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<h1><a name="kanchor4"></a>Bidirectional Replication</h1>
<p>It's quite often the case that you need replication in both directions. For example when you have a mobile device which keeps the data in sync with a desktop PC. Changes on the both partners have to be replicated to the other partner.</p>
<p>First, make sure that you've prepared and configured db4o properly. <a href="simple_example.htm" target="" title="" alt="" class="MCXref" xrefformat="See "{paratext}"">See "Simple Example"</a></p>
<p>Start a replication-session with the two replication partners. Note that no replication direction is set.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IObjectContainer desktopDatabase = OpenDatabase(DesktopDatabaseName);
IObjectContainer mobileDatabase = OpenDatabase(MobileDatabaseName);
IReplicationProvider dektopReplicationProvider
= new Db4oEmbeddedReplicationProvider(desktopDatabase);
IReplicationProvider mobileReplicationProvider
= new Db4oEmbeddedReplicationProvider(mobileDatabase);
IReplicationSession replicationSession
= Replication.Begin(dektopReplicationProvider, mobileReplicationProvider);</pre>
<div class="codesnippet-meta">Db4oReplicationExamples.cs: Prepare bidirectional replication
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim desktopDatabase As IObjectContainer = OpenDatabase(DesktopDatabaseName)
Dim mobileDatabase As IObjectContainer = OpenDatabase(MobileDatabaseName)
Dim dektopReplicationProvider As IReplicationProvider _
= New Db4oEmbeddedReplicationProvider(desktopDatabase)
Dim mobileReplicationProvider As IReplicationProvider _
= New Db4oEmbeddedReplicationProvider(mobileDatabase)
Dim replicationSession As IReplicationSession _
= Replication.Begin(dektopReplicationProvider, mobileReplicationProvider)</pre>
<div class="codesnippet-meta">Db4oReplicationExamples.vb: Prepare bidirectional replication
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<p>Then get the changed objects from both replication partners. Each replication partner returns the updated and created object in a object-set. Then iterate over both object-sets and replicate the changes. </p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">// First get the changes of the two replication-partners
IObjectSet changesOnDesktop = replicationSession.ProviderA().ObjectsChangedSinceLastReplication();
IObjectSet changesOnMobile = replicationSession.ProviderB().ObjectsChangedSinceLastReplication();
// then iterate over both change-sets and replicate it
foreach (object changedObjectOnDesktop in changesOnDesktop)
{
replicationSession.Replicate(changedObjectOnDesktop);
}
foreach (object changedObjectOnMobile in changesOnMobile)
{
replicationSession.Replicate(changedObjectOnMobile);
}
replicationSession.Commit();</pre>
<div class="codesnippet-meta">Db4oReplicationExamples.cs: Bidirectional replication
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">' First get the changes of the two replication-partners
Dim changesOnDesktop As IObjectSet _
= replicationSession.ProviderA().ObjectsChangedSinceLastReplication()
Dim changesOnMobile As IObjectSet _
= replicationSession.ProviderB().ObjectsChangedSinceLastReplication()
' then iterate over both change-sets and replicate it
For Each changedObjectOnDesktop As Object In changesOnDesktop
replicationSession.Replicate(changedObjectOnDesktop)
Next
For Each changedObjectOnMobile As Object In changesOnMobile
replicationSession.Replicate(changedObjectOnMobile)
Next
replicationSession.Commit()</pre>
<div class="codesnippet-meta">Db4oReplicationExamples.vb: Bidirectional replication
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