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This article introduces the relevant knowledge of "server-side WCF data instance analysis". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

PublicclassMySyncProvider:KnowledgeSyncProvider,IChangeDataRetriever,INotifyingChangeApplierTarget

{

/ / Thenameofthemetadatastorecustomcolumnthatisusedtosaveatimestampoflastchangeonan

/ / iteminthemetadatastoresowecandochangedetection.

ConststringTIMESTAMP_COLUMNNAME= "timestamp"

/ / Thisisoursampleinmemorydatastorewhichforsimplicty,storessetsofstringname-ProcessChangeBatchpairs

/ / referencedbyidentifiersofthetype'Guid'

MySimpleDataStore_store

/ / UsetheSyncFramework'soptionalmetadatastoretotrackversioninformation

SqlMetadataStore_metadataStore=null;// represents a metadata store implemented by using a lightweight database to store metadata.

ReplicaMetadata_metadata=null;// provides access to replica metadata and item metadata in the metadata store. ReplicaMetadata also provides services for deletion detection and helpers for implementing synchronization provider methods

Privatestring_name=null

Privatestring_folderPath=null

Privatestring_replicaMetadataFile=null

Privatestring_replicaIdFile=null

/ / Theprovider'suniqueidentifier

SyncId_replicaId=null

SyncIdFormatGroup_idFormats=null

SyncSessionContext_currentSessionContext=null

/ / Constructadatastorebyprovidinganamefortheendpoint (replica) and

/ / afiletowhichwe'llpersistthesyncmetadata (file)

PublicMySyncProvider (stringfolderPath,stringname)

{

Namename=name

FolderPathfolderPath=folderPath

ReplicaMetadataFile=_folderPath.ToString () + "+ _ name.ToString () +" .metadata "

ReplicaIdFile=_folderPath.ToString () + "+ _ name.ToString () +" .Replicaid "

SetItemIdFormatandReplicaIdFormatforusingGuidids.

IdFormats=newSyncIdFormatGroup ()

IdFormats.ItemIdFormat.IsVariableLength=false

IdFormats.ItemIdFormat.Length=16

IdFormats.ReplicaIdFormat.IsVariableLength=false

IdFormats.ReplicaIdFormat.Length=16

}

PublicSyncIdReplicaId

{

Get

{

If (_ replicaId==null)

{

ReplicaId=GetReplicaIdFromFile (_ replicaIdFile)

}

Return_replicaId

}

}

# regionMetadataStoreRelatedMethods

PrivatevoidInitializeMetadataStore ()

{

Valuesforaddingacustomfieldtothemetadatastore

Listfields=newList ()

SyncIdid=ReplicaId

Createoropenthemetadatastore,initializingitwiththeidformatswe'llusetoreferenceouritemsandendpoints

If (! File.Exists (_ replicaMetadataFile))

{

Fields.Add (newFieldSchema (TIMESTAMP_COLUMNNAME,typeof (System.UInt64)

/ / create a metadata store file with the specified name and location, and then return the metadata store object that represents the file.

_ metadataStore=SqlMetadataStore.CreateStore (_ replicaMetadataFile)

/ / create and initialize the copy of the metadata in the metadata store and return a copy metadata object that is used to access the copy metadata.

_ metadata=_metadataStore.InitializeReplicaMetadata (ID format schema of the _ idFormats,// provider

ReplicaId,// the copy ID associated with this metadata

Fields,// a collection of schema information for custom metadata fields for each metadata item. If there is no custom metadata field, it can be referenced for null

Null/*Noindexestocreate*/); / / A list of index schemas that can be used to find items in the metadata store more efficiently. If there is no custom index, it can be a null reference

}

Else

{

_ metadataStore=SqlMetadataStore.OpenStore (_ replicaMetadataFile); / / Open an existing metadata store file and return the metadata store object that represents the file

_ metadata=_metadataStore.GetReplicaMetadata (_ idFormats,_replicaId); / / gets the replica metadata object used to access the replica metadata in the metadata store.

