让我先说明我现在意识到我是多么愚蠢。我已经开发了1年（到今天），这是我写的第一件事。我现在已经回到它，我不能做它的正面或反面。它曾经在一个非常简单的应用程序上工作，但那是在不久之前。
具体来说，LocalDBConn使用out会遇到问题，但就我而言，我记不清为什么。
指导，指针，重构，打击头部都是欢迎和赞赏！
public class MergeRepl
{
// Declare nessesary variables
private string subscriberName;
private string publisherName;
private string publicationName;
private string subscriptionDbName;
private string publicationDbName;
private MergePullSubscription mergeSubscription;
private MergePublication mergePublication;
private ServerConnection subscriberConn;
private ServerConnection publisherConn;
private Server theLocalSQLServer;
private ReplicationDatabase localRepDB;
public MergeRepl(string subscriber, string publisher, string publication, string subscriptionDB, string publicationDB)
{
subscriberName = subscriber;
publisherName = publisher;
publicationName = publication;
subscriptionDbName = subscriptionDB;
publicationDbName = publicationDB;
//Create connections to the Publisher and Subscriber.
subscriberConn = new ServerConnection(subscriberName);
publisherConn = new ServerConnection(publisherName);
// Define the pull mergeSubscription
mergeSubscription = new MergePullSubscription
{
ConnectionContext = subscriberConn,
DatabaseName = subscriptionDbName,
PublisherName = publisherName,
PublicationDBName = publicationDbName,
PublicationName = publicationName
};
// Ensure that the publication exists and that it supports pull subscriptions.
mergePublication = new MergePublication
{
Name = publicationName,
DatabaseName = publicationDbName,
ConnectionContext = publisherConn
};
// Create the local SQL Server instance
theLocalSQLServer = new Server(subscriberConn);
// Create a Replication DB Object to initiate Replication settings on local DB
localRepDB = new ReplicationDatabase(subscriptionDbName, subscriberConn);
// Check that the database exists locally
CreateDatabase(subscriptionDbName);
}
public void RunDataSync()
{
// Keep program from appearing 'Not Responding'
///// Application.DoEvents();
// Does the needed Databases exist on local SQLExpress Install
/////CreateDatabase("ContactDB");
try
{
// Connect to the Subscriber
subscriberConn.Connect();
// if the Subscription exists, then start the sync
if (mergeSubscription.LoadProperties())
{
// Check that we have enough metadata to start the agent
if (mergeSubscription.PublisherSecurity != null || mergeSubscription.DistributorSecurity != null)
{
// Synchronously start the merge Agent for the mergeSubscription
// lblStatus.Text = "Data Sync Started - Please Be Patient!";
mergeSubscription.SynchronizationAgent.Synchronize();
}
else
{
throw new ApplicationException("There is insufficient metadata to synchronize the subscription." +
"Recreate the subscription with the agent job or supply the required agent properties at run time.");
}
}
else
{
// do something here if the pull mergeSubscription does not exist
// throw new ApplicationException(String.Format("A mergeSubscription to '{0}' does not exist on {1}", publicationName, subscriberName));
CreateMergeSubscription();
}
}
catch (Exception ex)
{
// Implement appropriaate error handling here
throw new ApplicationException("The subscription could not be synchronized. Verify that the subscription has been defined correctly.", ex);
//CreateMergeSubscription();
}
finally
{
subscriberConn.Disconnect();
}
}
public void CreateMergeSubscription()
{
// Keep program from appearing 'Not Responding'
// Application.DoEvents();
try
{
if (mergePublication.LoadProperties())
{
if ((mergePublication.Attributes & PublicationAttributes.AllowPull) == 0)
{
mergePublication.Attributes |= PublicationAttributes.AllowPull;
}
// Make sure that the agent job for the mergeSubscription is created.
mergeSubscription.CreateSyncAgentByDefault = true;
// Create the pull mergeSubscription at the Subscriber.
mergeSubscription.Create();
Boolean registered = false;
// Verify that the mergeSubscription is not already registered.
foreach (MergeSubscription existing in mergePublication.EnumSubscriptions())
{
if (existing.SubscriberName == subscriberName
&& existing.SubscriptionDBName == subscriptionDbName
&& existing.SubscriptionType == SubscriptionOption.Pull)
{
registered = true;
}
}
if (!registered)
{
// Register the local mergeSubscription with the Publisher.
mergePublication.MakePullSubscriptionWellKnown(
subscriberName, subscriptionDbName,
SubscriptionSyncType.Automatic,
MergeSubscriberType.Local, 0);
}
}
else
{
// Do something here if the publication does not exist.
throw new ApplicationException(String.Format(
"The publication '{0}' does not exist on {1}.",
publicationName, publisherName));
}
}
catch (Exception ex)
{
// Implement the appropriate error handling here.
throw new ApplicationException(String.Format("The subscription to {0} could not be created.", publicationName), ex);
}
finally
{
publisherConn.Disconnect();
}
}
/// <summary>
/// This will make sure the needed DataBase exists locally before allowing any interaction with it.
