Как установить двунаправленный обмен добавочными изменениями данных между клиентом и сервером

В этом разделе описан обмен изменениями данных с помощью двунаправленной синхронизации между базой данных сервера и клиентской базой данных SQL Server Compact. В примерах, приведенных в этом разделе, обсуждаются следующие типы и события служб Sync Framework:

• DbServerSyncProvider

• SyncAdapter

• SqlCeClientSyncProvider

• SyncDirection

• SyncSession

• SyncStatistics

• SyncTable

• SyncAgent

• CreatingSchema и CreatingSchemaEventArgs

• SchemaCreated и SchemaCreatedEventArgs

Сведения о способах запуска образца кода см. в подразделе «Образцы приложений в разделах инструкций» раздела Программирование распространенных задач синхронизации клиента и сервера.

Пример

Пример кода в этом разделе демонстрирует настройку двунаправленной синхронизации для таблицы Customer из образца базы данных Sync Framework. Общие сведения о свойствах, которые используются для указания направления синхронизации, см. в разделе Как задать синхронизацию моментальными снимками, с загрузкой, с передачей и двунаправленную.

Двунаправленная синхронизация требует, чтобы добавочные изменения данных отслеживались и применялись в базах данных сервера и клиента. Службы Sync Framework выполняют обработку в клиентской базе данных. Тем не менее, базу данных сервера необходимо настроить и задать команды для выборки изменений и применения их к базе данных сервера. Эти команды включены в пример кода. Сведения о настройке базы данных сервера см. в разделе Отслеживание изменений в базе данных сервера.

Ключевые элементы API-интерфейса

В этом разделе приведены примеры кода, которые определяют ключевые элементы API-интерфейса, используемые в двунаправленной синхронизации. В следующем примере кода указывается направление синхронизации и способ создания таблицы на клиенте.

SyncTable customerSyncTable = new SyncTable("Customer");
customerSyncTable.CreationOption = TableCreationOption.DropExistingOrCreateNewTable;
customerSyncTable.SyncDirection = SyncDirection.Bidirectional;
customerSyncTable.SyncGroup = customerSyncGroup;
this.Configuration.SyncTables.Add(customerSyncTable);

Dim customerSyncTable As New SyncTable("Customer")
customerSyncTable.CreationOption = TableCreationOption.DropExistingOrCreateNewTable
customerSyncTable.SyncDirection = SyncDirection.Bidirectional
customerSyncTable.SyncGroup = customerSyncGroup
Me.Configuration.SyncTables.Add(customerSyncTable)

В следующем примере кода указана команда для получения от сервера нового значения привязки. В данном случае значение timestamp после получения сохраняется в клиентской базе данных. При каждой синхронизации используются вновь полученное значение привязки и последнее значение привязки от предыдущей синхронизации: синхронизируется набор изменений между этими верхней и нижней границами. Параметры привязки используются в командах выборки изменений из базы данных сервера.

SqlCommand selectNewAnchorCommand = new SqlCommand();
string newAnchorVariable = "@" + SyncSession.SyncNewReceivedAnchor;
selectNewAnchorCommand.CommandText = 
    "SELECT " + newAnchorVariable + " = min_active_rowversion() - 1";
selectNewAnchorCommand.Parameters.Add(newAnchorVariable, SqlDbType.Timestamp);
selectNewAnchorCommand.Parameters[newAnchorVariable].Direction = ParameterDirection.Output;
selectNewAnchorCommand.Connection = serverConn;
this.SelectNewAnchorCommand = selectNewAnchorCommand;

Dim selectNewAnchorCommand As New SqlCommand()
Dim newAnchorVariable As String = "@" + SyncSession.SyncNewReceivedAnchor
With selectNewAnchorCommand
    .CommandText = "SELECT " + newAnchorVariable + " = min_active_rowversion() - 1"
    .Parameters.Add(newAnchorVariable, SqlDbType.Timestamp)
    .Parameters(newAnchorVariable).Direction = ParameterDirection.Output
    .Connection = serverConn
End With
Me.SelectNewAnchorCommand = selectNewAnchorCommand

Следующий пример кода определяет команду выборки на сервере добавочных обновлений, которые применяются к клиенту. Это инструкция SELECT, в которую входят столбцы синхронизации. В предложении WHERE указываются столбцы отслеживания и значения привязки, которые получает SelectNewAnchorCommand. Предложение WHERE включает также UpdateId <> @sync_client_id. Этот параметр предотвращает немедленную передачу изменений с сервера обратно на клиент во время одного сеанса синхронизации. Если приложению необходима такая передача изменений, эту инструкцию следует пропустить. Сведения о методах фильтрации загруженных данных см. в разделе Как фильтровать строки и столбцы.

