Designing Data Tier Components and Passing Data Through Tiers

HowtoDefineaBusinessEntityComponent

{

//Privatefields,toholdthestateoftheProductentity

privateintproductID;

privatestringproductName;

privatestringquantityPerUnit;

privatedecimalunitPrice;

privateshortunitsInStock;

privateshortunitsOnOrder;

privateshortreorderLevel;

//Publicproperties,toexposethestateoftheentity

publicintProductID

{

get{returnproductID;}

set{productID=value;}

}

publicstringProductName

{

get{returnproductName;}

set{productName=value;}

}

publicstringQuantityPerUnit

{

get{returnquantityPerUnit;}

set{quantityPerUnit=value;}

}

publicdecimalUnitPrice

{

get{returnunitPrice;}

set{unitPrice=value;}

}

publicshortUnitsInStock

{

get{returnunitsInStock;}

set{unitsInStock=value;}

}

publicshortUnitsOnOrder

{

get{returnunitsOnOrder;}

set{unitsOnOrder=value;}

}

publicshortReorderLevel

{

get{returnreorderLevel;}

set{reorderLevel=value;}

}

//Methodsandpropertiestoperformlocalizedprocessing

publicvoidIncreaseUnitPriceBy(decimalamount)

{

unitPrice+=amount;

}

publicshortUnitsAboveReorderLevel

{

get{return(short)(unitsInStock-reorderLevel);}

}

publicstringStockStatus

{

get

{

return"Instock:"+unitsInStock+",onorder:"+unitsOnOrder;

}

}

}

HowtoRepresentCollectionsandHierarchiesofDatainaBusinessEntityComponent

{

//Privatefields,toholdtheorderinformation

privateintorderID;

privatestringcustomerID;

privateDateTimeorderDate;

privateDateTimeshippedDate;

//Privatefield,toholdtheorderdetailsinformation

privateDataSetorderDetails;

//Publicproperties,toexposetheorderinformation

publicintOrderID

{

get{returnorderID;}

set{orderID=value;}

}

publicstringCustomerID

{

get{returncustomerID;}

set{customerID=value;}

}

publicDateTimeOrderDate

{

get{returnorderDate;}

set{orderDate=value;}

}

publicDateTimeShippedDate

{

get{returnshippedDate;}

set{shippedDate=value;}

}

//Publicproperty,toexposetheorderdetailsinformation

publicDataSetOrderDetails

{

get{returnorderDetails;}

set{orderDetails=value;}

}

//Additionalmethod,tosimplifyaccesstoorderdetailsinformation

publicboolIsProductOrdered(intproductID)

{

//PrimarykeycolumnmustbedefinedinDataTable

DataRowrow=orderDetails.Tables[0].Rows.Find(productID);

if(row!=null)

returntrue;

else

returnfalse;

}

//Additionalproperty,tosimplifyaccesstoorderdetailsinformation

publicintNumberOfOrderItems

{

get

{

returnorderDetails.Tables[0].Rows.Count;

}

}

}

HowtoBindBusinessEntityComponentstoUser-InterfaceControls

·OrderDALCdalcOrder=newOrderDALC();

·

·//UsedalcOrdertogetanOrderEntityobjectfororderID10248.

·//ThiscodeassumestheOrderDALCclasshasamethodnamedGetOrder(),

·which

·//returnsanOrderEntityobjectforaparticularorderID.

·OrderEntityorder=dalcOrder.GetOrder(10248);

·

·//BindtheOrderIDpropertyoftheOrderEntitytoaTextBoxcontrol.

·textBox1.DataBindings.Add("Text",order,"OrderID");

·

·//BindtheCustomerIDpropertyoftheOrderEntitytoanotherTextBox

·control.

·textBox2.DataBindings.Add("Text",order,"CustomerID");

·

·//BindtheOrderDatepropertyoftheOrderEntitytoaDatePickercontrol.

·dateTimePicker1.DataBindings.Add("Value",order,"OrderDate");

·

·//BindtheShippedDatepropertyoftheOrderEntitytoanotherDatePicker

·control.

·dateTimePicker2.DataBindings.Add("Value",order,"ShippedDate");

·

·//BindtheOrderDetailsDataSetoftheOrderEntitytoaDataGridcontrol.

·//TheDataGriddisplayseachDataRowoftheDataSetinaseparaterowin

·thegrid.

·dataGrid1.DataSource=order.OrderDetails.Tables[0].DefaultView;

//ThiscodeassumestheOrderDALCclasshasamethodnamedUpdateOrder(),

which

//receivesanOrderEntityparameterandupdatestheappropriateentryin

thedatabase

dalcOrder.UpdateOrder(order);

·OrderDALCdalcOrder=newOrderDALC();

·

·//UsedalcOrdertogetanarrayofOrderEntityobjectsforcustomer

·"VINET".

