如何动态实例化对象？ [英] How can I dynamically instance an Object?

问题描述

我正在尝试构建一个工厂类，该工厂类将为我提供不同DbContext的单例化实例。

I am trying to build a factory class that will feed me singleton-ized instances of different DbContexts.

主要思想是使 Dictionary< Type，DbContext> 将容纳我需要的所有实例，以及 GetDbContext（Type type）方法，该方法在字典并返回（如果已存在）。如果没有，则应该创建一个新的Type（）并将其添加到相应的字典中。

The main idea is to have a Dictionary<Type,DbContext>that will hold all the instances I need , and a GetDbContext(Type type) method that looks up type in the dictionary and returns it if it already exists. If it doesn't it should create a new Type(), and add it to the corresponding dictionary.

我不知道该怎么做 contexts.Add（type，new type（））;

public class DbContextFactory
{
    private readonly Dictionary<Type, DbContext> _contexts;
    private static DbContextFactory _instance;

    private DbContextFactory()
    {
        _contexts= new Dictionary<Type, DbContext>();
    }

    public static DbContextFactory GetFactory()
    {
        return _instance ?? (_instance = new DbContextFactory());
    }

    public DbContext GetDbContext(Type type)
    {
        if (type.BaseType != typeof(DbContext))
            throw new ArgumentException("Type is not a DbContext type");

        if (!_contexts.ContainsKey(type))
            _contexts.Add(type, new type()); //<--THIS is what I have now Idea how to do

        return _contexts[type];
    }
}

推荐答案

制作它是一种通用方法：

Make it a generic method:

public DbContext GetDbContext<T>() where T : new()
{
    if (typeof(T).BaseType != typeof(DbContext))
        throw new ArgumentException("Type is not a DbContext type");

    if (!_contexts.ContainsKey(type))
        _contexts.Add(typeof(T), new T());

    return _contexts[type];
}

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