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c#nhibernatedynamicpagination
Pabitra Mohan
Pabitra Mohan

Reputation: 11

Nhibernate Criteria make dynamic query and get the row count

I am in big need of help.

I am making dynamic query using Criteria:

ICriteria query = session.CreateCriteria(typeof(Employee));

if (searchOptions.FirstName != null)
{
  query.Add(Expression.Eq("FirstName", searchOptions.FirstName));
}

if (!searchOptions.LastName != null)
{
  query.Add(Expression.Eq("LastName", searchOptions.LastName));
}

if (searchOptions.PhoneNumber != null)
{
  query.CreateCriteria("PhoneNumbers")
    .Add(Expression.Like("Number", searchOptions.PhoneNumber + "%"));
}

After this I need to have both Total Row Count and Pagination.

For pagination:

query.SetFirstResult(0).SetMaxResults(8);

for rowcount:

 query.SetProjection(Projections.RowCountInt64());

How can I execute both in a single query either by using a MultiCriteria or something else.

Please help!

Upvotes: 1

Views: 4105

Answers (1)

Andreas Paulsson
Andreas Paulsson

Reputation: 7803

You can see my answer in nhibernate 2.0 Efficient Data Paging DataList Control and ObjectDataSource .

Code again:

    protected IList<T> GetByCriteria(
        ICriteria criteria, 
        int pageIndex,
        int pageSize, 
        out long totalCount)
    {
        ICriteria recordsCriteria = CriteriaTransformer.Clone(criteria);

        // Paging.
        recordsCriteria.SetFirstResult(pageIndex * pageSize);
        recordsCriteria.SetMaxResults(pageSize);

        // Count criteria.
        ICriteria countCriteria = CriteriaTransformer.TransformToRowCount(criteria);

        // Perform multi criteria to get both results and count in one trip to the database.
        IMultiCriteria multiCriteria = Session.CreateMultiCriteria();
        multiCriteria.Add(recordsCriteria);
        multiCriteria.Add(countCriteria);
        IList multiResult = multiCriteria.List();

        IList untypedRecords = multiResult[0] as IList;
        IList<T> records = new List<T>();
        if (untypedRecords != null)
        {
            foreach (T obj in untypedRecords)
            {
                records.Add(obj);
            }
        }
        else
        {
            records = new List<T>();
        }

        totalCount = Convert.ToInt64(((IList)multiResult[1])[0]);

        return records;
    }

It clones your original criteria twice: one criteria that return the records for the page and one criteria for total record count. It also uses IMultiCriteria to perform both database calls in one roundtrip.

Upvotes: 5

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