I move forward. YMMV.</p> <p>Now, if the OP has solved this himself, then I would love to see his solution! :-)</p>
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    1. USChristoffer Lette
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    1. COgreat, I might give it a go if my projection plan fails :)
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      1. USYonatan Karni
 

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