C＃静态类型不能用作参数

public static void SendEmail(String from, String To, String Subject, String HTML, String AttachmentPath = null, String AttachmentName = null, MediaTypeNames AttachmentType = null)
{
    ....

    // Add an attachment if required
    if (AttachmentPath != null)
    {
        var ct = new ContentType(MediaTypeNames.Text.Plain);
        using (var a = new Attachment(AttachmentPath, ct)
                    {
                        Name = AttachmentName,
                        NameEncoding = Encoding.UTF8,
                        TransferEncoding = TransferEncoding.Base64
                    })
        {
            mailMessage.Attachments.Add(a);
        }
    }

    ....
}

As you can see the MediaTypeNames AttachmentType throws the error:

如您所见，MediaTypeNames AttachmentType会引发错误：

'System.Net.Mime.MediaTypeNames': static types cannot be used as parameters

What is the best way to deal with this?

处理这个问题的最佳方法是什么？

7 个解决方案

#1

You can't pass a static type to a method as a parameter because then it would have to be instantiated, and you can't create an instance of a static class.

您不能将静态类型作为参数传递给方法，因为它必须实例化，并且您不能创建静态类的实例。

#2

It's not recommended but you can simulate use of Static classes as parameters. Create an Instance class like this :

不建议这样做，但您可以模拟使用静态类作为参数。创建一个这样的Instance类：

public class Instance
{

    public Type StaticObject { get; private set; }

    public Instance(Type staticType)
    {
        StaticObject = staticType;
    }

    public object Call(string name, params object[] parameters)
    {
        MethodInfo method = StaticObject.GetMethod(name);
        return method.Invoke(StaticObject, parameters);
    }

    public object Call(string name)
    {
        return Call(name, null);
    }

}

Then your function where you would use the static class :

然后你的函数将使用静态类：

    private static void YourFunction(Instance instance)
    {
        instance.Call("TheNameOfMethodToCall", null);
    }

For instance.Call :

例如。电话：

The first parameter is the name of the method of your static class to call
第一个参数是要调用的静态类的方法的名称
The second parameter is the list of arguments to pass to the method.
第二个参数是要传递给方法的参数列表。

And use like this :

并使用这样的：

    static void Main(string[] args)
    {

        YourFunction(new Instance(typeof(YourStaticClass)));

        Console.ReadKey();

    }

#3

You can wrap static types around and interface or another non-static class and add that as the parameter. Not ideal but a way around it. Or simply just reference the static type in the method body itself

您可以包装静态类型和接口或另一个非静态类，并将其添加为参数。不理想，但绕过它。或者只是简单地引用方法体本身中的静态类型

#4

Use a different type for the argument.

为参数使用不同的类型。

A method argument need to be of a type that can accept a reference to an instance, so it can't be a static class.

方法参数必须是可以接受对实例的引用的类型，因此它不能是静态类。

#5

The best deal is definitely to remove the last parameter. Since type is static you don't need a reference to an instance and you can refer to its members from your function body.

最好的交易肯定是删除最后一个参数。由于type是static，因此您不需要对实例的引用，您可以从函数体中引用它的成员。

#6

Send a static class as the type of the parameter and then give it a variable name for use in the function. This works because the new variable is a reference to the static class. It is necessary to address the global variable problem. If you use a static class as a variable inside a method, you need to pass it in as a parameter, to avoid the global variable issue. This is basic structured programming 101 from the 80's.

发送一个静态类作为参数的类型，然后给它一个变量名，以便在函数中使用。这是有效的，因为新变量是对静态类的引用。有必要解决全局变量问题。如果在方法中使用静态类作为变量，则需要将其作为参数传递，以避免全局变量问题。这是80年代的基本结构化编程101。

#7

It doesn't look like you even use that parameter in your method. You should just remove it because MediaTypeNames cannot be instantiated anyway.

看起来你甚至不在你的方法中使用该参数。您应该删除它，因为无论如何都无法实例化MediaTypeNames。

#1