外文翻译 英文文献 使用两个dropdownlist过滤的主从报表大学毕设论文.docx

外文翻译 英文文献 使用两个dropdownlist过滤的主从报表大学毕设论文.docx

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外文翻译英文文献使用两个dropdownlist过滤的主从报表大学毕设论文

Master/DetailFilteringWithTwoDropDownLists

Introduction

Intheprevioustutorialweexaminedhowtodisplayasimplemaster/detailsreportusingasingleDropDownListpopulatedwiththecategoriesandaGridViewshowingthoseproductsthatbelongtotheselectedcategory.Thisreportpatternworkswellwhendisplayingrecordsthathaveaone-to-manyrelationshipandcaneasilybeextendedtoworkforscenariosthatincludemultipleone-to-manyrelationships.Forexample,anorderentrysystemwouldhavetablesthatcorrespondtocustomers,orders,andorderlineitems.Agivencustomermayhavemultipleorderswitheachorderconsistingofmultipleitems.SuchdatacanbepresentedtotheuserwithtwoDropDownListsandaGridView.ThefirstDropDownListwouldhavealistitemforeachcustomerinthedatabasewiththesecondone'scontentsbeingtheordersplacedbytheselectedcustomer.AGridViewwouldlistthelineitemsfromtheselectedorder.

WhiletheNorthwinddatabaseincludethecanonicalcustomer/order/orderdetailsinformationinitsCustomers,Orders,andOrderDetailstables,thesetablesaren'tcapturedinourarchitecture.Nonetheless,wecanstillillustrateusingtwodependentDropDownLists.ThefirstDropDownListwilllistthecategoriesandthesecondtheproductsbelongingtotheselectedcategory.ADetailsViewwillthenlistthedetailsoftheselectedproduct.

Step1:

CreatingandPopulatingtheCategoriesDropDownList

OurfirstgoalistoaddtheDropDownListthatliststhecategories.Thesestepswereexaminedindetailintheprecedingtutorial,butaresummarizedhereforcompleteness.

OpentheMasterDetailsDetails.aspxpageintheFilteringfolder,addaDropDownListtothepage,setitsIDpropertytoCategories,andthenclicktheConfigureDataSourcelinkinitssmarttag.FromtheDataSourceConfigurationWizardchoosetoaddanewdatasource.

Figure1:

AddaNewDataSourcefortheDropDownList（Clicktoviewfull-sizeimage）

Thenewdatasourceshould,naturally,beanObjectDataSource.NamethisnewObjectDataSourceCategoriesDataSourceandhaveitinvoketheCategoriesBLLobject'sGetCategories（）method.

Figure2:

ChoosetoUsetheCategoriesBLLClass（Clicktoviewfull-sizeimage）

Figure3:

ConfiguretheObjectDataSourcetoUsetheGetCategories（）Method（Clicktoviewfull-sizeimage）

AfterconfiguringtheObjectDataSourcewestillneedtospecifywhichdatasourcefieldshouldbedisplayedintheCategoriesDropDownListandwhichoneshouldbeconfiguredasthevalueforthelistitem.SettheCategoryNamefieldasthedisplayandCategoryIDasthevalueforeachlistitem.

Figure4:

HavetheDropDownListDisplaytheCategoryNameFieldandUseCategoryIDastheValue（Clicktoviewfull-sizeimage）

AtthispointwehaveaDropDownListcontrol（Categories）that'spopulatedwiththerecordsfromtheCategoriestable.WhentheuserchoosesanewcategoryfromtheDropDownListwe'llwantapostbacktooccurinordertorefreshtheproductDropDownListthatwe'regoingtocreateinStep2.Therefore,checktheEnableAutoPostBackoptionfromthecategoriesDropDownList'ssmarttag.

Figure5:

EnableAutoPostBackfortheCategoriesDropDownList（Clicktoviewfull-sizeimage）

Step2:

DisplayingtheSelectedCategory'sProductsinaSecondDropDownList

WiththeCategoriesDropDownListcompleted,ournextstepistodisplayaDropDownListofproductsbelongingtotheselectedcategory.Toaccomplishthis,addanotherDropDownListtothepagenamedProductsByCategory.AswiththeCategoriesDropDownList,createanewObjectDataSourcefortheProductsByCategoryDropDownListnamedProductsByCategoryDataSource.

Figure6:

AddaNewDataSourcefortheProductsByCategoryDropDownList（Clicktoviewfull-sizeimage）

Figure7:

CreateaNewObjectDataSourceNamedProductsByCategoryDataSource（Clicktoviewfull-sizeimage）

SincetheProductsByCategoryDropDownListneedstodisplayjustthoseproductsbelongingtotheselectedcategory,havetheObjectDataSourceinvoketheGetProductsByCategoryID（categoryID）methodfromtheProductsBLLobject.

Figure8:

ChoosetoUsetheProductsBLLClass（Clicktoviewfull-sizeimage）

Figure9:

ConfiguretheObjectDataSourcetoUsetheGetProductsByCategoryID（categoryID）Method（Clicktoviewfull-sizeimage）

InthefinalstepofthewizardweneedtospecifythevalueofthecategoryIDparameter.AssignthisparametertotheselecteditemfromtheCategoriesDropDownList.

Figure10:

PullthecategoryIDParameterValuefromtheCategoriesDropDownList（Clicktoviewfull-sizeimage）

WiththeObjectDataSourceconfigured,allthatremainsistospecifywhatdatasourcefieldsareusedforthedisplayandvalueoftheDropDownList'sitems.DisplaytheProductNamefieldandusetheProductIDfieldasthevalue.

