婶可忍叔不可忍的AutoMapper,你还用吗?
<h2 id="automapper是让人又爱又恨的项目">AutoMapper是让人又爱又恨的项目</h2><blockquote>
<ul>
<li>爱它是因为它解决了一些问题,很多项目都有用,下载量很大,受众很广。</li>
<li>恨它是因为它诸多反人类的设计。</li>
<li>为此本人开源项目PocoEmit对标AutoMapper。</li>
</ul>
</blockquote>
<h2 id="1-automapper反人类设计">1. AutoMapper反人类设计</h2>
<h3 id="11-automapper注册代码">1.1 AutoMapper注册代码</h3>
<pre><code class="language-csharp">services.AddAutoMapper(cfg => cfg.CreateMap<User, UserDTO>());
</code></pre>
<p>User和UserDTO除了类名不一样,其他都一样,怎么看这行代码都多余。<br>
需要转化的类型越多,多余的代码就越多。<br>
类型转化不应该就是个静态方法吗?而且AutoMapper注册却依赖容器,Mapper对象也是从容器获取。<br>
本人觉得AutoMapper设计的太反人类了。</p>
<h3 id="12-pocoemit对于大部分转化是不需要手动配置">1.2 PocoEmit对于大部分转化是不需要手动配置</h3>
<blockquote>
<ul>
<li>PocoEmit可以轻松的定义静态实例。</li>
<li>PocoEmit静态实例可以用来定义静态委托字段,当静态方法用。</li>
</ul>
</blockquote>
<pre><code class="language-csharp">UserDTO dto = PocoEmit.Mapper.Default.Convert<User, UserDTO>(new User());
</code></pre>
<pre><code class="language-csharp">public static readonly Func<User, UserDTO> UserDTOConvert = PocoEmit.Mapper.Default.GetConvertFunc<User, UserDTO>();
</code></pre>
<h2 id="2-automapper的性能差强人意">2. AutoMapper的性能差强人意</h2>
<h3 id="21-以下是automapper官网例子与pocoemitmapper的对比">2.1 以下是AutoMapper官网例子与PocoEmit.Mapper的对比</h3>
<blockquote>
<ul>
<li>Customer转化为CustomerDTO(嵌套多个子对象、数组及列表)。</li>
<li>Auto是执行AutoMapper的IMapper.Map方法。</li>
<li>Poco是执行PocoEmit.Mapper的IMapper.Convert方法。</li>
<li>PocoFunc是执行PocoEmit.Mapper生成的委托。</li>
</ul>
</blockquote>
<table>
<thead>
<tr>
<th>Method</th>
<th style="text-align: right">Mean</th>
<th style="text-align: right">Error</th>
<th style="text-align: right">StdDev</th>
<th style="text-align: right">Median</th>
<th style="text-align: right">Ratio</th>
<th style="text-align: right">RatioSD</th>
<th style="text-align: right">Gen0</th>
<th style="text-align: right">Allocated</th>
<th style="text-align: right">Alloc Ratio</th>
</tr>
</thead>
<tbody>
<tr>
<td>Auto</td>
<td style="text-align: right">89.30 ns</td>
<td style="text-align: right">1.006 ns</td>
<td style="text-align: right">1.118 ns</td>
<td style="text-align: right">90.17 ns</td>
<td style="text-align: right">1.46</td>
<td style="text-align: right">0.03</td>
<td style="text-align: right">0.0260</td>
<td style="text-align: right">448 B</td>
<td style="text-align: right">1.08</td>
</tr>
<tr>
<td>Poco</td>
<td style="text-align: right">61.31 ns</td>
<td style="text-align: right">1.036 ns</td>
<td style="text-align: right">1.194 ns</td>
<td style="text-align: right">61.25 ns</td>
<td style="text-align: right">1.00</td>
<td style="text-align: right">0.03</td>
<td style="text-align: right">0.0241</td>
<td style="text-align: right">416 B</td>
<td style="text-align: right">1.00</td>
</tr>
<tr>
<td>PocoFunc</td>
<td style="text-align: right">42.56 ns</td>
<td style="text-align: right">0.066 ns</td>
<td style="text-align: right">0.073 ns</td>
<td style="text-align: right">42.56 ns</td>
<td style="text-align: right">0.69</td>
<td style="text-align: right">0.01</td>
<td style="text-align: right">0.0223</td>
<td style="text-align: right">384 B</td>
<td style="text-align: right">0.92</td>
</tr>
</tbody>
</table>
<blockquote>
<ul>
<li>Auto耗时比Poco多50%左右。</li>
<li>Auto耗时是PocoFunc的两倍多。</li>
</ul>
</blockquote>
