不确定这是否可行，但无论如何我都会解释。
我有一个自定义投影，可以在一个查询中进行简单的算术运算。
namespace Custom.Projections
{
using System.Collections.Generic;
using System.Text;
using global::NHibernate;
using global::NHibernate.Criterion;
using global::NHibernate.SqlCommand;
using global::NHibernate.Type;
/// <summary>
/// Represents a CalculatedProjection
/// </summary>
public class CalculatedProjection : SimpleProjection
{
private readonly CalculationType calculationType;
private readonly IProjection firstProjection;
private readonly IProjection secondProjection;
private readonly string firstPropertyName;
private readonly string secondPropertyName;
/// <summary>
/// Initializes a new instance of the CalculatedProjection class
/// </summary>
/// <param name="type">The type of calculation</param>
/// <param name="firstPropertyName">The name of the first property</param>
/// <param name="secondPropertyName">The name of the second property</param>
protected internal CalculatedProjection(CalculationType type, string firstPropertyName, string secondPropertyName)
{
this.calculationType = type;
this.firstPropertyName = firstPropertyName;
this.secondPropertyName = secondPropertyName;
System.Diagnostics.Debugger.Launch();
}
/// <summary>
/// Initializes a new instance of the CalculatedProjection class
/// </summary>
/// <param name="type">The type of calculation</param>
/// <param name="firstProjection">The first projection</param>
/// <param name="secondProjection">The second projection</param>
protected internal CalculatedProjection(CalculationType type, IProjection firstProjection, IProjection secondProjection)
{
this.calculationType = type;
this.firstProjection = firstProjection;
this.secondProjection = secondProjection;
}
/// <summary>
/// The type of calculation
/// </summary>
public enum CalculationType
{
/// <summary>
/// Addition +
/// </summary>
Addition,
/// <summary>
/// Subtraction -
/// </summary>
Subtraction,
/// <summary>
/// Division /
/// </summary>
Division,
/// <summary>
/// Division *
/// </summary>
Multiplication,
}
/// <summary>
/// Gets a value indicating whether the projection is grouped
/// </summary>
public override bool IsGrouped
{
get { return false; }
}
/// <summary>
/// Gets a value indicating whether IsAggregate.
/// </summary>
public override bool IsAggregate
{
get { return false; }
}
/// <summary>
/// Converts the calculation into a string
/// </summary>
/// <returns>The string representation of the calculation</returns>
public override string ToString()
{
var firstValue = this.firstProjection != null ? this.firstProjection.ToString() : this.firstPropertyName;
var secondValue = this.secondProjection != null ? this.secondProjection.ToString() : this.secondPropertyName;
return "(" + firstValue + TypeToString(this.calculationType) + secondValue + ")";
}
/// <summary>
/// Gets the types involved in the query
/// </summary>
/// <param name="criteria">The current criteria</param>
/// <param name="criteriaQuery">The criteria query</param>
/// <returns>An array of IType</returns>
public override IType[] GetTypes(ICriteria criteria, ICriteriaQuery criteriaQuery)
{
var types = new List<IType>();
if (this.firstProjection != null)
{
types.AddRange(this.firstProjection.GetTypes(criteria, criteriaQuery));
}
else
{
types.Add(criteriaQuery.GetType(criteria, this.firstPropertyName));
}
if (this.secondProjection != null)
{
types.AddRange(this.secondProjection.GetTypes(criteria, criteriaQuery));
}
else
{
types.Add(criteriaQuery.GetType(criteria, this.secondPropertyName));
}
return types.ToArray();
}
/// <summary>
/// Converts the objects to an sql string representation
/// </summary>
/// <param name="criteria">The criteria being used in the query</param>
/// <param name="loc">The location in the query</param>
/// <param name="criteriaQuery">The criteria query</param>
/// <param name="enabledFilters">List of enabled filters</param>
/// <returns>The calculation as an sql string</returns>
public override SqlString ToSqlString(ICriteria criteria, int loc, ICriteriaQuery criteriaQuery, IDictionary<string, IFilter> enabledFilters)
{
string first, second;
if ((this.firstProjection != null) && (this.secondProjection != null))
