C# 静态类型不能用作参数
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C# Static types cannot be used as parameters
提问by Tom Gullen
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 AttachmentTypethrows the error:
如您所见，MediaTypeNames AttachmentType抛出错误：
'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？
采纳答案by aqwert
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 staticclass.
您不能将静态类型作为参数传递给方法，因为这样就必须对其进行实例化，并且您无法创建static类的实例。
回答by Primary Key
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。由于类型是静态的，您不需要对实例的引用，您可以从函数体中引用其成员。
回答by aqwert
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
您可以将静态类型包装在接口或其他非静态类周围，并将其添加为参数。不理想，而是一种解决方法。或者只是简单地引用方法体本身中的静态类型
回答by Andrew Cooper
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。
回答by Andrew Cooper
It doesn't look like you even use that parameter in your method. You should just remove it because MediaTypeNamescannot be instantiated anyway.
看起来您甚至没有在方法中使用该参数。您应该删除它，因为MediaTypeNames无论如何都无法实例化。
回答by csblo
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。创建一个这样的实例类：
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 :
然后是您将使用静态类的函数：
private static void YourFunction(Instance instance)
{
instance.Call("TheNameOfMethodToCall", null);
}
For instance.Call :
例如.Call：
- The first parameter is the name of the method of your static class to call
- The second parameter is the list of arguments to pass to the method.
- 第一个参数是要调用的静态类的方法的名称
- 第二个参数是传递给方法的参数列表。
And use like this :
并像这样使用：
static void Main(string[] args)
{
YourFunction(new Instance(typeof(YourStaticClass)));
Console.ReadKey();
}
回答by Nikolai
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供在函数中使用。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入，以避免全局变量问题。这是 80 年代的基本结构化编程 101。