<h3 id="22-能不能用automapper生成委托来提高性能呢">2.2 能不能用AutoMapper生成委托来提高性能呢</h3>
<blockquote>
<ul>
<li>既可以说能也可以说不能。</li>
<li>说能是因为AutoMapper确实提供了该功能。</li>
<li>说不能是因为AutoMapper没打算给用户用。</li>
</ul>
</blockquote>
<h3 id="221-automapper生成委托有点麻烦">2.2.1 AutoMapper生成委托有点麻烦</h3>
<pre><code class="language-csharp">var configuration = _auto.ConfigurationProvider.Internal();
var mapRequest = new MapRequest(new TypePair(typeof(Customer), typeof(CustomerDTO)));
Func<Customer, CustomerDTO, ResolutionContext, CustomerDTO> autoFunc = configuration.GetExecutionPlan<Customer, CustomerDTO>(mapRequest);
</code></pre>
<p>作为对比PocoEmit.Mapper就简单的多了</p>
<pre><code class="language-csharp">Func<Customer, CustomerDTO> pocoFunc = PocoEmit.Mapper.Default.GetConvertFunc<Customer, CustomerDTO>();
</code></pre>
<h3 id="222-调用automapper生成的委托更麻烦">2.2.2 调用AutoMapper生成的委托更麻烦</h3>
<blockquote>
<ul>
<li>参数ResolutionContext没有公开的构造函数,也找不到公开的实例。</li>
<li>只能通过反射获得ResolutionContext的实例。</li>
</ul>
</blockquote>
<pre><code class="language-csharp">var field = typeof(AutoMapper.Mapper).GetField("_defaultContext", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
ResolutionContext resolutionContext = field.GetValue(_auto) as ResolutionContext;
</code></pre>
<h3 id="223-加入automapper生成委托再对比一下">2.2.3 加入AutoMapper生成委托再对比一下</h3>
<table>
<thead>
<tr>
<th>Method</th>
<th style="text-align: right">Mean</th>
<th style="text-align: right">Error</th>
<th style="text-align: right">StdDev</th>
<th style="text-align: right">Median</th>
<th style="text-align: right">Ratio</th>
<th style="text-align: right">RatioSD</th>
<th style="text-align: right">Gen0</th>
<th style="text-align: right">Allocated</th>
<th style="text-align: right">Alloc Ratio</th>
</tr>
</thead>
<tbody>
<tr>
<td>Auto</td>
<td style="text-align: right">89.30 ns</td>
<td style="text-align: right">1.006 ns</td>
<td style="text-align: right">1.118 ns</td>
<td style="text-align: right">90.17 ns</td>
<td style="text-align: right">1.46</td>
<td style="text-align: right">0.03</td>
<td style="text-align: right">0.0260</td>
<td style="text-align: right">448 B</td>
<td style="text-align: right">1.08</td>
</tr>
<tr>
<td>AutoFunc</td>
<td style="text-align: right">56.04 ns</td>
<td style="text-align: right">0.103 ns</td>
<td style="text-align: right">0.119 ns</td>
<td style="text-align: right">56.03 ns</td>
<td style="text-align: right">0.91</td>
<td style="text-align: right">0.02</td>
<td style="text-align: right">0.0260</td>
<td style="text-align: right">448 B</td>
<td style="text-align: right">1.08</td>
</tr>
<tr>
<td>Poco</td>
<td style="text-align: right">61.31 ns</td>
<td style="text-align: right">1.036 ns</td>
<td style="text-align: right">1.194 ns</td>
<td style="text-align: right">61.25 ns</td>
<td style="text-align: right">1.00</td>
<td style="text-align: right">0.03</td>
<td style="text-align: right">0.0241</td>
<td style="text-align: right">416 B</td>
<td style="text-align: right">1.00</td>
</tr>
<tr>
<td>PocoFunc</td>
<td style="text-align: right">42.56 ns</td>
<td style="text-align: right">0.066 ns</td>
<td style="text-align: right">0.073 ns</td>
<td style="text-align: right">42.56 ns</td>
<td style="text-align: right">0.69</td>
<td style="text-align: right">0.01</td>