SqlCommand customerIncrUpdates = new SqlCommand();
customerIncrUpdates.CommandText =
    "SELECT CustomerId, CustomerName, SalesPerson, CustomerType " +
    "FROM Sales.Customer " +
    "WHERE (UpdateTimestamp > @sync_last_received_anchor " +
    "AND UpdateTimestamp <= @sync_new_received_anchor " +
    "AND UpdateId <> @sync_client_id " +
    "AND NOT (InsertTimestamp > @sync_last_received_anchor " +
    "AND InsertId <> @sync_client_id))";
customerIncrUpdates.Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp);
customerIncrUpdates.Parameters.Add("@" + SyncSession.SyncNewReceivedAnchor, SqlDbType.Timestamp);
customerIncrUpdates.Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier);
customerIncrUpdates.Connection = serverConn;
customerSyncAdapter.SelectIncrementalUpdatesCommand = customerIncrUpdates;

Dim customerIncrUpdates As New SqlCommand()
With customerIncrUpdates
    .CommandText = _
        "SELECT CustomerId, CustomerName, SalesPerson, CustomerType " _
      & "FROM Sales.Customer " _
      & "WHERE (UpdateTimestamp > @sync_last_received_anchor " _
      & "AND UpdateTimestamp <= @sync_new_received_anchor " _
      & "AND UpdateId <> @sync_client_id " _
      & "AND NOT (InsertTimestamp > @sync_last_received_anchor " _
      & "AND InsertId <> @sync_client_id))"
    .Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp)
    .Parameters.Add("@" + SyncSession.SyncNewReceivedAnchor, SqlDbType.Timestamp)
    .Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier)
    .Connection = serverConn
End With
customerSyncAdapter.SelectIncrementalUpdatesCommand = customerIncrUpdates

В следующем примере кода приведена команда для применения добавочных обновлений от клиента к серверу. Это инструкция UPDATE, включающая столбцы для обновления. Она включает предложение WHERE, которое снова использует значения привязки и идентификатор клиента. Предложение WHERE включает также @sync_force_write = 1. Этот параметр обеспечивает принудительное применение конфликтующих обновлений. Дополнительные сведения о @sync_force_write и других переменных сеанса см. в разделе Как использовать переменные сеанса.

SqlCommand customerUpdates = new SqlCommand();
customerUpdates.CommandText =
    "UPDATE Sales.Customer SET " + 
    "CustomerName = @CustomerName, SalesPerson = @SalesPerson, " + 
    "CustomerType = @CustomerType, " + 
    "UpdateId = @sync_client_id " +           
    "WHERE (CustomerId = @CustomerId) " + 
    "AND (@sync_force_write = 1 " + 
    "OR (UpdateTimestamp <= @sync_last_received_anchor " +
    "OR UpdateId = @sync_client_id)) " + 
    "SET @sync_row_count = @@rowcount";
customerUpdates.Parameters.Add("@CustomerName", SqlDbType.NVarChar);
customerUpdates.Parameters.Add("@SalesPerson", SqlDbType.NVarChar);
customerUpdates.Parameters.Add("@CustomerType", SqlDbType.NVarChar);
customerUpdates.Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier);
customerUpdates.Parameters.Add("@CustomerId", SqlDbType.UniqueIdentifier);
customerUpdates.Parameters.Add("@" + SyncSession.SyncForceWrite, SqlDbType.Bit);
customerUpdates.Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp);
customerUpdates.Parameters.Add("@" + SyncSession.SyncRowCount, SqlDbType.Int);
customerUpdates.Connection = serverConn;
customerSyncAdapter.UpdateCommand = customerUpdates;

Dim customerUpdates As New SqlCommand()
With customerUpdates
    .CommandText = _
        "UPDATE Sales.Customer SET " _
      & "CustomerName = @CustomerName, SalesPerson = @SalesPerson, " _
      & "CustomerType = @CustomerType, " _
      & "UpdateId = @sync_client_id " _
      & "WHERE (CustomerId = @CustomerId) " _
      & "AND (@sync_force_write = 1 " _
      & "OR (UpdateTimestamp <= @sync_last_received_anchor " _
      & "OR UpdateId = @sync_client_id)) " _
      & "SET @sync_row_count = @@rowcount"
    .Parameters.Add("@CustomerName", SqlDbType.NVarChar)
    .Parameters.Add("@SalesPerson", SqlDbType.NVarChar)
    .Parameters.Add("@CustomerType", SqlDbType.NVarChar)
    .Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier)
    .Parameters.Add("@CustomerId", SqlDbType.UniqueIdentifier)
    .Parameters.Add("@" + SyncSession.SyncForceWrite, SqlDbType.Bit)
    .Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp)
    .Parameters.Add("@" + SyncSession.SyncRowCount, SqlDbType.Int)
    .Connection = serverConn
End With
customerSyncAdapter.UpdateCommand = customerUpdates