{
first = global::NHibernate.Util.StringHelper.RemoveAsAliasesFromSql(this.firstProjection.ToSqlString(criteria, loc, criteriaQuery, enabledFilters)).ToString();
second = global::NHibernate.Util.StringHelper.RemoveAsAliasesFromSql(this.secondProjection.ToSqlString(criteria, loc, criteriaQuery, enabledFilters)).ToString();
}
else
{
first = criteriaQuery.GetColumn(criteria, this.firstPropertyName);
second = criteriaQuery.GetColumn(criteria, this.secondPropertyName);
}
return new SqlString(new object[] { "(", first, TypeToString(this.calculationType), second, ") as y", loc.ToString(), "_" });
}
/// <summary>
/// Converts the objects to an sql string representation
/// </summary>
/// <param name="criteria">The criteria being used in the query</param>
/// <param name="criteriaQuery">The criteria query</param>
/// <param name="enabledFilters">List of enabled filters</param>
/// <returns>The calculation as an sql string</returns>
public override SqlString ToGroupSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery, IDictionary<string, IFilter> enabledFilters)
{
var sb = new StringBuilder();
return new SqlString(new object[] { sb.ToString() });
}
/// <summary>
/// Returns the string symbol of calculation type
/// </summary>
/// <param name="type">The type to use</param>
/// <returns>The string representation</returns>
private static string TypeToString(CalculationType type)
{
switch (type)
{
case CalculationType.Addition: return "+";
case CalculationType.Subtraction: return "-";
case CalculationType.Multiplication: return "*";
case CalculationType.Division: return "/";
default: return "+";
}
}
}
}
我现在尝试使用QueryOver语法在另一个中使用此投影，如下所示：
public override IList<DaySummaryDetail> Execute()
{
// ReSharper disable PossibleNullReferenceException
var calculated = Custom.Projections.Calculated(CalculatedProjection.CalculationType.Subtraction, "Duration.EndTime", "Duration.StartTime");
DaySummaryDetail detail = null;
return Session.QueryOver<WorkingDay>()
.SelectList(list => list
.Select(Projections.Group<WorkingDay>(x => x.Date).WithAlias(() => detail.Date))
.Select(Projections.Sum(calculated)).WithAlias(() => detail.TotalMinutes))
.Where(x => x.Person.Id == 1)
.TransformUsing(Transformers.AliasToBean<DaySummaryDetail>())
.List<DaySummaryDetail>();
// ReSharper restore PossibleNullReferenceException
}
生成的查询是正确的：
SELECT
this_.DATE_TIME as y0_,
sum((this_.END_MINS-this_.START_MINS)) as y1_
FROM
WORKINGDAY this_
WHERE
this_.PERSON_ID = @p0
GROUP BY
this_.DATE_TIME;
@p0 = 1 [Type: Int64 (0)]
我遇到的问题是我得到以下异常：
NHibernate.Exceptions.GenericADOException：无法执行查询 [选择this_.DATE_TIME作为y0_，求和（（this_.END_MINS-this_.START_MINS））为y1_ FROM WORKINGDAY this_ WHERE this_.PERSON_ID = @ p0 GROUP BY this_.DATE_TIME] 名称：cp0 - 值：8977 [SQL：选择this_.DATE_TIME为y0_，sum（（this_.END_MINS-this_.START_MINS））为y1_ FROM WORKINGDAY this_ WHERE this_.PERSON_ID = @ p0 GROUP BY this_.DATE_TIME] ----＆GT; System.IndexOutOfRangeException：y2 _
堆栈跟踪：
at System.Data.SqlClient.SqlDataReader.GetOrdinal(String name)
at NHibernate.Type.NullableType.NullSafeGet(IDataReader rs, String name)
at NHibernate.Loader.Criteria.CriteriaLoader.GetResultColumnOrRow(Object[] row, IResultTransformer customResultTransformer, IDataReader rs, ISessionImplementor session)
at NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies)
at NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies)
at NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters)
at NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters)
at NHibernate.Loader.Criteria.CriteriaLoader.List(ISessionImplementor session)
at NHibernate.Impl.SessionImpl.List(CriteriaImpl criteria, IList results)
at NHibernate.Impl.CriteriaImpl.List(IList results)
at NHibernate.Impl.CriteriaImpl.List()
从查询中可以看出，别名使用两个值（y0_和y1_），但不知怎的，它正在寻找y2_。 我认为这是因为我在这里使用了一个它无法处理的嵌套投影，或者我是否已经错误地实现或调用了投影？
任何帮助或替代建议都会很棒。我意识到这可以通过多种方式使用HQL等来完成，但对使用QueryOver
特别感兴趣提前致谢
答案 0 :(得分：1)
男生错误。
投影的GetTypes方法应该返回投影结果中涉及的类型。我正在返回所涉及领域的类型。
应该是这样的：
public override IType[] GetTypes(ICriteria criteria, ICriteriaQuery criteriaQuery)
{
return new IType[] { NHibernateUtil.Int32 };
}
希望这能节省一些时间