ConnectionString 在第二次执行时丢失

Question

我正在使用 asp.net core 2.0 和 dapper。我有一个包装 IDbConnection 接口并且只公开某些方法的类。这是该类的简短版本。

public class MyConnectionString : IMyConnectionString
{
    private readonly IDbConnection _connection;

    public int ConnectionTimeout => _connection.ConnectionTimeout;
    public string Database => _connection.Database;
    public string ConnectionString { get => null; set => _connection.ConnectionString = value; }
    public ConnectionState State => _connection.State;

    public MyConnectionString(IOptions<ConnectionProviderOptions> connProvOpts, EncryptionHelper encHelper)
    {
        var con = "some logic to get the connection string.";
        _connection = new SqlConnection(con);
    }

    public int Execute(string query, object parameters = null)
    {
        using (var con = _connection) { return con.Execute(query, parameters); }
    }
}

我通过构造函数将这个类注入到我的存储库服务中。例如，这是一个可以调用它的方法：

internal class SomeRepository
{
    private readonly IMyConnectionString _connection;

    public SomeRepository(IMyConnectionString connection)
    {
        _connection = connection;
    }

    public void ExecuteSomeQuery(Object params)
    {
        var query = "Some query...";
        _connection.Execute(query, params);
    }
}

现在的问题是，如果我在一个请求（2 个不同的服务）中调用 _connection.Execute(query, params); 两次，第二次调用 ConnectionString 类中的 ConnectionString 值是空的。我已经尝试在 Transient 和 Request 范围内绑定它，看看它是否会保留它，但没有运气。知道为什么会发生这种情况，或者我如何保存它，这样我就不必在每次请求时都创建连接字符串？

Answer 1

将Connection 包裹在using 中会在执行结束时处理Connection：就像@Jasen 在cmets 中所说的那样。

在您的情况下，我会获取连接并在构造函数中创建的Connection 上执行：完全删除using。

你不应该创建SqlConnection，因为你正在实现依赖注入。你应该：

• 实施IDisposable 以在收集您的课程时释放您的连接。
• 通过SqlConnection 工厂来创建您的SqlConnection，将您的创建逻辑与您的类分开。

你的类应该是这样的：

public class MyConnectionString : IMyConnectionString
{
    private readonly IDbConnection _connection;

    public int ConnectionTimeout => _connection.ConnectionTimeout;
    public string Database => _connection.Database;
    public string ConnectionString 
    {     
        get => null; 
        set => _connection.ConnectionString = value; 
    }

    public ConnectionState State => _connection.State;

    public MyConnectionString(IOptions<ConnectionProviderOptions> connProvOpts, EncryptionHelper encHelper)
    {
        string con = "some logic to get the connection string.";
        _connection = new SqlConnection(con);
    }

    public int Execute(string query, object parameters = null)
    {
        return _connection.Execute(query, parameters);
    }
}

使用IDisposable 实现：

using System;
public class MyConnectionString : IMyConnectionString, IDisposable
{
    private readonly IDbConnection _connection;

    public int ConnectionTimeout => _connection.ConnectionTimeout;
    public string Database => _connection.Database;
    public string ConnectionString 
    {     
        get => null; 
        set => _connection.ConnectionString = value; 
    }

    public ConnectionState State => _connection.State;

    public MyConnectionString(IOptions<ConnectionProviderOptions> connProvOpts, EncryptionHelper encHelper)
    {
        string con = "some logic to get the connection string.";
        _connection = new SqlConnection(con);
    }

    public int Execute(string query, object parameters = null)
    {
        return _connection.Execute(query, parameters);
    }

    public void Dispose()
    {
        _connection.Dispose();
    }
}

用你自己的ISqlConnectionFactory工厂：

public class MyConnectionString : IMyConnectionString, IDisposable
{
    private readonly IDbConnection _connection;
    private readonly ISqlConnectionFactory _factory;

    public int ConnectionTimeout => _connection.ConnectionTimeout;
    public string Database => _connection.Database;
    public string ConnectionString 
    {     
        get => null; 
        set => _connection.ConnectionString = value; 
    }

    public ConnectionState State => _connection.State;

    public MyConnectionString(IOptions<ConnectionProviderOptions> connProvOpts, EncryptionHelper encHelper, ISqlConnectionFactory factory)
    {
        _factory = factory;
        _connection = _factory.CreateConnection(connProvOpts, encHelper);
    }

    public int Execute(string query, object parameters = null)
    {
        return _connection.Execute(query, parameters);
    }
}

public interface ISqlConnectionFactory
{
    SqlConnection CreateConnection(IOptions<ConnectionProviderOptions> connProvOpts, EncryptionHelper encHelper);
}

public class SqlConnectionFactory : ISqlConnectionFactory
{
    public SqlConnectionFactory()
    {
         // Maybe initialization?
    }

    public SqlConnection CreateConnection(IOptions<ConnectionProviderOptions> connProvOpts, EncryptionHelper encHelper)
    {
        string con = "some logic to get the connection string.";
        _connection = new SqlConnection(con);
    }
}

就个人而言，我会在每次调用 Execute 时创建并处置 Connection。这意味着在Execute 之外，您的连接将关闭并释放资源。