Полный пример кода

Приведенный ниже полный пример кода содержит все ранее описанные примеры и дополнительный код синхронизации. Он также иллюстрирует применение SyncStatistics для отображения сведений о сеансе синхронизации и использование событий CreatingSchema и SchemaCreated для ввода значения по умолчанию в столбец CustomerId. Для работы примеру необходим класс Utility, сведения о котором можно найти в разделе Инструкции по классу Utility для поставщика базы данных.

using System;
using System.IO;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlServerCe;
using Microsoft.Synchronization;
using Microsoft.Synchronization.Data;
using Microsoft.Synchronization.Data.Server;
using Microsoft.Synchronization.Data.SqlServerCe;

namespace Microsoft.Samples.Synchronization
{
    class Program
    {
        static void Main(string[] args)
        {

            //The SampleStats class handles information from the SyncStatistics
            //object that the Synchronize method returns.
            SampleStats sampleStats = new SampleStats();

            //Request a password for the client database, and delete
            //and re-create the database. The client synchronization
            //provider also enables you to create the client database 
            //if it does not exist.
            Utility.SetPassword_SqlCeClientSync();
            Utility.DeleteAndRecreateCompactDatabase(Utility.ConnStr_SqlCeClientSync, true);
            
            //Initial synchronization. Instantiate the SyncAgent
            //and call Synchronize.
            SampleSyncAgent sampleSyncAgent = new SampleSyncAgent();
            SyncStatistics syncStatistics = sampleSyncAgent.Synchronize();
            sampleStats.DisplayStats(syncStatistics, "initial");

            //Make changes on the server and client.
            Utility.MakeDataChangesOnServer("Customer");
            Utility.MakeDataChangesOnClient("Customer");

            //Subsequent synchronization.
            syncStatistics = sampleSyncAgent.Synchronize();
            sampleStats.DisplayStats(syncStatistics, "subsequent");

            //Return server data back to its original state.
            Utility.CleanUpServer();

            //Exit.
            Console.Write("\nPress Enter to close the window.");
            Console.ReadLine();
        }
    }

    //Create a class that is derived from 
    //Microsoft.Synchronization.SyncAgent.
    public class SampleSyncAgent : SyncAgent
    {
        public SampleSyncAgent()
        {            
            //Instantiate a client synchronization provider and specify it
            //as the local provider for this synchronization agent.
            this.LocalProvider = new SampleClientSyncProvider();

            //Instantiate a server synchronization provider and specify it
            //as the remote provider for this synchronization agent.
            this.RemoteProvider = new SampleServerSyncProvider();

            //Create a Customer SyncGroup. This is not required
            //for the single table we are synchronizing; it is typically
            //used so that changes to multiple related tables are 
            //synchronized at the same time.
            SyncGroup customerSyncGroup = new SyncGroup("Customer");

            //Add the Customer table: specify a synchronization direction of
            //Bidirectional, and that an existing table should be dropped.
            SyncTable customerSyncTable = new SyncTable("Customer");
            customerSyncTable.CreationOption = TableCreationOption.DropExistingOrCreateNewTable;
            customerSyncTable.SyncDirection = SyncDirection.Bidirectional;
            customerSyncTable.SyncGroup = customerSyncGroup;
            this.Configuration.SyncTables.Add(customerSyncTable);
        }
    }

    //Create a class that is derived from 
    //Microsoft.Synchronization.Server.DbServerSyncProvider.
    public class SampleServerSyncProvider : DbServerSyncProvider
    {
        public SampleServerSyncProvider()
        {
            //Create a connection to the sample server database.
            Utility util = new Utility();
            SqlConnection serverConn = new SqlConnection(Utility.ConnStr_DbServerSync);
            this.Connection = serverConn;
          
            //Create a command to retrieve a new anchor value from
            //the server. In this case, we use a timestamp value
            //that is retrieved and stored in the client database.
            //During each synchronization, the new anchor value and
            //the last anchor value from the previous synchronization
            //are used: the set of changes between these upper and
            //lower bounds is synchronized.
            //
            //SyncSession.SyncNewReceivedAnchor is a string constant; 
            //you could also use @sync_new_received_anchor directly in 
            //your queries.
            SqlCommand selectNewAnchorCommand = new SqlCommand();
            string newAnchorVariable = "@" + SyncSession.SyncNewReceivedAnchor;
            selectNewAnchorCommand.CommandText = 
                "SELECT " + newAnchorVariable + " = min_active_rowversion() - 1";
            selectNewAnchorCommand.Parameters.Add(newAnchorVariable, SqlDbType.Timestamp);
            selectNewAnchorCommand.Parameters[newAnchorVariable].Direction = ParameterDirection.Output;
            selectNewAnchorCommand.Connection = serverConn;
            this.SelectNewAnchorCommand = selectNewAnchorCommand;
            
            //Create a SyncAdapter for the Customer table, and then define
            //the commands to synchronize changes:
            //* SelectIncrementalInsertsCommand, SelectIncrementalUpdatesCommand,
            //  and SelectIncrementalDeletesCommand are used to select changes
            //  from the server that the client provider then applies to the client.
            //* InsertCommand, UpdateCommand, and DeleteCommand are used to apply
            //  to the server the changes that the client provider has selected
            //  from the client.

