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LLBL Gen + Entity Framework 程序设计入门

2013-07-22 20:42 232 查看

EntityFramework推出有好几年，除了微软的VisualStudio可以做实体框架开发外，第三方的开发工具如LLBLGen，
DevartEntityDeveloper也可以用来做设计开发。
设计数据库表Configuration，它的SQL定义如下

IFOBJECT_ID('dbo.Configuration')ISNOTNULL
DROPTABLEdbo.Configuration
GO

CREATETABLEdbo.Configuration
(
RecnumINTIDENTITYNOTNULL,
MasterKeyNVARCHAR(50)NOTNULL,
DescriptionTEXTNULL,
RemarkNVARCHAR(400)NULL,
CONSTRAINTPK_X_ConfigPRIMARYKEY(MasterKey)
)
GO

TheEntity"FileType"containsfield"FileType"whichhasthesamenameasitscontainingelement,somethingwhichisn'tsupportedbytheEntityFramework

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.csharpcode.lnum{color:#606060;}映射的实体名字段中，不能包含与实体名称一样的字段。比如，我有一个FileType的表，映射到FileType实体，它包含一个FileType的主键字段，自动生成映射时，这是不允许的。
清除这个错误之后，按F7生成代码，用VisualStudio2012打开项目，如下图所示

LLBLGen代码生成器帮忙我们生成EntityFramework所需要的edmx文件，类型定义和DataContext类型。
来看一下生成的类型定义代码，Configuration表映射的实体类型Configuration实体，它的代码如下

///<summary>Classwhichrepresentstheentity'Configuration'.</summary>
[Serializable]
[DataContract(IsReference=true)]
[EdmEntityType(NamespaceName="Entity35Model",Name="Configuration")]
publicpartialclassConfiguration:CommonEntityBase
{
#regionClassMemberDeclarations
privateSystem.String_description;
privateSystem.String_masterKey;
privateSystem.Int32_recnum;
privateSystem.String_remark;
#endregion

#regionExtensibilityMethodDefinitions
partialvoidOnDescriptionChanging(System.Stringvalue);
partialvoidOnDescriptionChanged();
partialvoidOnMasterKeyChanging(System.Stringvalue);
partialvoidOnMasterKeyChanged();
partialvoidOnRecnumChanging(System.Int32value);
partialvoidOnRecnumChanged();
partialvoidOnRemarkChanging(System.Stringvalue);
partialvoidOnRemarkChanged();
#endregion

///<summary>Initializesanewinstanceofthe<seecref="Configuration"/>class.</summary>
publicConfiguration():base()
{
}

///<summary>Factorymethodtocreateanewinstanceoftheentitytype'Configuration'</summary>
///<paramname="masterKeyValue">Theinitialvalueforthefield'MasterKey'</param>
///<paramname="recnumValue">Theinitialvalueforthefield'Recnum'</param>
publicstaticConfigurationCreateConfiguration(System.StringmasterKeyValue,System.Int32recnumValue)
{
vartoReturn=newConfiguration();
toReturn.MasterKey=masterKeyValue;
toReturn.Recnum=recnumValue;
returntoReturn;
}

#regionClassPropertyDeclarations
///<summary>GetsorsetstheDescriptionfield.</summary>
[DataMember]
[EdmScalarProperty()]
publicSystem.StringDescription
{
get{return_description;}
set
{
OnDescriptionChanging(value);
this.ReportPropertyChanging("Description");
_description=SetValidValue(value,true);
this.ReportPropertyChanged("Description");
OnDescriptionChanged();
}
}

///<summary>GetsorsetstheMasterKeyfield.</summary>
[DataMember]
[EdmScalarProperty(EntityKeyProperty=true,IsNullable=false)]
publicSystem.StringMasterKey
{
get{return_masterKey;}
set
{
if(_masterKey==value)
{
return;
}
OnMasterKeyChanging(value);
this.ReportPropertyChanging("MasterKey");
_masterKey=SetValidValue(value,false);
this.ReportPropertyChanged("MasterKey");
OnMasterKeyChanged();
}
}

///<summary>GetsorsetstheRecnumfield.</summary>
[DataMember]
[EdmScalarProperty(IsNullable=false)]
publicSystem.Int32Recnum
{
get{return_recnum;}
privateset
{
OnRecnumChanging(value);
this.ReportPropertyChanging("Recnum");
_recnum=SetValidValue(value);
this.ReportPropertyChanged("Recnum");
OnRecnumChanged();
}
}

///<summary>GetsorsetstheRemarkfield.</summary>
[DataMember]
[EdmScalarProperty()]
publicSystem.StringRemark
{
get{return_remark;}
set
{
OnRemarkChanging(value);
this.ReportPropertyChanging("Remark");
_remark=SetValidValue(value,true);
this.ReportPropertyChanged("Remark");
OnRemarkChanged();
}
}