}

}

PrivatevoidCloseMetadataStore ()

{

MetadataStore.Dispose ()

MetadataStore=null

}

/ / Updatethemetadatastorewithchangesthathaveoccuredonthedatastoresincethelasttimeitwasupdated.

PublicvoidUpdateMetadataStoreWithLocalChanges ()

{

SyncVersionnewVersion=newSyncVersion (0gramme metadata.GetNextTickCount ())

Metadata.DeleteDetector.MarkAllItemsUnreported ()

Foreach (Guididin_store.Ids)

{

ItemDatadata=_store.Get (id)

ItemMetadataitem=null

/ / Lookupanitem'smetadatabyitsID

Item=_metadata.FindItemMetadataById (newSyncId (id))

If (null==item)

{

Newitem,musthavebeencreatedsincethatlasttimethemetadatawasupdated.

Createtheitemmetadatarequiredforsync (givingitaSyncIDandaversion,definedtobeaDWORDandaULONGLONG

Forcreates,simplyprovidetherelativereplicaID (0) andthetickcountfortheprovider (everincreasing)

Item=_metadata.CreateItemMetadata (newSyncId (id), newVersion)

Item.ChangeVersion=newVersion

SaveItemMetadata (item,data.TimeStamp)

}

Else

{

If (data.TimeStamp > item.GetUInt64Field (TIMESTAMP_COLUMNNAME)) / / theitemhaschangedsincethelastsyncoperation.

{

/ / ChangedItem,thisitemhaschangedsincethelasttimethemetadatawasupdated.

/ / Assignanewversionbysimplystating "who" modifiedthisitem (0=local/me) and "when" (tickcountforthestore)

Item.ChangeVersion=newVersion

SaveItemMetadata (item,data.TimeStamp)

}

Else

{

/ / Unchangeditem,nothinghaschangessojustmarkitaslivesothatthemetadataknowsithasnotbeendeleted.

_ metadata.DeleteDetector.ReportLiveItemById (newSyncId (id))

}

}

}

Nowgobackthroughtheitemsthatarenolongerinthestoreandmarkthemasdeletedinthemetadata.

Thissetstheitemasatombstone.

Foreach (ItemMetadataitemin_metadata.DeleteDetector.FindUnreportedItems ())

{

Item.MarkAsDeleted (newVersion)

SaveItemMetadata (item,0); / / settimestampto0fortombstones

}

}

PrivatevoidSaveItemMetadata (ItemMetadataitem,ulongtimeStamp)

{

Item.SetCustomField (TIMESTAMP_COLUMNNAME,timeStamp)

SaveItemMetadata (item)

}

PrivatevoidSaveItemMetadata (ItemMetadataitem)

{

Metadata.SaveItemMetadata (item)

}

/ / MethodforcleaninguptombstonesolderthanacertainTimeSpan

PublicvoidCleanupTombstones (TimeSpantimespan)

{

InitializeMetadataStore ()

MetadataStore.BeginTransaction (); / / start an explicit transaction on the metadata store

Metadata.CleanupDeletedItems (timespan)

MetadataStore.CommitTransaction (); / / commit explicit transactions that have been initiated against the metadata store

CloseMetadataStore ()

}

# endregionMetadataStoreRelatedMethods

# regionKnowledgeSyncProviderOverrides

/ / BeginSessioniscalledatthebeginningofeachsyncoperation. Doinitializationhere. Forexampleupdate

/ / metadataifitwasnotupdatedastheactualdatawaschanged.

PublicoverridevoidBeginSession (SyncProviderPositionposition,SyncSessionContextsyncSessionContext)

{

BeginSession ()

CurrentSessionContext=syncSessionContext

}

/ / EndSessioniscalledafterthesyncoperationiscompleted. Cleanuphappenshere.

PublicoverridevoidEndSession (SyncSessionContextsyncSessionContext)

{

EndSession ()

}

/ / Simplyaskthemetadatastoretocomputemychangebatchforme,providingthebatchsizeandtheknowledgeoftheotherendpoint!