            //Create the SyncAdapter.
            SyncAdapter customerSyncAdapter = new SyncAdapter("Customer");            
            
            //Select inserts from the server.
            SqlCommand customerIncrInserts = new SqlCommand();
            customerIncrInserts.CommandText =  
                "SELECT CustomerId, CustomerName, SalesPerson, CustomerType " +
                "FROM Sales.Customer " +
                "WHERE (InsertTimestamp > @sync_last_received_anchor " +
                "AND InsertTimestamp <= @sync_new_received_anchor " +
                "AND InsertId <> @sync_client_id)";
            customerIncrInserts.Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp);
            customerIncrInserts.Parameters.Add("@" + SyncSession.SyncNewReceivedAnchor, SqlDbType.Timestamp);
            customerIncrInserts.Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier);
            customerIncrInserts.Connection = serverConn;
            customerSyncAdapter.SelectIncrementalInsertsCommand = customerIncrInserts;

            //Apply inserts to the server.
            SqlCommand customerInserts = new SqlCommand();
            customerInserts.CommandText =
                "INSERT INTO Sales.Customer (CustomerId, CustomerName, SalesPerson, CustomerType, InsertId, UpdateId) " +
                "VALUES (@CustomerId, @CustomerName, @SalesPerson, @CustomerType, @sync_client_id, @sync_client_id) " +
                "SET @sync_row_count = @@rowcount";
            customerInserts.Parameters.Add("@CustomerId", SqlDbType.UniqueIdentifier);
            customerInserts.Parameters.Add("@CustomerName", SqlDbType.NVarChar);
            customerInserts.Parameters.Add("@SalesPerson", SqlDbType.NVarChar);
            customerInserts.Parameters.Add("@CustomerType", SqlDbType.NVarChar);
            customerInserts.Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier);
            customerInserts.Parameters.Add("@" + SyncSession.SyncRowCount, SqlDbType.Int);
            customerInserts.Connection = serverConn;
            customerSyncAdapter.InsertCommand = customerInserts;
                                    
            
            //Select updates from the server.
            SqlCommand customerIncrUpdates = new SqlCommand();
            customerIncrUpdates.CommandText =
                "SELECT CustomerId, CustomerName, SalesPerson, CustomerType " +
                "FROM Sales.Customer " +
                "WHERE (UpdateTimestamp > @sync_last_received_anchor " +
                "AND UpdateTimestamp <= @sync_new_received_anchor " +
                "AND UpdateId <> @sync_client_id " +
                "AND NOT (InsertTimestamp > @sync_last_received_anchor " +
                "AND InsertId <> @sync_client_id))";
            customerIncrUpdates.Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp);
            customerIncrUpdates.Parameters.Add("@" + SyncSession.SyncNewReceivedAnchor, SqlDbType.Timestamp);
            customerIncrUpdates.Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier);
            customerIncrUpdates.Connection = serverConn;
            customerSyncAdapter.SelectIncrementalUpdatesCommand = customerIncrUpdates;
            
            //Apply updates to the server.
            SqlCommand customerUpdates = new SqlCommand();
            customerUpdates.CommandText =
                "UPDATE Sales.Customer SET " + 
                "CustomerName = @CustomerName, SalesPerson = @SalesPerson, " + 
                "CustomerType = @CustomerType, " + 
                "UpdateId = @sync_client_id " +           
                "WHERE (CustomerId = @CustomerId) " + 
                "AND (@sync_force_write = 1 " + 
                "OR (UpdateTimestamp <= @sync_last_received_anchor " +
                "OR UpdateId = @sync_client_id)) " + 
                "SET @sync_row_count = @@rowcount";
            customerUpdates.Parameters.Add("@CustomerName", SqlDbType.NVarChar);
            customerUpdates.Parameters.Add("@SalesPerson", SqlDbType.NVarChar);
            customerUpdates.Parameters.Add("@CustomerType", SqlDbType.NVarChar);
            customerUpdates.Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier);
            customerUpdates.Parameters.Add("@CustomerId", SqlDbType.UniqueIdentifier);
            customerUpdates.Parameters.Add("@" + SyncSession.SyncForceWrite, SqlDbType.Bit);
            customerUpdates.Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp);
            customerUpdates.Parameters.Add("@" + SyncSession.SyncRowCount, SqlDbType.Int);
            customerUpdates.Connection = serverConn;
            customerSyncAdapter.UpdateCommand = customerUpdates;