/// </summary>
/// <param name="whichDataBase">The name of the DataBase to check for.</param>
/// <returns>True if the specified DataBase exists, False if it doesn't.</returns>
public void CreateDatabase(string whichDataBase)
{
Database db;
LocalDBConn(whichDataBase, out theLocalSQLServer, out localRepDB, out db);
if (!theLocalSQLServer.Databases.Contains(whichDataBase))
{
//Application.DoEvents();
// Create the database on the instance of SQL Server.
db = new Database(theLocalSQLServer, whichDataBase);
db.Create();
}
localRepDB.Load();
localRepDB.EnabledMergePublishing = false;
localRepDB.CommitPropertyChanges();
if (!mergeSubscription.LoadProperties())
{
CreateMergeSubscription();
}
}
private void LocalDBConn(string databaseName, out Server server, out ReplicationDatabase replicationDatabase, out Database db)
{
db = server.Databases[replicationDatabase.Name];
}
/// <summary>
/// Checks for the existince of the Publication. If there is one it verify's Allow Pull is set
/// </summary>
/// <returns>True if Publication is present. False if not.</returns>
public bool CheckForPublication()
{
// If LoadProperties() returns TRUE then the Publication exists and is reachable
if (mergePublication.LoadProperties())
return true;
if ((mergePublication.Attributes & PublicationAttributes.AllowPull) == 0)
{
mergePublication.Attributes |= PublicationAttributes.AllowPull;
}
return false;
} // end CheckForPublication()
/// <summary>
/// Checks for the existence of a Subscription.
/// </summary>
/// <returns>True if a Subscription is present. False if not</returns>
public bool CheckForSubscription()
{
// Check for the existence of the Subscription
return mergeSubscription.IsExistingObject;
} // end CheckForSubscription()
}
Opps，我忘记了具体的错误。在server和replicationDatabase我收到“Out参数可能在访问”
private void LocalDBConn(string databaseName, out Server server, out ReplicationDatabase replicationDatabase, out Database db)
{
db = server.Databases[replicationDatabase.Name];
}
答案 0 :(得分：2)
private void LocalDBConn(string databaseName, out Server server, out ReplicationDatabase replicationDatabase, out Database db)
{
db = server.Databases[replicationDatabase.Name];
}
此方法不会构建，因为在方法返回之前未初始化out parameters。 out参数允许调用者将未实例化的对象传递给方法，然后该方法必须在返回之前通过所有路径初始化（不包括方法抛出异常）。基本上，out参数是方法声明“我将在返回之前实例化此对象”的语句。在LocalDBConn中，你没有这样做。
在C＃3.0语言规范中，详见5.1.6。
答案 1 :(得分：2)
看起来你可以安全地删除了。
我不确定如何编译，除非它可能是VS2003并且编译器没有检查这种类型的错误。
从MSDN：虽然作为out参数传递的变量在传递之前不必初始化，但是在方法返回之前需要调用方法来赋值。
private void LocalDBConn(string databaseName, Server server,
ReplicationDatabase replicationDatabase, out Database db)
{
db = server.Databases[replicationDatabase.Name];
}
或
private Database LocalDBConn(string databaseName, Server server,
ReplicationDatabase replicationDatabase)
{
return server.Databases[replicationDatabase.Name];
}
然后将CreateDatabase中的代码更新为：
Database db;
LocalDBConn(whichDataBase, theLocalSQLServer, localRepDB, out db);
或
Database db = LocalDBConn(whichDataBase, theLocalSQLServer, localRepDB);
答案 2 :(得分：1)
所有编译器都告诉您，Server和ReplicationDatabase是输出参数，但在从LocalDBConn方法返回之前，您没有为它们分配任何内容。
当使用out参数时，你应该对它们执行空检查，以确保它们已经在方法之外初始化，如果没有初始化它们。