Compact Framework - 如何动态创建没有默认构造函数的类型？

发布于 2024-12-17 04:27:46 字数 360 浏览 6 评论 0原文

我正在使用.NET CF 3.5。我想要创建的类型没有默认构造函数，因此我想将字符串传递给重载的构造函数。我该怎么做？

代码：

Assembly a = Assembly.LoadFrom("my.dll");
Type t = a.GetType("type info here");
// All ok so far, assembly loads and I can get my type

string s = "Pass me to the constructor of Type t";
MyObj o = Activator.CreateInstance(t); // throws MissMethodException

原文

I'm using the .NET CF 3.5. The type I want to create does not have a default constructor so I want to pass a string to an overloaded constructor. How do I do this?

Code:

Assembly a = Assembly.LoadFrom("my.dll");
Type t = a.GetType("type info here");
// All ok so far, assembly loads and I can get my type

string s = "Pass me to the constructor of Type t";
MyObj o = Activator.CreateInstance(t); // throws MissMethodException

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月寒剑心 2024-12-24 04:27:46

MyObj o = null;
Assembly a = Assembly.LoadFrom("my.dll");
Type t = a.GetType("type info here");

ConstructorInfo ctor = t.GetConstructor(new Type[] { typeof(string) });
if(ctor != null)
   o = ctor.Invoke(new object[] { s });

MyObj o = null;
Assembly a = Assembly.LoadFrom("my.dll");
Type t = a.GetType("type info here");

ConstructorInfo ctor = t.GetConstructor(new Type[] { typeof(string) });
if(ctor != null)
   o = ctor.Invoke(new object[] { s });

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鞋纸虽美，但不合脚ㄋ〞 2024-12-24 04:27:46

好吧，这里有一个时髦的帮助器方法，它为您提供了一种灵活的方法来激活给定参数数组的类型：

static object GetInstanceFromParameters(Assembly a, string typeName, params object[] pars) 
{
    var t = a.GetType(typeName);

    var c = t.GetConstructor(pars.Select(p => p.GetType()).ToArray());
    if (c == null) return null;

    return c.Invoke(pars);
}

您可以这样调用它：

Foo f = GetInstanceFromParameters(a, "SmartDeviceProject1.Foo", "hello", 17) as Foo;

因此，您将程序集和类型名称作为前两个参数传递，然后将所有参数传递给它。构造函数的参数按顺序排列。

Ok, here's a funky helper method to give you a flexible way to activate a type given an array of parameters:

static object GetInstanceFromParameters(Assembly a, string typeName, params object[] pars) 
{
    var t = a.GetType(typeName);

    var c = t.GetConstructor(pars.Select(p => p.GetType()).ToArray());
    if (c == null) return null;

    return c.Invoke(pars);
}

And you call it like this:

Foo f = GetInstanceFromParameters(a, "SmartDeviceProject1.Foo", "hello", 17) as Foo;

So you pass the assembly and the name of the type as the first two parameters, and then all the constructor's parameters in order.

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瑕疵 2024-12-24 04:27:46

看看这是否适合您（未经测试）：

Type t = a.GetType("type info here");
var ctors = t.GetConstructors();
string s = "Pass me to the ctor of t";
MyObj o = ctors[0].Invoke(new[] { s }) as MyObj;

如果该类型有多个构造函数，那么您可能需要做一些花哨的步骤来找到接受字符串参数的构造函数。

编辑：刚刚测试了代码，它可以工作。

编辑2：克里斯的回答< /a> 显示了我所说的花式步法！ ;-)

See if this works for you (untested):

Type t = a.GetType("type info here");
var ctors = t.GetConstructors();
string s = "Pass me to the ctor of t";
MyObj o = ctors[0].Invoke(new[] { s }) as MyObj;

If the type has more than one constructor then you may have to do some fancy footwork to find the one that accepts your string parameter.

Edit: Just tested the code, and it works.

Edit2: Chris' answer shows the fancy footwork I was talking about! ;-)

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