            //Select deletes from the server.
            SqlCommand customerIncrDeletes = new SqlCommand();
            customerIncrDeletes.CommandText =
                "SELECT CustomerId, CustomerName, SalesPerson, CustomerType " +
                "FROM Sales.Customer_Tombstone " +
                "WHERE (@sync_initialized = 1 " +
                "AND DeleteTimestamp > @sync_last_received_anchor " +
                "AND DeleteTimestamp <= @sync_new_received_anchor " +
                "AND DeleteId <> @sync_client_id)";
            customerIncrDeletes.Parameters.Add("@" + SyncSession.SyncInitialized, SqlDbType.Bit);
            customerIncrDeletes.Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp);
            customerIncrDeletes.Parameters.Add("@" + SyncSession.SyncNewReceivedAnchor, SqlDbType.Timestamp);
            customerIncrDeletes.Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier);
            customerIncrDeletes.Connection = serverConn;
            customerSyncAdapter.SelectIncrementalDeletesCommand = customerIncrDeletes;

            //Apply deletes to the server.            
            SqlCommand customerDeletes = new SqlCommand();
            customerDeletes.CommandText =
                "DELETE FROM Sales.Customer " +
                "WHERE (CustomerId = @CustomerId) " + 
                "AND (@sync_force_write = 1 " + 
                "OR (UpdateTimestamp <= @sync_last_received_anchor " + 
                "OR UpdateId = @sync_client_id)) " + 
                "SET @sync_row_count = @@rowcount " + 
                "IF (@sync_row_count > 0)  BEGIN " + 
                "UPDATE Sales.Customer_Tombstone " + 
                "SET DeleteId = @sync_client_id " +
                "WHERE (CustomerId = @CustomerId) " + 
                "END";
            customerDeletes.Parameters.Add("@CustomerId", SqlDbType.UniqueIdentifier);       
            customerDeletes.Parameters.Add("@" + SyncSession.SyncForceWrite, SqlDbType.Bit);
            customerDeletes.Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp);
            customerDeletes.Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier);
            customerDeletes.Parameters.Add("@" + SyncSession.SyncRowCount, SqlDbType.Int);           
            customerDeletes.Connection = serverConn;
            customerSyncAdapter.DeleteCommand = customerDeletes;     


            //Add the SyncAdapter to the server synchronization provider.
            this.SyncAdapters.Add(customerSyncAdapter);

        }
    }

    //Create a class that is derived from 
    //Microsoft.Synchronization.Data.SqlServerCe.SqlCeClientSyncProvider.
    //You can just instantiate the provider directly and associate it
    //with the SyncAgent, but here we use this class to handle client 
    //provider events.
    public class SampleClientSyncProvider : SqlCeClientSyncProvider
    {
            
        public SampleClientSyncProvider()
        {
            //Specify a connection string for the sample client database.
            Utility util = new Utility();
            this.ConnectionString = Utility.ConnStr_SqlCeClientSync;

            //We use the CreatingSchema event to change the schema
            //by using the API. We use the SchemaCreated event to 
            //change the schema by using SQL.
            this.CreatingSchema +=new EventHandler<CreatingSchemaEventArgs>(SampleClientSyncProvider_CreatingSchema);
            this.SchemaCreated +=new EventHandler<SchemaCreatedEventArgs>(SampleClientSyncProvider_SchemaCreated);
        }

        private void SampleClientSyncProvider_CreatingSchema(object sender, CreatingSchemaEventArgs e)
        {
            //Set the RowGuid property because it is not copied
            //to the client by default. This is also a good time
            //to specify literal defaults with .Columns[ColName].DefaultValue;
            //but we will specify defaults like NEWID() by calling
            //ALTER TABLE after the table is created.
            Console.Write("Creating schema for " + e.Table.TableName + " | ");                        
            e.Schema.Tables["Customer"].Columns["CustomerId"].RowGuid = true;
        }

        private void SampleClientSyncProvider_SchemaCreated(object sender, SchemaCreatedEventArgs e)
        {        
            //Call ALTER TABLE on the client. This must be done
            //over the same connection and within the same
            //transaction that Sync Framework uses
            //to create the schema on the client.
            Utility util = new Utility();
            Utility.MakeSchemaChangesOnClient(e.Connection, e.Transaction, e.Table.TableName);
            Console.WriteLine("Schema created for " + e.Table.TableName);
        }
    }

    //Handle the statistics that are returned by the SyncAgent.
    public class SampleStats
    {
        public void DisplayStats(SyncStatistics syncStatistics, string syncType)
        {
            Console.WriteLine(String.Empty);
            if (syncType == "initial")
            {
                Console.WriteLine("****** Initial Synchronization ******");
            }
            else if (syncType == "subsequent")
            {
                Console.WriteLine("***** Subsequent Synchronization ****");
            }

