ActiveRecord/Castle.ActiveRecord/Framework/Queries/ScalarProjectionQuery.cs

   1 // Copyright 2004-2008 Castle Project - http://www.castleproject.org/
   2 //
   3 // Licensed under the Apache License, Version 2.0 (the "License");
   4 // you may not use this file except in compliance with the License.
   5 // You may obtain a copy of the License at
   6 //
   7 //     http://www.apache.org/licenses/LICENSE-2.0
   8 //
   9 // Unless required by applicable law or agreed to in writing, software
  10 // distributed under the License is distributed on an "AS IS" BASIS,
  11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 // See the License for the specific language governing permissions and
  13 // limitations under the License.
  14
  15 namespace Castle.ActiveRecord.Queries
  16 {
  17         using System;
  18         using System.Collections;
  19         using NHibernate;
  20         using NHibernate.Expressions;
  21
  22         /// <summary>
  23         /// Perform a scalar projection ( aggeregate ) type of query:
  24         /// avg, max, count(*), etc.
  25         /// </summary>
  26         /// <typeparam name="ARType">The type of the entity we are querying</typeparam>
  27         /// <typeparam name="TResult">The type of the scalar from this query</typeparam>
  28         /// <example>
  29         /// <code>
  30         /// ScalarProjectionQuery&lt;Blog, int&gt; proj = new ScalarProjectionQuery&lt;Blog, int&gt;(Projections.RowCount());
  31         /// int rowCount = proj.Execute();
  32         /// </code>
  33         /// </example>
  34         public class ScalarProjectionQuery<ARType, TResult> : IActiveRecordQuery<TResult>
  35         {
  36                 private readonly IProjection projection;
  37                 private readonly ICriterion[] criterions;
  38                 private readonly DetachedCriteria detachedCriteria;
  39
  40                 /// <summary>
  41                 /// Initializes a new instance of the <see cref="ScalarProjectionQuery{ARType,TResult}"/> class.
  42                 /// </summary>
  43                 /// <param name="projection">The projection.</param>
  44                 /// <param name="criterions">The criterions.</param>
  45                 public ScalarProjectionQuery(IProjection projection, params ICriterion[] criterions)
  46                 {
  47                         this.projection = projection;
  48                         this.criterions = criterions;
  49                 }
  50
  51                 /// <summary>
  52                 /// Initializes a new instance of the <see cref="ScalarProjectionQuery{ARType,TResult}"/> class.
  53                 /// </summary>
  54                 /// <param name="projection">The projection.</param>
  55                 /// <param name="criteria">The detached criteria.</param>
  56                 public ScalarProjectionQuery(IProjection projection, DetachedCriteria criteria)
  57                 {
  58                         this.projection = projection;
  59                         detachedCriteria = criteria;
  60                 }
  61
  62                 /// <summary>
  63                 /// Gets the target type of this query
  64                 /// </summary>
  65                 /// <value></value>
  66                 public Type RootType
  67                 {
  68                         get { return typeof(ARType); }
  69                 }
  70
  71                 /// <summary>
  72                 /// Executes the specified query and return the results
  73                 /// </summary>
  74                 /// <param name="session">The session to execute the query in.</param>
  75                 /// <returns>the result of the query</returns>
  76                 object IActiveRecordQuery.Execute(ISession session)
  77                 {
  78                         return Execute(session);
  79                 }
  80
  81                 /// <summary>
  82                 /// Enumerates over the result of the query.
  83                 /// Always returns a single result
  84                 /// </summary>
  85                 public IEnumerable Enumerate(ISession session)
  86                 {
  87                         yield return Execute(session);
  88                 }
  89
  90                 /// <summary>
  91                 /// Executes the specified query and return the results
  92                 /// </summary>
  93                 /// <param name="session">The session to execute the query in.</param>
  94                 /// <returns>the result of the query</returns>
  95                 public TResult Execute(ISession session)
  96                 {
  97                         if (detachedCriteria != null)
  98                         {
  99                                 return detachedCriteria.GetExecutableCriteria(session)
 100                                         .SetProjection(projection)
 101                                         .UniqueResult<TResult>();
 102                         }
 103                         else
 104                         {
 105                                 ICriteria criteria = session.CreateCriteria(RootType);
 106
 107                 CriteriaHelper.AddCriterionToCriteria(criteria, criterions);
 108
 109                 criteria.SetProjection(projection);
 110                                 return criteria.UniqueResult<TResult>();
 111                         }
 112                 }
 113
 114                 /// <summary>
 115                 /// Executes the specified query and return the results
 116                 /// </summary>
 117                 /// <returns>the result of the query</returns>
 118                 public TResult Execute()
 119                 {
 120                         return (TResult) ActiveRecordMediator.ExecuteQuery(this);
 121                 }
 122         }
 123 }