<td style="text-align: right">0.0223</td>
<td style="text-align: right">384 B</td>
<td style="text-align: right">0.92</td>
</tr>
</tbody>
</table>
<blockquote>
<ul>
<li>AutoMapper生成委托确实也快了不少。</li>
<li>从百分比来看即使不生成委托,AutoMapper也慢不了多少？没有数量级的区别,能忍? --- 反问句</li>
</ul>
</blockquote>
<h3 id="23-简单类型转化对比">2.3 简单类型转化对比</h3>
<blockquote>
<ul>
<li>User转UserDTO,只有两个简单属性</li>
</ul>
</blockquote>
<table>
<thead>
<tr>
<th>Method</th>
<th style="text-align: right">Mean</th>
<th style="text-align: right">Error</th>
<th style="text-align: right">StdDev</th>
<th style="text-align: right">Ratio</th>
<th style="text-align: right">Gen0</th>
<th style="text-align: right">Allocated</th>
<th style="text-align: right">Alloc Ratio</th>
</tr>
</thead>
<tbody>
<tr>
<td>Auto</td>
<td style="text-align: right">35.436 ns</td>
<td style="text-align: right">0.0455 ns</td>
<td style="text-align: right">0.0505 ns</td>
<td style="text-align: right">1.57</td>
<td style="text-align: right">0.0019</td>
<td style="text-align: right">32 B</td>
<td style="text-align: right">0.50</td>
</tr>
<tr>
<td>AutoFunc</td>
<td style="text-align: right">4.159 ns</td>
<td style="text-align: right">0.0847 ns</td>
<td style="text-align: right">0.0906 ns</td>
<td style="text-align: right">0.18</td>
<td style="text-align: right">0.0019</td>
<td style="text-align: right">32 B</td>
<td style="text-align: right">0.50</td>
</tr>
<tr>
<td>Poco</td>
<td style="text-align: right">22.607 ns</td>
<td style="text-align: right">0.1754 ns</td>
<td style="text-align: right">0.1801 ns</td>
<td style="text-align: right">1.00</td>
<td style="text-align: right">0.0037</td>
<td style="text-align: right">64 B</td>
<td style="text-align: right">1.00</td>
</tr>
<tr>
<td>PocoFunc</td>
<td style="text-align: right">3.818 ns</td>
<td style="text-align: right">0.0176 ns</td>
<td style="text-align: right">0.0180 ns</td>
<td style="text-align: right">0.17</td>
<td style="text-align: right">0.0019</td>
<td style="text-align: right">32 B</td>
<td style="text-align: right">0.50</td>
</tr>
</tbody>
</table>
<blockquote>
<ul>
<li>Auto耗时是AutoFunc差不多十倍,差出一个数量级了(回答了前面的反问)</li>
<li>AutoFunc耗时比PocoFunc稍多,这说明AutoMapper复杂类型转化性能非常不好,简单类型转化可能还能凑合</li>
<li>关键是性能好生成的委托AutoMapper不给用啊,“婶可忍叔不可忍”啊!</li>
</ul>
</blockquote>
<h2 id="3-automapper生成的代码能通过代码审核吗">3. AutoMapper生成的代码能通过代码审核吗?</h2>
<h3 id="31-automapper官网那个例子生成以下代码">3.1 AutoMapper官网那个例子生成以下代码</h3>
<pre><code class="language-csharp">T __f<T>(System.Func<T> f) => f();
CustomerDTO _autoMap(Customer source, CustomerDTO destination, ResolutionContext context)
{
return (source == null) ?
(destination == null) ? (CustomerDTO)null : destination :
__f(() => {
CustomerDTO typeMapDestination = null;
typeMapDestination = destination ?? new CustomerDTO();
try
{
typeMapDestination.Id = source.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination.Name = source.Name;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
Address resolvedValue = null;
Address mappedValue = null;
resolvedValue = source.Address;
mappedValue = (resolvedValue == null) ? (Address)null :
((Func<Address, Address, ResolutionContext, Address>)((
Address source_1,
Address destination_1,
ResolutionContext context) => //Address
(source_1 == null) ?