            Console.WriteLine("Start Time: " + syncStatistics.SyncStartTime);
            Console.WriteLine("Total Changes Uploaded: " + syncStatistics.TotalChangesUploaded);
            Console.WriteLine("Total Changes Downloaded: " + syncStatistics.TotalChangesDownloaded);
            Console.WriteLine("Complete Time: " + syncStatistics.SyncCompleteTime);
            Console.WriteLine(String.Empty);
        }
    }
}

Imports System
Imports System.IO
Imports System.Text
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.SqlServerCe
Imports Microsoft.Synchronization
Imports Microsoft.Synchronization.Data
Imports Microsoft.Synchronization.Data.Server
Imports Microsoft.Synchronization.Data.SqlServerCe

Class Program

    Shared Sub Main(ByVal args() As String)

        'The SampleStats class handles information from the SyncStatistics
        'object that the Synchronize method returns.
        Dim sampleStats As New SampleStats()

        'Request a password for the client database, and delete
        'and re-create the database. The client synchronization
        'provider also enables you to create the client database 
        'if it does not exist.
        Utility.SetPassword_SqlCeClientSync()
        Utility.DeleteAndRecreateCompactDatabase(Utility.ConnStr_SqlCeClientSync, True)

        'Initial synchronization. Instantiate the SyncAgent
        'and call Synchronize.
        Dim sampleSyncAgent As New SampleSyncAgent()
        Dim syncStatistics As SyncStatistics = sampleSyncAgent.Synchronize()
        sampleStats.DisplayStats(syncStatistics, "initial")

        'Make changes on the server and client.
        Utility.MakeDataChangesOnServer("Customer")
        Utility.MakeDataChangesOnClient("Customer")

        'Subsequent synchronization.
        syncStatistics = sampleSyncAgent.Synchronize()
        sampleStats.DisplayStats(syncStatistics, "subsequent")

        'Return server data back to its original state.
        Utility.CleanUpServer()

        'Exit.
        Console.Write(vbLf + "Press Enter to close the window.")
        Console.ReadLine()

    End Sub 'Main
End Class 'Program

'Create a class that is derived from 
'Microsoft.Synchronization.SyncAgent.
Public Class SampleSyncAgent
    Inherits SyncAgent

    Public Sub New()
        'Instantiate a client synchronization provider and specify it
        'as the local provider for this synchronization agent.
        Me.LocalProvider = New SampleClientSyncProvider()

        'Instantiate a server synchronization provider and specify it
        'as the remote provider for this synchronization agent.
        Me.RemoteProvider = New SampleServerSyncProvider()

        'Create a Customer SyncGroup. This is not required
        'for the single table we are synchronizing; it is typically
        'used so that changes to multiple related tables are 
        'synchronized at the same time.
        Dim customerSyncGroup As New SyncGroup("Customer")

        'Add the Customer table: specify a synchronization direction of
        'Bidirectional, and that an existing table should be dropped.
        Dim customerSyncTable As New SyncTable("Customer")
        customerSyncTable.CreationOption = TableCreationOption.DropExistingOrCreateNewTable
        customerSyncTable.SyncDirection = SyncDirection.Bidirectional
        customerSyncTable.SyncGroup = customerSyncGroup
        Me.Configuration.SyncTables.Add(customerSyncTable)

    End Sub 'New
End Class 'SampleSyncAgent

'Create a class that is derived from 
'Microsoft.Synchronization.Server.DbServerSyncProvider.
Public Class SampleServerSyncProvider
    Inherits DbServerSyncProvider

    Public Sub New()
        'Create a connection to the sample server database.
        Dim util As New Utility()
        Dim serverConn As New SqlConnection(Utility.ConnStr_DbServerSync)
        Me.Connection = serverConn

        'Create a command to retrieve a new anchor value from
        'the server. In this case, we use a timestamp value
        'that is retrieved and stored in the client database.
        'During each synchronization, the new anchor value and
        'the last anchor value from the previous synchronization
        'are used: the set of changes between these upper and
        'lower bounds is synchronized.
        '
        'SyncSession.SyncNewReceivedAnchor is a string constant; 
        'you could also use @sync_new_received_anchor directly in 
        'your queries.
        Dim selectNewAnchorCommand As New SqlCommand()
        Dim newAnchorVariable As String = "@" + SyncSession.SyncNewReceivedAnchor
        With selectNewAnchorCommand
            .CommandText = "SELECT " + newAnchorVariable + " = min_active_rowversion() - 1"
            .Parameters.Add(newAnchorVariable, SqlDbType.Timestamp)
            .Parameters(newAnchorVariable).Direction = ParameterDirection.Output
            .Connection = serverConn
        End With
        Me.SelectNewAnchorCommand = selectNewAnchorCommand

        'Create a SyncAdapter for the Customer table, and then define
        'the commands to synchronize changes:
        '* SelectIncrementalInsertsCommand, SelectIncrementalUpdatesCommand,
        '  and SelectIncrementalDeletesCommand are used to select changes
        '  from the server that the client provider then applies to the client.
        '* InsertCommand, UpdateCommand, and DeleteCommand are used to apply
        '  to the server the changes that the client provider has selected
        '  from the client.

