LinqToSQL下實(shí)現(xiàn)動(dòng)態(tài)表名的映射前段時(shí)間，在博客園里看到有位朋友，問(wèn)如何實(shí)現(xiàn)在動(dòng)態(tài)表名。我們都知道，把一個(gè)實(shí)體類(lèi)映謝到表里，應(yīng)當(dāng)這樣寫(xiě)：

[Table(Name=“User“)]

classUser

{

[Column]

publicintID;

[Column]

publicstringName;

}

很明顯，這里的表名是寫(xiě)死的，有些時(shí)候，我們可能要依據(jù)不同的狀況實(shí)現(xiàn)不同的表名里加個(gè)前綴或者后綴，例如：

tt_User，aa_User，User1、User2。

分析問(wèn)題

要解決這個(gè)問(wèn)題，首先我們就要明白一個(gè)問(wèn)題，DataContext是如何將實(shí)體到表的映射的，事實(shí)上，它是例用MappingSource供應(yīng)的信息來(lái)進(jìn)展映射的。要解決上面的問(wèn)題，我就是需要重新構(gòu)一個(gè)繼承于MappingSource的類(lèi)。

解決問(wèn)題

代碼如下：

usingSystem;

usingSystem.Collections.Generic;

usingSystem.Data.Linq;

usingSystem.Data.Linq.Mapping;

usingSystem.Diagnostics;

usingSystem.Globalization;

usingSystem.Linq;

usingSystem.Reflection;

usingSystem.Text;

usingSystem.Xml.Schema;

namespaceALinq.Mapping

{

classDynamicMappingSource:MappingSource

{

classDynamicAttributedMetaModel:MetaModel

{

privateMetaModelsource;

privateconststringTypeName=“System.Data.Linq.Mapping.AttributedMetaModel“;

privateDynamicMappingSourcemappingSource;

internalDynamicAttributedMetaModel(MappingSourcemappingSource,TypecontextType)

{

this.mappingSource=(DynamicMappingSource)mappingSource;

varbf=BindingFlags.NonPublic|BindingFlags.Instance|BindingFlags.CreateInstance;

varargs=newobject[]{mappingSource,contextType};

source=typeof(DataContext).Assembly.CreateInstance(TypeName,false,bf,null,

args,CultureInfo.CurrentCulture,null)asMetaModel;

Debug.Assert(source!=null);

}

publicoverrideMetaTableGetTable(TyperowType)

{

if(mappingSource.GetMetaTableName!=null)

{

vartypeName=“System.Data.Linq.Mapping.AttributedMetaTable“;

varbf=BindingFlags.NonPublic|BindingFlags.Instance|BindingFlags.CreateInstance;

varattribute=newTableAttribute{Name=mappingSource.GetMetaTableName(rowType)};

varargs=newobject[]{source,attribute,rowType};

varmetaTable=typeof(DataContext).Assembly.CreateInstance(typeName,false,bf,null,

args,CultureInfo.CurrentCulture,null)asMetaTable;

returnmetaTable;

}

returnsource.GetTable(rowType);

}

publicoverrideMetaFunctionGetFunction(MethodInfomethod)

{

returnsource.GetFunction(method);

}

publicoverrideIEnumerableGetTables()

{

returnsource.GetTables();

}publicoverrideIEnumerableGetFunctions()

{

returnsource.GetFunctions();

}

publicoverrideMetaTypeGetMetaType(Typetype)

{

returnsource.GetMetaType(type);

}

publicoverrideMappingSourceMappingSource

{

get{returnsource.MappingSource;}

}

publicoverrideTypeContextType

{

get{returnsource.ContextType;}

}

publicoverridestringDatabaseName

{

get{returnsource.DatabaseName;}

}

publicoverrideTypeProviderType

{

get{returnsource.ProviderType;}

}

}

publicFuncGetMetaTableName;

protectedoverrideMetaModelCreateModel(TypedataContextType)

{

if(dataContextType==null)

{

thrownewArgumentNullException(“dataContextType“);

}

returnnewDynamicAttributedMetaModel(this,dataContextType);

}

}

[Table(Name=“User“)]

classUser

{

[Column]

publicintID;

[Column]

publicstringName;

}

classProgram

{

staticvoidMain(string[]args)

{

varmappingSource=newDynamicMappingSource();

inti=0;

mappingSource.GetMetaTableName=delegate(Typetype)

{

varatt=type.GetCustomAttributes(typeof(TableAttribute),true).Single()

asTableAttribute;

Debug.Assert(att!=null);

returnatt.Name+i;

};

varconstr=@“DataSource=NOTEBOOKSQLEXPRESS;InitialCatalog=DemoDataContext;IntegratedSecurity=True“;

v