. NET using SQL in EF, use dynamic Class!

. NET using SQL in EF, use dynamic Class!

Preface

Using the Entity Framework in. NET makes it quick and easy to combine LINQ with a series of additions and deletions to the database. But because EF executes based on the expression of the last generation of common SQL, it performs specific database operations. Based on my experience with EF, I can use EF's interface to quickly develop the operation of adding, deleting and changing. But for the operation of the query, it is best to use EF to invoke SQL to operate.

Problem Presentation

　　　　After calling SQL for a data query in EF, you need to return a list of data of the specified type, which you need to specify at the time of invocation. We will encounter this problem: I just need to look up some simple data, such as query the number of data to meet a certain criteria, and so on, you must create a new type, increase the redundancy of the program.

Solution Solutions

　　　　To implement a method that dynamically generates classes, you can insert property names and property types, and return a type that is available to EF for use.

Implement

　　　　

 //the class is used to define an attribute node, including the name of the property and the type of the property. 
 Public  class   PropertyItem { string   name, type type) { thi S .            Name = name;  this .        Type = type;  public  string  Name {set ; get          public  type type {set ; get  ;} }

　　　　　

//The class is provided with interfaces that dynamically generate types of.
Public classUsertypefactory { Public StaticType Getusertype (paramspropertyitem[] itemList) {TypeBuilder Builder=Createtypebuilder ("mydynamicassembly","MyModule","MyType"); foreach(varIteminchitemList) {Createautoimplementedproperty (builder, item. Name, item.            Type); } Type Resulttype=Builder.            CreateType (); returnResulttype; }        Private StaticTypeBuilder Createtypebuilder (stringAssemblyName,stringModuleName,stringtypeName) {TypeBuilder TypeBuilder=AppDomain. CurrentDomain. DefineDynamicAssembly (NewAssemblyName (AssemblyName), Assemblybuilderaccess.run). DefineDynamicModule (ModuleName).            DefineType (TypeName, typeattributes.public);            Typebuilder.definedefaultconstructor (Methodattributes.public); returnTypeBuilder; }        Private Static voidCreateautoimplementedproperty (TypeBuilder builder,stringPropertyName, Type PropertyType) {            Const stringPrivatefieldprefix ="m_"; Const stringGetterprefix ="get_"; Const stringSetterprefix ="set_"; //define a field.FieldBuilder FieldBuilder =Builder. DefineField (string.            Concat (Privatefieldprefix, PropertyName), PropertyType, fieldattributes.private); //Defining PropertiesPropertyBuilder PropertyBuilder =Builder. DefineProperty (PropertyName, System.Reflection.PropertyAttributes.HasDefault, PropertyType,NULL); //properties of getter and setter attributesMethodAttributes propertymethodattributes =Methodattributes.public| MethodAttributes.SpecialName |Methodattributes.hidebysig; //Defining Getter MethodsMethodBuilder Gettermethod =Builder. DefineMethod (string.            Concat (Getterprefix, PropertyName), Propertymethodattributes, PropertyType, type.emptytypes); ILGenerator Getterilcode=Gettermethod.getilgenerator ();            Getterilcode.emit (OPCODES.LDARG_0);            Getterilcode.emit (OPCODES.LDFLD, FieldBuilder);            Getterilcode.emit (Opcodes.ret); //Defining Setter MethodsMethodBuilder Settermethod =Builder. DefineMethod (string. Concat (Setterprefix, PropertyName), Propertymethodattributes,NULL,Newtype[] {propertyType}); ILGenerator Setterilcode=Settermethod.getilgenerator ();            Setterilcode.emit (OPCODES.LDARG_0);            Setterilcode.emit (opcodes.ldarg_1);            Setterilcode.emit (OPCODES.STFLD, FieldBuilder);            Setterilcode.emit (Opcodes.ret);            Propertybuilder.setgetmethod (Gettermethod);        Propertybuilder.setsetmethod (Settermethod); }    }

Use

　　　　

 ymsentities entities=new ymsentities();
Dynamicstudentdic= entities. Database.sqlquery (Usertypefactory.getusertype (NewPropertyItem ("ID",typeof(int)),NewPropertyItem ("Num",typeof(string))),"Select ID, Name as num from student");foreach(varUserCountinchstudentdic) {
//Business}

. NET using SQL in EF, use dynamic Class!