Question

如果我创建了一个数据库，然后在2秒内尝试使用MS Sync Framework连接它，则会抛出异常“无法打开数据库......”

添加

Thread.Sleep(4000);

会导致代码正常工作，但我不希望设置困难，因为此代码将在平板电脑和其他弱硬件上运行，因此生成数据库的时间可能会大不相同。

我可以在创建后检查数据库是否存在，并且它总是立即执行，因此条件等待（旋转）不是一种选择。

using (SqlConnection masterConnection = new SqlConnection(masterConnectionString)) {
    using (SqlCommand sqlCommand = new SqlCommand(string.Format("IF NOT EXISTS (SELECT name FROM sys.databases WHERE name = '{0}') CREATE DATABASE {0}", databaseName), masterConnection)) {
        masterConnection.Open();
        sqlCommand.ExecuteNonQuery();
    }
}

bool databaseExist = false;
while (!databaseExist) {
    using (SqlConnection masterConnection = new SqlConnection(masterConnectionString)) {
        using (SqlCommand verifySqlCommand = new SqlCommand(string.Format("SELECT database_id FROM sys.databases WHERE name = '{0}'", databaseName), masterConnection)) {
            masterConnection.Open();
            databaseExist = (int)verifySqlCommand.ExecuteScalar() > 0; // Always true
        }
    }
    Thread.Sleep(1000);
}
...
using (SqlConnection sqlConnection = new SqlConnection(CONNECTION_STRING)) {
    SqlSyncScopeProvisioning sqlSyncScopeProvisioning = new SqlSyncScopeProvisioning(sqlConnection); // throw ("Cannot open database") db doesn't exist 
}

问题似乎与SqlConnection有关，第一个SqlConnection可以看到数据库存在，但第二个（新的）无法看到它存在于前几秒（在SqlConnection.Open（）上失败）。

堆栈跟踪

at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
at System.Data.SqlClient.SqlConnection.Open()
at Microsoft.Synchronization.Data.SyncUtil.TryOpenConnection(IDbConnection connection)
at Microsoft.Synchronization.Data.SyncUtil.OpenConnection(IDbConnection connection)
at Microsoft.Synchronization.Data.SqlServer.SqlEditionHelper.GetEdition(SqlConnection connection)
at Microsoft.Synchronization.Data.SqlServer.SqlSyncScopeProvisioning.set_Connection(SqlConnection value)
at Microsoft.Synchronization.Data.SqlServer.SqlSyncScopeProvisioning..ctor(SqlConnection connection, DbSyncScopeDescription scopeDescription, SqlSyncScopeProvisioningType provisioningType, Boolean expectConnection)
at Microsoft.Synchronization.Data.SqlServer.SqlSyncScopeProvisioning..ctor(SqlConnection connection)

Mark II基于@ CharlieBrown的回答

发布的@CharlieBrown代码本身可以正常工作，但不在我的设置中，以下代码演示了崩溃。如果取消注释手动抛出，则代码将正常工作，否则不会。

try {
    //If I manually throw this exception then code in catch will run fine, otherwise not.
    //throw new Exception("Cannot open database testDB"); 
    using (var sqlConnection = new SqlConnection(CONNECTION_STRING)) {
        SqlSyncScopeProvisioning sqlSyncScopeProvisioning = new SqlSyncScopeProvisioning(sqlConnection); // throw ("Cannot open database") db doesn't exist 
    }
} catch (Exception exception) {
    if (exception.Message.StartsWith("Cannot open database")) { // Database does not exist, try to create
        try {
            using (var masterConnection = new SqlConnection(masterConnectionString)) {
                using (var sqlCommand = new SqlCommand(string.Format("IF NOT EXISTS (SELECT name FROM sys.databases WHERE name = '{0}') CREATE DATABASE {0}", databaseName), masterConnection)) {
                    masterConnection.Open();
                    sqlCommand.ExecuteNonQuery();
                }
            }
            using (var sqlConnection = new SqlConnection(CONNECTION_STRING)) {
                SqlSyncScopeProvisioning sqlSyncScopeProvisioning = new SqlSyncScopeProvisioning(sqlConnection); // throw ("Cannot open database") db doesn't exist 
            }
        } catch (Exception ex) { // Always end up here
            // ex = System.Data.SqlClient.SqlException (0x80131904): Cannot open database "testDB" requested by the login. The login failed. Login failed for user ...
        }
    } else { // Other exception
        // Never hit
    }
}