        'Create the SyncAdapter.
        Dim customerSyncAdapter As New SyncAdapter("Customer")

        'Select inserts from the server.
        Dim customerIncrInserts As New SqlCommand()
        With customerIncrInserts
            .CommandText = _
                "SELECT CustomerId, CustomerName, SalesPerson, CustomerType " _
              & "FROM Sales.Customer " _
              & "WHERE (InsertTimestamp > @sync_last_received_anchor " _
              & "AND InsertTimestamp <= @sync_new_received_anchor " _
              & "AND InsertId <> @sync_client_id)"
            .Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp)
            .Parameters.Add("@" + SyncSession.SyncNewReceivedAnchor, SqlDbType.Timestamp)
            .Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier)
            .Connection = serverConn
        End With
        customerSyncAdapter.SelectIncrementalInsertsCommand = customerIncrInserts

        'Apply inserts to the server.
        Dim customerInserts As New SqlCommand()
        With customerInserts
            .CommandText = _
                "INSERT INTO Sales.Customer (CustomerId, CustomerName, SalesPerson, CustomerType, InsertId, UpdateId) " _
              & "VALUES (@CustomerId, @CustomerName, @SalesPerson, @CustomerType, @sync_client_id, @sync_client_id) " _
              & "SET @sync_row_count = @@rowcount"
            .Parameters.Add("@CustomerId", SqlDbType.UniqueIdentifier)
            .Parameters.Add("@CustomerName", SqlDbType.NVarChar)
            .Parameters.Add("@SalesPerson", SqlDbType.NVarChar)
            .Parameters.Add("@CustomerType", SqlDbType.NVarChar)
            .Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier)
            .Parameters.Add("@" + SyncSession.SyncRowCount, SqlDbType.Int)
            .Connection = serverConn
        End With
        customerSyncAdapter.InsertCommand = customerInserts


        'Select updates from the server.
        Dim customerIncrUpdates As New SqlCommand()
        With customerIncrUpdates
            .CommandText = _
                "SELECT CustomerId, CustomerName, SalesPerson, CustomerType " _
              & "FROM Sales.Customer " _
              & "WHERE (UpdateTimestamp > @sync_last_received_anchor " _
              & "AND UpdateTimestamp <= @sync_new_received_anchor " _
              & "AND UpdateId <> @sync_client_id " _
              & "AND NOT (InsertTimestamp > @sync_last_received_anchor " _
              & "AND InsertId <> @sync_client_id))"
            .Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp)
            .Parameters.Add("@" + SyncSession.SyncNewReceivedAnchor, SqlDbType.Timestamp)
            .Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier)
            .Connection = serverConn
        End With
        customerSyncAdapter.SelectIncrementalUpdatesCommand = customerIncrUpdates

        'Apply updates to the server.
        Dim customerUpdates As New SqlCommand()
        With customerUpdates
            .CommandText = _
                "UPDATE Sales.Customer SET " _
              & "CustomerName = @CustomerName, SalesPerson = @SalesPerson, " _
              & "CustomerType = @CustomerType, " _
              & "UpdateId = @sync_client_id " _
              & "WHERE (CustomerId = @CustomerId) " _
              & "AND (@sync_force_write = 1 " _
              & "OR (UpdateTimestamp <= @sync_last_received_anchor " _
              & "OR UpdateId = @sync_client_id)) " _
              & "SET @sync_row_count = @@rowcount"
            .Parameters.Add("@CustomerName", SqlDbType.NVarChar)
            .Parameters.Add("@SalesPerson", SqlDbType.NVarChar)
            .Parameters.Add("@CustomerType", SqlDbType.NVarChar)
            .Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier)
            .Parameters.Add("@CustomerId", SqlDbType.UniqueIdentifier)
            .Parameters.Add("@" + SyncSession.SyncForceWrite, SqlDbType.Bit)
            .Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp)
            .Parameters.Add("@" + SyncSession.SyncRowCount, SqlDbType.Int)
            .Connection = serverConn
        End With
        customerSyncAdapter.UpdateCommand = customerUpdates

        'Select deletes from the server.
        Dim customerIncrDeletes As New SqlCommand()
        With customerIncrDeletes
            .CommandText = _
                "SELECT CustomerId, CustomerName, SalesPerson, CustomerType " _
              & "FROM Sales.Customer_Tombstone " _
              & "WHERE (@sync_initialized = 1 " _
              & "AND DeleteTimestamp > @sync_last_received_anchor " _
              & "AND DeleteTimestamp <= @sync_new_received_anchor " _
              & "AND DeleteId <> @sync_client_id)"
            .Parameters.Add("@" + SyncSession.SyncInitialized, SqlDbType.Bit)
            .Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp)
            .Parameters.Add("@" + SyncSession.SyncNewReceivedAnchor, SqlDbType.Timestamp)
            .Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier)
            .Connection = serverConn
        End With
        customerSyncAdapter.SelectIncrementalDeletesCommand = customerIncrDeletes

