将动态类型的实例传递给泛型类中的泛型方法 [英] Passing an instance of a dynamic type to a generic method in a generic class

问题描述

我有一个公开泛型方法的泛型类.此方法接收泛型对象的实例作为参数并修改此实例.

I have a generic class that exposes a generic method. This method receives an instance of the generic object as parameter and modifies this instance.

示例类:

public class GenericClass<T>
{
    public T GenericMethod(T obj)
    {
        // modify the object in some (arbitrary) way
        IEnumerable<FieldInfo> fields = obj.GetType().GetRuntimeFields();
        foreach (FieldInfo field in fields)
        {
            if (field.FieldType == typeof(string))
            {
                field.SetValue(obj, "This field's string value was modified");
            }
        }

        return obj;
    }
}

如果我有一个类型(abc):

If I have a type (abc):

public class abc
{
    public string a;
    public string b;
    public int c;
}

我可以这样调用这个方法:

I can call this method as follows:

GenericClass<abc> myGeneric = new GenericClass<abc>();
var myObject = myGeneric.GenericMethod(new abc());

//Confirm success by printing one of the fields
Console.Writeline(((abc)myObject).a);

现在，我的实际问题是:

我将如何使用仅在运行时已知的类型(而不是上面的类型 abc)来调用相同的泛型方法.我还想在将它传递给 GenericMethod 时将其实例化，就像我在上面为 abc 所做的那样.

How would I call this same Generic method, using a type that is only known at run-time (as opposed to type abc above). I also want to instantiate this this as I pass it in to the GenericMethod, just like I did for abc above.

例如(我知道这是完全错误的)

Type MyType;

GenericClass<MyType> myGeneric = new GenericClass<MyType>();
var myObject = myGeneric.GenericMethod(new MyType());

由于未知类型的成功无法通过打印可能不存在的字段a"来确认，我可以打印所有字符串字段的值，但这超出了问题的范围.

推荐答案

回答您的问题:

var type = typeof(abc);
object instanceToModify = new abc();

var typeToCreate = typeof(GenericClass<>).MakeGenericType(type);
var methodToCall = typeToCreate.GetMethod("GenericMethod");

var genericClassInstance = Activator.CreateInstance(typeToCreate);
methodToCall.Invoke(genericClassInstance, new[] { instanceToModify });

演示

但是:

如果您的类型仅在运行时已知，您的实例必须在声明为 object 或 dynamic 的变量中处理.在这种情况下，您可以将方法签名更改为:

If your type is only known at runtime your instance must be handled in a variable declared as object or dynamic. In that case you can change your method signature to:

public object GenericMethod(object obj)
{
    // modify the object in some (arbitrary) way
    IEnumerable<FieldInfo> fields = obj.GetType().GetRuntimeFields();
    foreach (var field in fields)
    {
        if (field.FieldType == typeof(string))
        {
            field.SetValue(obj, "This field's string value was modified");
        }
    }

    return obj;
}

不需要通用的类/方法.

There's no need for a generic class/method.

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