·//ThiscodeassumestheOrderDALCclasshasamethodnamed

·GetOrdersForCustomer(),

·//whichreturnsanarrayofOrderEntityobjectsforaparticular

·customer.

·OrderEntity[]orderEntities=dalcOrder.GetOrdersForCustomer("VINET");

·

·//BindthearraytoaDataGridcontrol.

·dataGrid1.DataSource=orderEntities;

//ThiscodeassumesOrderDALChasamethodnamedUpdateOrders(),which

takesanarray

//ofOrderEntityobjectsandupdatestheappropriateentriesinthe

database.

dalcOrder.UpdateOrders(orderEntities);

HowtoExposeEventsinaBusinessEntityComponent

publicclassEntityEventArgs:EventArgs

{

//Defineeventmembers,toprovideinformationabouttheevent

}

//Defineadelegatespecifyingthesignatureforbusinessentity-related

events

publicdelegatevoidEntityEventHandler(Objectsource,EntityEventArgse);

//DefineacustomEntityclassthatraiseseventswhenthebusinessentity

statechanges

publicclassOrderEntity

{

//Define'before'and'after'eventsforbusinessentitystatechanges

publiceventEntityEventHandlerBeforeChange,AfterChange;

//Privatefields,toholdthebusinessentity'sstate

privateintorderID;

privateintcustomerID;

privateDateTimeorderDate;

privateDateTimeshippedDate;

privateDataSetorderDetails;

//Publicproperties,toexposethebusinessentity'sstate

publicintOrderID

{

get{returnorderID;}

set

{

BeforeChange(this,newEntityEventArgs());//Raisea'before'event

orderID=value;

AfterChange(this,newEntityEventArgs());//Raisean'after'event

}

}

publicintCustomerID

{

get{returncustomerID;}

set

{

BeforeChange(this,newEntityEventArgs());//Raisea'before'event

customerID=value;

AfterChange(this,newEntityEventArgs());//Raisean'after'event

}

}

publicDateTimeOrderDate

{

get{returnorderDate;}

set

{

BeforeChange(this,newEntityEventArgs());//Raisea'before'event

orderDate=value;

AfterChange(this,newEntityEventArgs());//Raisean'after'event

}

}

publicDateTimeShippedDate

{

get{returnshippedDate;}

set

{

BeforeChange(this,newEntityEventArgs());//Raisea'before'event

shippedDate=value;

AfterChange(this,newEntityEventArgs());//Raisean'after'event

}

}

//Additionalmembers,asrequired...

}

XmlSerializerclass

...

//CreateanXmlSerializerobject,toserializeOrderEntity-typeobjects

XmlSerializerserializer=newXmlSerializer(typeof(OrderEntity));

//SerializeanOrderEntityobjecttoanXMLfilenamed

"MyXmlOrderEntity.xml"

TextWriterwriter=newStreamWriter("MyXmlOrderEntity.xml");

serializer.Serialize(writer,order);

writer.Close();

{

[WebService(Namespace="urn:MyWebServiceNamespace")]

publicclassOrderWS:System.Web.Services.WebService

{

[WebMethod]

publicOrderEntityGetOrder(intorderID)

{

//CreateanOrderDALCobject.

OrderDALCdalcOrder=newOrderDALC();

//UsedalcOrdertogetanOrderEntityobjectforthespecifiedorder

ID.

//ThiscodeassumestheOrderDALCclasshasamethodnamedGetOrder,

//whichtakesanOrderIDasaparameterandreturnsanOrderEntity

object

//containingallthedataforthisorder.

OrderEntityorder=dalcOrder.GetOrder(10248);

//ReturntheOrderEntityobject.Theobjectwillbeserialized

automatically.

returnorder;

}

[WebMethod]

publicvoidUpdateOrder(OrderEntityorder)

{

//CreateanOrderDALCobject.

OrderDALCdalcOrder=newOrderDALC();

//UsedalcOrdertosavetheOrderEntityobject'sdatatothedatabase.