        'Apply deletes to the server.            
        Dim customerDeletes As New SqlCommand()
        With customerDeletes
            .CommandText = _
                "DELETE FROM Sales.Customer " _
              & "WHERE (CustomerId = @CustomerId) " _
              & "AND (@sync_force_write = 1 " _
              & "OR (UpdateTimestamp <= @sync_last_received_anchor " _
              & "OR UpdateId = @sync_client_id)) " _
              & "SET @sync_row_count = @@rowcount " _
              & "IF (@sync_row_count > 0)  BEGIN " _
              & "UPDATE Sales.Customer_Tombstone " _
              & "SET DeleteId = @sync_client_id " _
              & "WHERE (CustomerId = @CustomerId) " _
              & "END"
            .Parameters.Add("@CustomerId", SqlDbType.UniqueIdentifier)
            .Parameters.Add("@" + SyncSession.SyncForceWrite, SqlDbType.Bit)
            .Parameters.Add("@" + SyncSession.SyncLastReceivedAnchor, SqlDbType.Timestamp)
            .Parameters.Add("@" + SyncSession.SyncClientId, SqlDbType.UniqueIdentifier)
            .Parameters.Add("@" + SyncSession.SyncRowCount, SqlDbType.Int)
            .Connection = serverConn
        End With
        customerSyncAdapter.DeleteCommand = customerDeletes


        'Add the SyncAdapter to the server synchronization provider.
        Me.SyncAdapters.Add(customerSyncAdapter)

    End Sub 'New 
End Class 'SampleServerSyncProvider

'Create a class that is derived from 
'Microsoft.Synchronization.Data.SqlServerCe.SqlCeClientSyncProvider.
'You can just instantiate the provider directly and associate it
'with the SyncAgent, but here we use this class to handle client 
'provider events.
Public Class SampleClientSyncProvider
    Inherits SqlCeClientSyncProvider


    Public Sub New()
        'Specify a connection string for the sample client database.
        Dim util As New Utility()
        Me.ConnectionString = Utility.ConnStr_SqlCeClientSync

        'We use the CreatingSchema event to change the schema
        'by using the API. We use the SchemaCreated event to 
        'change the schema by using SQL.
        AddHandler Me.CreatingSchema, AddressOf SampleClientSyncProvider_CreatingSchema
        AddHandler Me.SchemaCreated, AddressOf SampleClientSyncProvider_SchemaCreated

    End Sub 'New


    Private Sub SampleClientSyncProvider_CreatingSchema(ByVal sender As Object, ByVal e As CreatingSchemaEventArgs)
        'Set the RowGuid property because it is not copied
        'to the client by default. This is also a good time
        'to specify literal defaults with .Columns[ColName].DefaultValue;
        'but we will specify defaults like NEWID() by calling
        'ALTER TABLE after the table is created.
        Console.Write("Creating schema for " + e.Table.TableName + " | ")
        e.Schema.Tables("Customer").Columns("CustomerId").RowGuid = True

    End Sub 'SampleClientSyncProvider_CreatingSchema


    Private Sub SampleClientSyncProvider_SchemaCreated(ByVal sender As Object, ByVal e As SchemaCreatedEventArgs)
        'Call ALTER TABLE on the client. This must be done
        'over the same connection and within the same
        'transaction that Sync Framework uses
        'to create the schema on the client.
        Dim util As New Utility()
        Utility.MakeSchemaChangesOnClient(e.Connection, e.Transaction, e.Table.TableName)
        Console.WriteLine("Schema created for " + e.Table.TableName)

    End Sub 'SampleClientSyncProvider_SchemaCreated
End Class 'SampleClientSyncProvider

'Handle the statistics that are returned by the SyncAgent.
Public Class SampleStats

    Public Sub DisplayStats(ByVal syncStatistics As SyncStatistics, ByVal syncType As String)
        Console.WriteLine(String.Empty)
        If syncType = "initial" Then
            Console.WriteLine("****** Initial Synchronization ******")
        ElseIf syncType = "subsequent" Then
            Console.WriteLine("***** Subsequent Synchronization ****")
        End If

        Console.WriteLine("Start Time: " & syncStatistics.SyncStartTime)
        Console.WriteLine("Total Changes Uploaded: " & syncStatistics.TotalChangesUploaded)
        Console.WriteLine("Total Changes Downloaded: " & syncStatistics.TotalChangesDownloaded)
        Console.WriteLine("Complete Time: " & syncStatistics.SyncCompleteTime)
        Console.WriteLine(String.Empty)

    End Sub 'DisplayStats
End Class 'SampleStats

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