#endregion
}

LLBLGen让生成的实体类型派生于CommonEntityBase，这个类型派生于EntityObject，定义如下

///<summary>Classwhichisthecommonbaseclassforallgeneratedentityclasses.</summary>
///<remarks>Asallnon-subtypeentityclassesderivefromthisclass,useapartialclassofthisclasstoimplementcodewhichissharedamongallgeneratedentityclasses</remarks>
[DataContract(IsReference=true)]
[Serializable]
publicabstractpartialclassCommonEntityBase:EntityObject
{
#regionClassExtensibilityMethods
///<summary>Methodcalledfromtheconstructor</summary>
partialvoidOnCreated();
#endregion

///<summary>Initializesanewinstanceofthe<seecref="CommonEntityBase"/>class.</summary>
protectedCommonEntityBase():base()
{
OnCreated();
}

}

可以在这个类型中，创建一些公共的方法以方便在生成的实体类型中使用。
LLBLGen为实体框架的实体的每个属性添加了二个跟踪机制方法：Changing和Changed方法。这里可以写我们实体的业务逻辑。比如在采购单中，用户改变单价时，自动重新计算金额(金额=数量*单价)。
以备注属性为例子，请看下面的代码

///<summary>GetsorsetstheRemarkfield.</summary>
[DataMember]
[EdmScalarProperty()]
publicSystem.StringRemark
{
get{return_remark;}
set
{
OnRemarkChanging(value);
this.ReportPropertyChanging("Remark");
_remark=SetValidValue(value,true);
this.ReportPropertyChanged("Remark");
OnRemarkChanged();
}
}

partialvoidOnRemarkChanging(System.Stringvalue);
partialvoidOnRemarkChanged();

这二个方法都是partial方法，如果我们没有定义方法体，则编译时，它会被忽略。partial方法是C#3.0才引入的特性，为方便代码生成器与开发人员之间的合作更紧密。试想一下，怎么在不修改代码生成器生成的方法的情况下，添加自定义的业务代码到类型的方法，属性中去呢？答案是partial方法。
同时，因为生成的实体类型已经加了partial关键字，所以我们可以再加入一个同名的实体类型，用来写业务逻辑，而不更改代码生成器自动生成的代码。
最后，写一个测试方法，让它读取系统的配置表Configuration中的数据：

publicstaticvoidMain(string[]args)
{
Entity35DataContextentity35DataContext=newEntity35DataContext();
varconfigurations=fromiteminentity35DataContext.Configurations
selectitem;

foreach(vardbDataRecordinconfigurations)
{
stringcompanyCode=dbDataRecord.MasterKey;

}
}

一行代码即可完成数据库的读取，而且读取的数据是强类型，非常方便。
一般在入门例子中，容易出错的地方是配置文件的内容，来看一下App.config文件的内容：

<?xmlversion="1.0"encoding="utf-8"?>
<configuration>
<connectionStrings>
<!--pleaseadjusttheconnectionstringembeddedintheelementbelowtotargetthepropercatalog/serverusingtheproperuser/passwordcombination-->
<addname="ConnectionString.SQLServer(SqlClient)"connectionString="metadata=res://*/Entity35.csdl|res://*/Entity35.ssdl|res://*/Entity35.msl;provider=System.Data.SqlClient;providerconnectionstring="datasource=.\sqlexpress;initialcatalog=Framework;integratedsecurity=SSPI;persistsecurityinfo=False;packetsize=4096""providerName="System.Data.EntityClient"/>
</connectionStrings>
</configuration>

///<summary>Initializesanewinstanceofthe<seecref="Entity35DataContext"/>classusingtheconnectionstringfoundinthe'Entity35'sectionoftheapplicationconfigurationfile.</summary>
publicEntity35DataContext():base("name=ConnectionString.SQLServer(SqlClient)","Entity35Entities")
{
Initialize();
}

///<summary>Initializesanewinstanceofthe<seecref="Entity35DataContext"/>class</summary>
publicEntity35DataContext(stringconnectionString):base(connectionString,"Entity35Entities")
{
Initialize();
}

///<summary>Initializesanewinstanceofthe<seecref="Entity35DataContext"/>class</summary>
///<paramname="connection">ReadytouseEntityConnectionobjecttobeusedwiththiscontext</param>
publicEntity35DataContext(System.Data.EntityClient.EntityConnectionconnection):base(connection,"Entity35Entities")
{
Initialize();
}

EntityFramework的连接字符串与经常写的SQLServer的SqlConnection的字符串有所区别，要指定依据edmx生成的三个文件的位置，因为edmx文件的BuildAction为EntityDeploy，所以它会被嵌入到生成的程序集中。

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.csharpcode.lnum{color:#606060;}用.NETReflector载入生成的实体程序集，查看它的资源文件，如上图所示，三个资源文件被嵌入在程序集中。

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