Question

我正在尝试根据将从用户界面检索的字符串创建一个类的实例，然后我想访问该类实例的属性。

以下是我到目前为止的概述 -

namespace MamdaAdapter
{
    public interface IExchange
    {
        string GetTransport();
    }
}


namespace MamdaAdapter
{
    public class Exchange
    {
        public class Arca : IExchange
        {
            private const string _Transport = "tportname";

            public string GetTransport()
            {
                return _Transport;
            }
        }


        public static IExchange DeriveExchange(string ExchangeName)
        {
            IExchange SelectedExchange = (IExchange)Activator.CreateInstance(Type.GetType(ExchangeName));

            return SelectedExchange;
        }
    }
}



namespace MyUserInterface
{
    public class MainForm
    {
        private void simpleButton1_Click(object sender, EventArgs e)
        {
            IExchange SelectedExchange = Exchange.DeriveExchange("Exchange.Arca");

            Console.WriteLine(SelectedExchange.GetTransport());
        }
    }
}

更新现在，我得到一个Exception，上面写着“Value not not null”，这对我来说意味着它无法在给定字符串的情况下创建类的实例 -

Answer 1

假设UI没有公开完整的类型名称，您通常需要一个字典将显示名称与类型相关联：

Dictionary<string, Type> _associations = new Dictionary<string, Type>();

然后，您只需实例化新对象：

if(_associations.ContainsKey(someString))
{
   Type selectedType = _associations[someString];

   return Activator.CreateInstance(selectedType) as IExchange;
}

throw new ApplicationException("No type defined for that string yo");

如果在编译时不知道该字符串，您基本上需要检查该类型是否存在：

var type = Type.GetType(someString);

if(type != null)
{
    // Do Stuff
}

Answer 2

此处的问题是您如何指定班级名称：

首先，指定命名空间。其次，由于Arca是一个内部类，你必须使用'+'而不是'。'

(...) = Exchange.DeriveExchange("MamdaAdapter.Exchange+Arca");

Answer 3

我写了一个小的c＃控制台应用程序来模拟你的需求，测试好了，希望它有所帮助：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MamdaAdapter;
using System.Reflection;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            IExchange SelectedExchange = Exchange.DeriveExchange("MamdaAdapter.Arca");
            Console.WriteLine(SelectedExchange.GetTransport());
        }
    }
}

namespace MamdaAdapter
{
    public interface IExchange
    {
        string GetTransport();
    }
}


namespace MamdaAdapter
{
    public class Arca : IExchange
    {
        private const string _Transport = "tportname";

        public string GetTransport()
        {
            return _Transport;
        }
    }
}

namespace MamdaAdapter
{
    public class Exchange
    {
        public static IExchange DeriveExchange(string ExchangeName)
        {
            IExchange SelectedExchange = (IExchange)Assembly.GetAssembly(typeof(IExchange)).CreateInstance(ExchangeName, false, BindingFlags.CreateInstance, null, null, null, null);
            return SelectedExchange;
        }
    }

}

Answer 4

如果您要查找的Type未在执行Type.GetType的同一程序集中定义，则必须使用AssemblyQualifiedName（类似MyNamespace.MyClass，MyAssembly，Version = 1.3.0.0，Culture = neutral，PublicKeyToken = b17a5c561934e089）），即使FullName也不够。否则，您可以首先获取包含该类的程序集，然后执行Assembly类的GetType方法。

C＃在给定接口的情况下从String实例化类

4 个答案: