在多租户环境中解决正确接口实现的策略

给定此接口：

public interface ILoanCalculator
{
    decimal Amount { get; set; }
    decimal TermYears { get; set; }
    int TermMonths { get; set; }
    decimal IntrestRatePerYear { get; set; }
    DateTime StartDate { get; set; }
    decimal MonthlyPayments { get; set; }
    void Calculate();
}

和它的 2 个暗示：

namespace MyCompany.Services.Business.Foo
{
    public interface ILoanCalculator : Common.ILoanCalculator
    {
    }
    public class LoanCalculator : ILoanCalculator
    {
        public decimal Amount { get; set; }
        public decimal TermYears { get; set; }
        public int TermMonths { get; set; }
        public decimal IntrestRatePerYear { get; set; }
        public DateTime StartDate { get; set; }
        public decimal MonthlyPayments { get; set; }
        public void Calculate()
        {
            throw new NotImplementedException();
        }
    }
}
namespace MyCompany.Services.Business.Bar
{
    public interface ILoanCalculator : Common.ILoanCalculator
    {
    }
    public class LoanCalculator : ILoanCalculator
    {
        public decimal Amount { get; set; }
        public decimal TermYears { get; set; }
        public int TermMonths { get; set; }
        public decimal IntrestRatePerYear { get; set; }
        public DateTime StartDate { get; set; }
        public decimal MonthlyPayments { get; set; }
        public void Calculate()
        {
            throw new NotImplementedException();
        }
    }
}

给定上面的简单代码，假设计算方法的实现因公司而异。在初始化期间加载程序集并调用正确程序集的正确方法的正确方法是什么？我已经弄清楚了最简单的部分是确定请求适用于哪家公司，现在我只需要调用与当前业务相对应的正确方法。

谢谢斯蒂芬

更新的示例代码

@Scott大喊大叫，以下是我必须进行的更改，以使接受的答案正常工作。

在这种情况下，我必须使用程序集解析程序来查找我的类型。请注意，我使用了一个属性来标记我的程序集，以便基于它的筛选更简单且不易出错。

public T GetInstance<T>(string typeName, object value) where T : class
{
    // Get the customer name from the request items
    var customer = Request.GetItem("customer") as string;
    if (customer == null) throw new Exception("Customer has not been set");
    // Create the typeof the object from the customer name and the type format
    var assemblyQualifiedName = string.Format(typeName, customer);
    var type = Type.GetType(
        assemblyQualifiedName,
        (name) =>
        {
            return AppDomain.CurrentDomain.GetAssemblies()
                .Where(a => a.GetCustomAttributes(typeof(TypeMarkerAttribute), false).Any()).FirstOrDefault();
        },
        null,
        true);
    if (type == null) throw new Exception("Customer type not loaded");
    // Create an instance of the type
    var instance = Activator.CreateInstance(type) as T;
    // Check the instance is valid
    if (instance == default(T)) throw new Exception("Unable to create instance");
    // Populate it with the values from the request
    instance.PopulateWith(value);
    // Return the instance
    return instance;
}

标记属性

[AttributeUsage(AttributeTargets.Assembly)]
public class TypeMarkerAttribute : Attribute { }

插件组装中的用法

[assembly: TypeMarker]

最后，对静态 MyType 稍作更改以支持限定名称

public static class MyTypes
{
    // assemblyQualifiedName
    public static string LoanCalculator = "SomeName.BusinessLogic.{0}.LoanCalculator, SomeName.BusinessLogic.{0}, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null";
}