//ThiscodeassumestheOrderDALCclasshasamethodnamedUpdateOrder,

//whichreceivesanOrderEntityobjectandsavesthedatatothe

database.

dalcOrder.UpdateOrder(order);

}

<OrderEntityxmlns:xsd="http://www.w3.org/2001/XMLSchema"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

<OrderID>10248</OrderID>

<CustomerID>VINET</CustomerID>

<OrderDate>1996-07-04T00:00:00.0000000+01:00</OrderDate>

<OrderDetails>...seebelow...</OrderDetails>

<ShippedDate>1996-07-16T00:00:00.0000000+01:00</ShippedDate>

</OrderEntity>

<xs:schemaid="NewDataSet"xmlns=""

xmlns:xs="http://www.w3.org/2001/XMLSchema"

xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">

<xs:elementname="NewDataSet"msdata:IsDataSet="true"msdata:Locale="en-

UK">

<xs:complexType>

<xs:choicemaxOccurs="unbounded">

<xs:elementname="OrderDetails">

<xs:complexType>

<xs:sequence>

<xs:elementname="OrderID"type="xs:int"minOccurs="0"/>

<xs:elementname="ProductID"type="xs:int"minOccurs="0"/>

<xs:elementname="UnitPrice"type="xs:decimal"minOccurs="0"

/>

<xs:elementname="Quantity"type="xs:short"minOccurs="0"/>

</xs:sequence>

</xs:complexType>

</xs:element>

</xs:choice>

</xs:complexType>

</xs:element>

</xs:schema>

<diffgr:diffgramxmlns:msdata="urn:schemas-microsoft-com:xml-msdata"

xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1">

<NewDataSet>

<OrderDetailsdiffgr:id="OrderDetails1"msdata:rowOrder="0"

diffgr:hasChanges="inserted">

<OrderID>10248</OrderID>

<ProductID>11</ProductID>

<UnitPrice>14</UnitPrice>

<Quantity>12</Quantity>

</OrderDetails>

<OrderDetailsdiffgr:id="OrderDetails2"msdata:rowOrder="1"

diffgr:hasChanges="inserted">

<OrderID>10248</OrderID>

<ProductID>42</ProductID>

<UnitPrice>9.8</UnitPrice>

<Quantity>10</Quantity>

</OrderDetails>

<OrderDetailsdiffgr:id="OrderDetails3"msdata:rowOrder="2"

diffgr:hasChanges="inserted">

<OrderID>10248</OrderID>

<ProductID>72</ProductID>

<UnitPrice>34.8</UnitPrice>

<Quantity>5</Quantity>

</OrderDetails>

</NewDataSet>

</diffgr:diffgram>

</OrderDetails>

publicclassOrderEntity

{

[XmlAttribute(AttributeName="ID")]

publicintOrderID{...getandsetcode,asbefore...}

[XmlAttribute(AttributeName="CustID")]

publicstringCustomerID{...getandsetcode,asbefore...}

[XmlElement(ElementName="Ordered")]

publicDateTimeOrderDate{...getandsetcode,asbefore...}

publicDataSetOrderDetails{...getandsetcode,asbefore...}

[XmlElement(ElementName="Shipped")

publicDateTimeShippedDate{...getandsetcode,asbefore...}

//Additionalmembers,asrequired...

}

<OrderID="10248"

CustID="VINET"

xmlns="urn:MyNamespace"

xmlns:xsd="http://www.w3.org/2001/XMLSchema"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

<Ordered>1996-07-04T00:00:00.0000000+01:00</Ordered>

<OrderDetails>...detailssameasbefore...</OrderDetails>

<Shipped>1996-07-16T00:00:00.0000000+01:00</Shipped>

</Order>

SoapFormatterclass

...

//CreateaSoapFormatterobject,toserializeOrderEntity-typeobjects

SoapFormatterformatter=newSoapFormatter();

//SerializeanOrderEntityobjecttoaSOAP(XML)filenamed

"MySoapOrderEntity.xml"

FileStreamstream=File.Create("MySoapOrderEntity.xml");

formatter.Serialize(stream,order);

stream.Close();

publicclassOrderEntity

{

//Members,asbefore

relatedtypes

...

[Serializable]

publicclassOrderEntity:ISerializable

{

//Serializationfunction,calledbytheSoapFormatterduringserialization

voidISerializable.GetObjectData(SerializationInfoinfo,StreamingContext

ctxt)

{

//AddeachfieldtotheSerializationInfoobject

info.AddValue("OrderID",orderID);

//Additionalcode,asrequired...

}

//Deserializationconstructor,calledbytheSoapFormatterduring

deserialization

publicOrderEntity(SerializationInfoinfo,StreamingContextctxt)

{

//DeserializefromtheSerializationInfoobjecttotheOrderEntity

fields

orderID=(int)info.GetValue("OrderID",typeof(int));

//Additionalcode,asrequired...

}

//Othermembers,asbefore...

}

BinaryFormatterclass

...

//CreateaBinaryFormatterobject,toserializeOrderEntity-typeobjects

BinaryFormatterformatter=newBinaryFormatter();

//SerializeanOrderEntityobjecttoabinaryfilenamed

"MyBinaryOrderEntity.dat"

FileStreamstream=File.Create("MyBinaryOrderEntity.dat");

formatter.Serialize(stream,order);

stream.Close();