编辑

每次使用建议更新代码，添加堆栈跟踪。添加了另一个代码示例来演示问题。

解决方案

在与@CharlieBrown交谈后，似乎没有解决这个问题的方法，因此我将通过运行SqlCommand来创建数据库（如果不存在），而不是尝试使用数据库然后在catch中创建（）如果例外。此代码仅在app start上运行。

Answer 1

在SQL Server有时间让数据库为同步做好准备之前，正在调用对SqlSyncScopeProvisioning的调用。我无法找到关于时间量的参考，但是在创建数据库之后，会发生几个触发器来准备数据库。

工作代码：针对LocalDb，Sql Server 2008r2，Sql Server 2012进行了测试

var connectionString = @"Data Source=(LocalDb)\v11.0;Initial Catalog=master;Integrated Security=True;";
var databaseName = "TestRepl";

using (var masterConnection = new SqlConnection(connectionString)) {
    using (var sqlCommand = new SqlCommand(string.Format("IF NOT EXISTS (SELECT name FROM sys.databases WHERE name = '{0}') CREATE DATABASE {0}", databaseName), masterConnection)) {
        masterConnection.Open();
        sqlCommand.ExecuteNonQuery();
    }
}

var syncConnectionString = string.Format(@"Data Source=(LocalDb)\v11.0;Initial Catalog={0};Integrated Security=True;", databaseName);
using(var sqlConnection = new SqlConnection(syncConnectionString)){
    SqlSyncScopeProvisioning sqlSyncScopeProvisioning = new SqlSyncScopeProvisioning(sqlConnection); // throw ("Cannot open database") db doesn't exist 
}

Answer 2

更新

再次阅读您的问题后，我注意到您使用了SqlSyncScopeProvisioning这是一个异步操作。您创建的数据库很可能最终完成配置 - 但由于它是 Asynchronous ，它在最终确定之前返回。所以下一个命令会触发，因为它尚未完成。

更可能没有分配的完成时间。

此外，您应该真正使用using command。它实现了IDisposable，它将帮助处理内存分配，这将有助于资源管理。

请注意以上述方式实现原始SQL，它可能会受到 SQL Injection 的影响。

您可能想要遵循Scott Chamberlain的建议，使用parameters。

private static void CreateSQLDatabase(string dbName)
{
     string createDb = "CREATE DATABASE @DatabaseName";
     using(SqlCommand buildSqlCommand = new SqlCommand(createDb, connectionForSql))
     {
          buildSqlCommand.Parameters.Add("@DatabaseName", dbName);
          connectionForSQL.Open();
          buildSqlCommand.ExecuteNonQuery();
     }
}

您还需要确保在创建之前数据库不存在，您可能还想在继续之前检查它是否确实成功创建和配置。

重要提示：“可能容易受到SQL注入”

using(SqlConnection connectionForSQL = new SqlConnection(@"Server=localhost; Integrated Security=SSPI; Database=master"))
{
     string verifyQuery = string.Format("SELECT database_id FROM sys.databases WHERE NAME = '{0}'", dbName);
     using(SqlCommand verifySqlCommand = new SqlCommand(verifyQuery, connectionForSQL))
     {
        connectionForSQL.Open();
        int databaseId = (int)verifySqlCommand.ExecuteScalar();
        return databaseId > 0;
     }
}

SqlCommand在C＃中创建数据库竞争条件

2 个答案:

更新