Figure11:

SpecifytheDataSourceFieldsUsedfortheDropDownList'sListItems'TextandValueProperties（Clicktoviewfull-sizeimage）

WiththeObjectDataSourceandProductsByCategoryDropDownListconfiguredourpagewilldisplaytwoDropDownLists:

thefirstwilllistallofthecategorieswhilethesecondwilllistthoseproductsbelongingtotheselectedcategory.WhentheuserselectsanewcategoryfromthefirstDropDownList,apostbackwillensueandthesecondDropDownListwillberebound,showingthoseproductsthatbelongtothenewlyselectedcategory.Figures12and13showMasterDetailsDetails.aspxinactionwhenviewedthroughabrowser.

Figure12:

WhenFirstVisitingthePage,theBeveragesCategoryisSelected（Clicktoviewfull-sizeimage）

Figure13:

ChoosingaDifferentCategoryDisplaystheNewCategory'sProducts（Clicktoviewfull-sizeimage）

CurrentlytheproductsByCategoryDropDownList,whenchanged,doesnotcauseapostback.However,wewillwantapostbacktooccuronceweaddaDetailsViewtodisplaytheselectedproduct'sdetails（Step3）.Therefore,checktheEnableAutoPostBackcheckboxfromtheproductsByCategoryDropDownList'ssmarttag.

Figure14:

EnabletheAutoPostBackFeaturefortheproductsByCategoryDropDownList（Clicktoviewfull-sizeimage）

Step3:

UsingaDetailsViewtoDisplayDetailsfortheSelectedProduct

ThefinalstepistodisplaythedetailsfortheselectedproductinaDetailsView.Toaccomplishthis,addaDetailsViewtothepage,setitsIDpropertytoProductDetails,andcreateanewObjectDataSourceforit.ConfigurethisObjectDataSourcetopullitsdatafromtheProductsBLLclass'sGetProductByProductID（productID）methodusingtheselectedvalueoftheProductsByCategoryDropDownListforthevalueoftheproductIDparameter.

Figure15:

ChoosetoUsetheProductsBLLClass（Clicktoviewfull-sizeimage）

Figure16:

ConfiguretheObjectDataSourcetoUsetheGetProductByProductID（productID）Method（Clicktoviewfull-sizeimage）

Figure17:

PulltheproductIDParameterValuefromtheProductsByCategoryDropDownList（Clicktoviewfull-sizeimage）

YoucanchoosetodisplayanyoftheavailablefieldsintheDetailsView.I'veoptedtoremovetheProductID,SupplierID,andCategoryIDfieldsandreorderedandformattedtheremainingfields.Inaddition,IclearedouttheDetailsView'sHeightandWidthproperties,allowingtheDetailsViewtoexpandtothewidthneededtobestdisplayitsdataratherthanhavingitconstrainedtoaspecifiedsize.Thefullmarkupappearsbelow:

DetailsViewID="ProductDetails"runat="server"AutoGenerateRows="False"DataKeyNames="ProductID"DataSourceID="ObjectDataSource1"EnableViewState="False">

BoundFieldDataField="ProductName"HeaderText="Product"SortExpression="ProductName"/>

BoundFieldDataField="CategoryName"HeaderText="Category"ReadOnly="True"SortExpression="CategoryName"/>

BoundFieldDataField="SupplierName"HeaderText="Supplier"ReadOnly="True"SortExpression="SupplierName"/>

BoundFieldDataField="QuantityPerUnit"HeaderText="Qty/Unit"SortExpression="QuantityPerUnit"/>

BoundFieldDataField="UnitPrice"DataFormatString="{0:

c}"HeaderText="Price"HtmlEncode="False"SortExpression="UnitPrice"/>

BoundFieldDataField="UnitsInStock"HeaderText="UnitsInStock"SortExpression="UnitsInStock"/>

BoundFieldDataField="UnitsOnOrder"HeaderText="UnitsOnOrder"SortExpression="UnitsOnOrder"/>

BoundFieldDataField="ReorderLevel"HeaderText="ReorderLevel"SortExpression="ReorderLevel"/>

CheckBoxFieldDataField="Discontinued"HeaderText="Discontinued"SortExpression="Discontinued"/>

DetailsView>

TakeamomenttotryouttheMasterDetailsDetails.aspxpageinabrowser.Atfirstglanceitmayappearthateverythingisworkingasdesired,butthere'sasubtleproblem.WhenyouchooseanewcategorytheProductsByCategoryDropDownListisupdatedtoincludethoseproductsfortheselectedcategory,buttheProductDetailsDetailsViewcontinuedtoshowthepreviousproductinformation.TheDetailsViewisupdatedwhenchoosingadifferentproductfortheselectedcategory.Furthermore,ifyoutestthoroughlyenough,you'llfindthatifyoucontinuallychoosenewcategories（suchaschoosingBeveragesfromtheCategoriesDropDownList,thenCondiments,thenConfections）everyothercategoryselectioncausestheProductDetailsDetailsViewtoberefreshed.

Tohelpconcretizethisproblem,let'slookataspecificexample.WhenyoufirstvisitthepagetheBeveragescategoryisselectedandtherelatedproductsareloadedintheProductsByCategoryDropDownList.ChaiistheselectedproductanditsdetailsaredisplayedintheProductDetailsDetailsView,asshowninFigure18.

Figure18:

TheSelectedProduct'sDetailsareDisplayedinaDetailsView（Clicktoviewfull-sizeimage）

IfyouchangethecategoryselectionfromBeveragestoCondiments,apostbackoccursand