(destination_1 == null) ? (Address)null : destination_1 :
__f(() => {
Address typeMapDestination_1 = null;
typeMapDestination_1 = destination_1 ?? new Address();
try
{
typeMapDestination_1.Id = source_1.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_1.Street = source_1.Street;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_1.City = source_1.City;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_1.Country = source_1.Country;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination_1;
})))
.Invoke(
resolvedValue,
(destination == null) ? (Address)null :
typeMapDestination.Address,
context);
typeMapDestination.Address = mappedValue;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
Address resolvedValue_1 = null;
AddressDTO mappedValue_1 = null;
resolvedValue_1 = source.HomeAddress;
mappedValue_1 = (resolvedValue_1 == null) ? (AddressDTO)null :
((Func<Address, AddressDTO, ResolutionContext, AddressDTO>)((
Address source_2,
AddressDTO destination_2,
ResolutionContext context) => //AddressDTO
(source_2 == null) ?
(destination_2 == null) ? (AddressDTO)null : destination_2 :
__f(() => {
AddressDTO typeMapDestination_2 = null;
typeMapDestination_2 = destination_2 ?? new AddressDTO();
try
{
typeMapDestination_2.Id = source_2.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.City = source_2.City;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.Country = source_2.Country;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination_2;
})))
.Invoke(
resolvedValue_1,
(destination == null) ? (AddressDTO)null :
typeMapDestination.HomeAddress,
context);
typeMapDestination.HomeAddress = mappedValue_1;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
Address[] resolvedValue_2 = null;
AddressDTO[] mappedValue_2 = null;
resolvedValue_2 = source.Addresses;
mappedValue_2 = (resolvedValue_2 == null) ?
Array.Empty<AddressDTO>() :
__f(() => {
AddressDTO[] destinationArray = null;
int destinationArrayIndex = default;
destinationArray = new AddressDTO;
destinationArrayIndex = default(int);
int sourceArrayIndex = default;
Address sourceItem = null;
sourceArrayIndex = default(int);
while (true)
{
if ((sourceArrayIndex < resolvedValue_2.Length))
{
sourceItem = resolvedValue_2;
destinationArray = ((Func<Address, AddressDTO, ResolutionContext, AddressDTO>)((
Address source_2,
AddressDTO destination_2,
ResolutionContext context) => //AddressDTO
(source_2 == null) ?
(destination_2 == null) ? (AddressDTO)null : destination_2 :
__f(() => {
AddressDTO typeMapDestination_2 = null;
typeMapDestination_2 = destination_2 ?? new AddressDTO();
try
{
typeMapDestination_2.Id = source_2.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.City = source_2.City;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.Country = source_2.Country;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination_2;
})))
.Invoke(
sourceItem,
(AddressDTO)null,
context);
sourceArrayIndex++;
}
else
{
goto LoopBreak;
}
}
LoopBreak:;
return destinationArray;
});
typeMapDestination.Addresses = mappedValue_2;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
List<Address> resolvedValue_3 = null;
List<AddressDTO> mappedValue_3 = null;
resolvedValue_3 = source.WorkAddresses;
mappedValue_3 = (resolvedValue_3 == null) ?
new List<AddressDTO>() :
__f(() => {
List<AddressDTO> collectionDestination = null;
List<AddressDTO> passedDestination = null;
passedDestination = (destination == null) ? (List<AddressDTO>)null :
typeMapDestination.WorkAddresses;
collectionDestination = passedDestination ?? new List<AddressDTO>();
collectionDestination.Clear();
List<Address>.Enumerator enumerator = default;
Address item = null;
enumerator = resolvedValue_3.GetEnumerator();
try
{
while (true)
{
if (enumerator.MoveNext())
{
item = enumerator.Current;
collectionDestination.Add(((Func<Address, AddressDTO, ResolutionContext, AddressDTO>)((
Address source_2,
AddressDTO destination_2,
ResolutionContext context) => //AddressDTO
(source_2 == null) ?