/ / Theengineisaskingforthelistofchangesthatthedestinationproviderdoesnotknowabout.

/ / SyncKnowledge: represents the knowledge that the copy has about its own item store.

/ / all public static (shared in VisualBasic) members of this type are thread safe. The thread safety of any instance member is not guaranteed.

PublicoverrideChangeBatchGetChangeBatch (uintbatchSize,SyncKnowledgedestinationKnowledge,outobjectchangeDataRetriever)

{

ChangeBatchbatch=_metadata.GetChangeBatch (batchSize,destinationKnowledge)

ChangeDataRetriever=this;//thisiswherethetransfermechanism/protocolwouldgo.Foraninmemoryprovider,thisissufficient

Returnbatch

}

/ / ThisisonlycalledwhentheenginehasdetectedthatthedestinationisoutofdateduetoTombstonecleanup.

PublicoverrideFullEnumerationChangeBatchGetFullEnumerationChangeBatch (uintbatchSize,SyncIdlowerEnumerationBound,SyncKnowledgeknowledgeForDataRetrieval,outobjectchangeDataRetriever)

{

FullEnumerationChangeBatchbatch=_metadata.GetFullEnumerationChangeBatch (batchSize,lowerEnumerationBound,knowledgeForDataRetrieval)

ChangeDataRetriever=this;//thisiswherethetransfermechanism/protocolwouldgo.Foraninmemoryprovider,thisissufficient

Returnbatch

}

/ / specify a batchSize of 10 and the corresponding knowledge

PublicoverridevoidGetSyncBatchParameters (outuintbatchSize,outSyncKnowledgeknowledge)

{

BatchSize=10

Knowledge=_metadata.GetKnowledge ()

}

/ / apply modification

PublicoverridevoidProcessChangeBatch (ConflictResolutionPolicyresolutionPolicy,ChangeBatchsourceChanges

ObjectchangeDataRetriever,SyncCallbackssyncCallback,SyncSessionStatisticssessionStatistics)

{

MetadataStore.BeginTransaction ()

Get all local modifications from the original data store

IEnumerablelocalChanges=_metadata.GetLocalVersions (sourceChanges)

Createachangeapplierobjecttomakechangeapplicationeasier (maketheenginecallme

WhenitneedsdataandwhenIshouldsavedata)

NotifyingChangeApplierchangeApplier=newNotifyingChangeApplier (_ idFormats)

ChangeApplier.ApplyChanges (resolutionPolicy,sourceChanges,changeDataRetrieverasIChangeDataRetriever,localChanges,_metadata.GetKnowledge ()

_ metadata.GetForgottenKnowledge (), this,_currentSessionContext,syncCallback)

MetadataStore.CommitTransaction ()

}

/ / Iffullenumerationisneededbecause thisproviderisoutofdateduetotombstonecleanup,thenthismethodwillbecalledbytheengine.

PublicoverridevoidProcessFullEnumerationChangeBatch (ConflictResolutionPolicyresolutionPolicy,FullEnumerationChangeBatchsourceChanges,objectchangeDataRetriever,SyncCallbackssyncCallback,SyncSessionStatisticssessionStatistics)

{

MetadataStore.BeginTransaction ()

Getallmylocalchangeversionsfromthemetadatastore

IEnumerablelocalChanges=_metadata.GetFullEnumerationLocalVersions (sourceChanges)

Createachangeapplierobjecttomakechangeapplicationeasier (maketheenginecallme

WhenitneedsdataandwhenIshouldsavedata)

NotifyingChangeApplierchangeApplier=newNotifyingChangeApplier (_ idFormats)

ChangeApplier.ApplyFullEnumerationChanges (resolutionPolicy,sourceChanges,changeDataRetrieverasIChangeDataRetriever,localChanges,_metadata.GetKnowledge ()

_ metadata.GetForgottenKnowledge (), this,_currentSessionContext,syncCallback)

MetadataStore.CommitTransaction ()

}

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