前言:
连接等是使用创建的
DbProviderFactories。
多库。
我正在将DbDataReader映射到实体并具有一些基准:
[0] retrieved 159180 records in 45135 ms
[1] retrieved 159180 records in 45008 ms
[2] retrieved 159180 records in 44814 ms
[3] retrieved 159180 records in 44987 ms
[4] retrieved 159180 records in 44914 ms
[5] retrieved 159180 records in 45224 ms
[6] retrieved 159180 records in 45829 ms
[7] retrieved 159180 records in 60762 ms
[8] retrieved 159180 records in 52128 ms
[9] retrieved 159180 records in 47982 ms
考虑到从Sql Server Management Studio进行查询只需要17秒,这是一个相当长的时间,而且非常糟糕。我的选择语句:
“选择*从tbl_MyTable”
该表包含43个字段,可能未按应有的最佳索引编制。但是,执行全选,我不希望索引会出现问题。所以...这是我在做什么:
定义实体:
public class Concept
{
#region Columns
[DataParameter("ConceptID", DbType.Int32)]
public Int32 ConceptID
{ get; set; }
[DataParameter("ConceptName", DbType.String)]
public string ConceptName
{ get; set; }
[DataParameter("ConceptTypeID", DbType.Int32)]
public Int32 ConceptTypeID
{ get; set; }
[DataParameter("ActiveYN", DbType.Boolean)]
public bool ActiveYN
{ get; set; }
#endregion
}
查询数据读取器:
for (int i = 0; i <= 99; i++)
{
sw.Start();
var results = session.QueryReader<Concept>(
new SqlCommand(command), dr => new Concept());
sw.Stop();
Console.WriteLine("[{0}] retrieved {1} records in {2} ms", i, results.Count(), sw.ElapsedMilliseconds);
sw.Reset();
}
...致电:
Public Function QueryReader(Of TEntity As {Class, New})(ByVal Command As DbCommand, _
ByVal Projection As Func(Of DbDataReader, TEntity)) _
As IEnumerable(Of TEntity)
Dim list As IEnumerable(Of TEntity)
Command.Connection = dataReader.NewConnection
Command.Connection.Open()
Using _reader As DbDataReader = Command.ExecuteReader()
list = _reader.Query(Of TEntity)(Projection).ToList()
End Using
Command.Connection.Close()
Return list
End Function
...和扩展方法
QueryReader<T>
:编辑新的TEntity()的位置-谢谢@Henkpublic static IEnumerable<TEntity> Query<TEntity>(this DbDataReader Reader,
Func<DbDataReader, TEntity> Projection)
where TEntity : class, new()
{
// moving this reflection to another class
Dictionary<string, PropertyInfo> props;
while (Reader.Read())
{
TEntity entity = new TEntity();
if (!entities.TryGetValue(typeof(TEntity).ToString(), out props))
{
// reflection over TEntity
props = (from p in entity.GetType().GetProperties()
from a in p.GetCustomAttributes(typeof(DataParameterAttribute), false)
select p)
.ToDictionary(p => p.Name);
entities.Add(typeof(TEntity).ToString(), props);
}
foreach (KeyValuePair<string, PropertyInfo> field in props)
{
if (null != Reader[field.Key] && Reader[field.Key] != DBNull.Value)
{ field.Value.SetValue(entity, Reader[field.Key], null); }
}
yield return entity;
}
}
关于提高性能的任何建议将不胜感激...
更新
我按照@EtienneT的建议实现了dapper-dot-net-这是检索时间:
[0] retrieved 159180 records in 6874 ms
[1] retrieved 159180 records in 6866 ms
[2] retrieved 159180 records in 6570 ms
[3] retrieved 159180 records in 6785 ms
[4] retrieved 159180 records in 6693 ms
[5] retrieved 159180 records in 6735 ms
[6] retrieved 159180 records in 6627 ms
[7] retrieved 159180 records in 6739 ms
[8] retrieved 159180 records in 6569 ms
[9] retrieved 159180 records in 6666 ms
最佳答案
您是否考虑过像dapper.net这样的微型ORM?
https://github.com/StackExchange/dapper-dot-net
它由StackOverflow的开发人员制作,并将SQL查询直接映射到您的对象。它生成并缓存IL代码,以将SQL结果映射到您的对象。因此,每种类型仅生成一次IL代码。从未使用过它,但是如果您需要性能以将SQL结果映射到.net对象,则它是您需要的库。
关于c# - 如何将DataReader映射到类属性并保持性能?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/6142659/