(destination_2 == null) ? (AddressDTO)null : destination_2 :
__f(() => {
AddressDTO typeMapDestination_2 = null;
typeMapDestination_2 = destination_2 ?? new AddressDTO();
try
{
typeMapDestination_2.Id = source_2.Id;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.City = source_2.City;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
try
{
typeMapDestination_2.Country = source_2.Country;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination_2;
})))
.Invoke(
item,
(AddressDTO)null,
context));
}
else
{
goto LoopBreak_1;
}
}
LoopBreak_1:;
}
finally
{
enumerator.Dispose();
}
return collectionDestination;
});
typeMapDestination.WorkAddresses = mappedValue_3;
}
catch (Exception ex)
{
throw TypeMapPlanBuilder.MemberMappingError(
ex,
default(PropertyMap)/*NOTE: Provide the non-default value for the Constant!*/);
}
return typeMapDestination;
});
}
</code></pre>
<h3 id="32-以下是pocoemitmapper生成的代码">3.2 以下是PocoEmit.Mapper生成的代码</h3>
<pre><code class="language-csharp">CustomerDTO _pocoConvert(Customer source)
{
CustomerDTO dest = null;
if ((source != (Customer)null))
{
dest = new CustomerDTO();
Address member0 = null;
Address member1 = null;
Address[] member2 = null;
List<Address> member3 = null;
dest.Id = source.Id;
dest.Name = source.Name;
member0 = source.Address;
if ((member0 != null))
{
dest.Address = member0;
}
member1 = source.HomeAddress;
if ((member1 != null))
{
// { The block result will be assigned to `dest.HomeAddress`
AddressDTO dest_1 = null;
if ((member1 != (Address)null))
{
dest_1 = new AddressDTO();
dest_1.Id = member1.Id;
dest_1.City = member1.City;
dest_1.Country = member1.Country;
}
dest.HomeAddress = dest_1;
// } end of block assignment;
}
member2 = source.Addresses;
if ((member2 != null))
{
// { The block result will be assigned to `dest.Addresses`
int count = default;
AddressDTO[] dest_2 = null;
int index = default;
Address sourceItem = null;
count = member2.Length;
dest_2 = new AddressDTO;
index = 0;
while (true)
{
if ((index < count))
{
sourceItem = member2;
// { The block result will be assigned to `dest_2`
AddressDTO dest_3 = null;
if ((sourceItem != (Address)null))
{
dest_3 = new AddressDTO();
dest_3.Id = sourceItem.Id;
dest_3.City = sourceItem.City;
dest_3.Country = sourceItem.Country;
}
dest_2 = dest_3;
// } end of block assignment
index++;
}
else
{
goto forLabel;
}
}
forLabel:;
dest.Addresses = dest_2;
// } end of block assignment;
}
member3 = source.WorkAddresses;
if ((member3 != null))
{
// { The block result will be assigned to `dest.WorkAddresses`
List<AddressDTO> dest_4 = null;
dest_4 = new List<AddressDTO>(member3.Count);
dest_4;
int index_1 = default;
int len = default;
index_1 = 0;
len = member3.Count;
while (true)
{
if ((index_1 < len))
{
Address sourceItem_1 = null;
AddressDTO destItem = null;
sourceItem_1 = member3;
// { The block result will be assigned to `destItem`
AddressDTO dest_5 = null;
if ((sourceItem_1 != (Address)null))
{
dest_5 = new AddressDTO();
dest_5.Id = sourceItem_1.Id;
dest_5.City = sourceItem_1.City;
dest_5.Country = sourceItem_1.Country;
}
destItem = dest_5;
// } end of block assignment;
dest_4.Add(destItem);
index_1++;
}
else
{
goto forLabel_1;
}
}
forLabel_1:;
dest.WorkAddresses = dest_4;
// } end of block assignment;
}
