c#-4.0 - Autofac在运行时解析参数

Question

让我们直说吧。我有这样的接口(interface)和类:

public interface IDataBase
{
    DataTable GetSomeTableData();
}

我的类(class):

public class DataBase : IDataBase    
{
    private readonly string _connectionString;

    public DataBase(string connectionString)
    {
        this._connectionString = connectionString;
    }

    public DataTable GetSomeTableData()
    {
        using (SqlConnection cn = new SqlConnection(_connectionString))
        {
             cn.Open();
             // some select
        }
    }
}

我正在使用 Autofac 来注入(inject)该类:

var builder = new ContainerBuilder();
builder.RegisterType<DataBase>().As<IDataBase>).WithParameter("connectionString", "my connection string");
var container = builder.Build();
var database = container.Resolve<IDataBase>();
var tableData1 = database.GetSomeTableData();
// change connection string ?????????????????
var tableData2 = database.GetSomeTableData();

我需要从一个数据库和另一个数据库获取表数据。注册类后如何更改连接字符串？你可以再举一个例子..

Answer 1

有很多方法可以做到这一点。一种方法是创建并注入(inject)服务，而不仅仅是普通的连接字符串。

public interface IConnectionStringProvider
{
    public string ConnectionString { get; set }
}

public class ConnectionStringProvider
{
    public string ConnectionString { get; set }
}


var builder = new ContainerBuilder();
builder.RegisterType<DataBase>()
    .As<IDataBase>);
builder.RegisterType<ConnectionStringProvider>)
    .As<IConnectionStringProvider>
    .SingleInstance();

var container = builder.Build();
var database = container.Resolve<IDataBase>();
var connStringProvider = container.Resolve<IConnectionStringProvider>();
var tableData1 = database.GetSomeTableData();
connStringProvider.ConnectionString = "...";
var tableData2 = database.GetSomeTableData();

数据库将使用该服务:

public class DataBase : IDataBase    
{
    private readonly IConnectionStringProvider _connectionStringProvider;

    public DataBase(IConnectionStringProvider connectionStringProvider)
    {
        this._connectionStringProvider = connectionStringProvider;
    }

    public DataTable GetSomeTableData()
    {
        using (SqlConnection cn = new SqlConnection(_connectionStringProvider.ConnectionString))
        {
             cn.Open();
             // some select
        }
    }
}