CustomerConvertBench.ConvertAddressCity(
source,
dest);
}
return dest;
}
</code></pre>
<h3 id="33-简单对比如下">3.3 简单对比如下</h3>
<blockquote>
<ul>
<li>AutoMapper生成代码三百多行,PocoEmit.Mapper一百多行,AutoMapper代码量是两倍以上</li>
<li>AutoMapper生成大量try catch,哪怕是int对int赋值也要try</li>
<li>AutoMapper用迭代器Enumerator访问列表,PocoEmit.Mapper用索引器</li>
<li>AutoMapper这些区别应该是导致性能差的部分原因</li>
</ul>
</blockquote>
<h3 id="34-如何获取automapper生成的代码">3.4 如何获取AutoMapper生成的代码</h3>
<pre><code class="language-csharp">LambdaExpression expression = _auto.ConfigurationProvider.BuildExecutionPlan(typeof(Customer), typeof(CustomerDTO));
</code></pre>
<h4 id="341-如果要查看更可读的代码推荐使用fastexpressioncompiler">3.4.1 如果要查看更可读的代码推荐使用FastExpressionCompiler</h4>
<blockquote>
<ul>
<li>可以使用nuget安装</li>
<li>前面的例子就是使用FastExpressionCompiler再手动整理了一下</li>
</ul>
</blockquote>
<pre><code class="language-csharp">string code = FastExpressionCompiler.ToCSharpPrinter.ToCSharpString(expression);
</code></pre>
<h4 id="342-pocoemit获取生成代码更简单">3.4.2 PocoEmit获取生成代码更简单</h4>
<pre><code class="language-csharp">Expression<Func<Customer, CustomerDTO>> expression =PocoEmit.Mapper.Default.BuildConverter<Customer, CustomerDTO>();
string code = FastExpressionCompiler.ToCSharpPrinter.ToCSharpString(expression);
</code></pre>
<h4 id="343-pocoemit生成代码扩展性">3.4.3 PocoEmit生成代码扩展性</h4>
<blockquote>
<ul>
<li>PocoEmit可以获取委托表达式自己来编译委托</li>
<li>PocoEmit通过PocoEmit.Builders.Compiler.Instance来编译,可以对Instance进行覆盖来扩展</li>
<li>通过实现Compiler类来扩展,只需要重写CompileFunc和CompileAction两个方法</li>
<li>可以使用FastExpressionCompiler来实现Compiler类</li>
</ul>
</blockquote>
<h2 id="4-automapper枚举逻辑问题">4. AutoMapper枚举逻辑问题</h2>
<pre><code class="language-csharp">public enum MyColor
{
None = 0,
Red = 1,
Green = 2,
Blue = 3,
}
ConsoleColor color = ConsoleColor.DarkBlue;
// Red
MyColor autoColor = _auto.Map<ConsoleColor, MyColor>(color);
// None
MyColor pocoColor = PocoEmit.Mapper.Default.Convert<ConsoleColor, MyColor>(color);
</code></pre>
<blockquote>
<ul>
<li>AutoMapper先按枚举名转化,失败再按值转化,不支持的DarkBlue被AutoMapper转化为Red</li>
<li>不同类型的枚举值转化没有意义,定义枚举可以不指定值</li>
<li>AutoMapper这完全是犯了画蛇添足的错误</li>
<li>AutoMapper还有哪些槽点欢迎大家在评论区指出</li>
</ul>
</blockquote>
<h2 id="5-pocoemit可扩展架构">5. PocoEmit可扩展架构</h2>
<h3 id="51-nuget安装pocoemit可获得基础功能">5.1 nuget安装PocoEmit可获得基础功能</h3>
<blockquote>
<ul>
<li>通过PocoEmit可以读写实体的属性</li>
<li>PocoEmit可以通过PocoEmit.Poco转化基础类型和枚举</li>
<li>PocoEmit.Poco支持注册转化表达式</li>
</ul>
</blockquote>
<h3 id="52-nuget安装pocoemitmapper获得更多功能">5.2 nuget安装PocoEmit.Mapper获得更多功能</h3>
<blockquote>
<ul>
<li>PocoEmit.Mapper可以支持PocoEmit.Poco的所有功能</li>
<li>PocoEmit.Mapper可以支持自定义实体类型(不支持集合(含数组、列表及字典)成员)的转化和复制</li>
</ul>
</blockquote>
<h3 id="53-nuget安装pocoemitcollections扩展集合功能">5.3 nuget安装PocoEmit.Collections扩展集合功能</h3>
<blockquote>
<ul>
<li>通过UseCollection扩展方法给PocoEmit.Mapper增加集合功能</li>
<li>扩展后PocoEmit.Mapper支持集合(含数组、列表及字典)的转化和复制</li>
<li>支持实体类型包含集合成员的转化和复制</li>
<li>嫌麻烦的同学可以直接安装PocoEmit.Collections并配置UseCollection</li>
</ul>
</blockquote>
<p>如何使用PocoEmit.Mapper替代AutoMapper请移步看下一篇 https://www.cnblogs.com/xiangji/p/19062936</p>
<p>源码托管地址: https://github.com/donetsoftwork/MyEmit ，也欢迎大家直接查看源码。<br>
gitee同步更新:https://gitee.com/donetsoftwork/MyEmit</p>
<p>如果大家喜欢请动动您发财的小手手帮忙点一下Star。</p><br><br>
来源：https://www.cnblogs.com/xiangji/p/19059979
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