将动态输入到< T>

问题描述：

请参阅我有一个像这样的情况......

See i have a situation like this...

object myRoledata  = List<Roles>() --> (some list or Ienumerable type)

现在我已经从列表&LT; T&GT; -
这样的事情。

Now i have a generic method which creates an XML object from List<T> - Something like this..

public string GetXML<T>(object listdata)  
{  
    List<T> objLists = (List<T>)Convert.ChangeType(listData, typeof(List<T>));  
    foreach(var obj in listdata)   
    {  
        //logic to create xml  
    }  
}

现在来运行这个方法我也要做这样的：

Now in order to run this method I have to do like this:

string xml = GetXML<Roles>(myRoledata);

现在我不知道是什么键入可能会我要传递给的getXML 方法。我有一个称之为的getXML 不同的键入取值例如方法角色，用户等

Now i dont know what Type may come to me to be passed to GetXML method. I have a method which will call GetXML for different Types e.g. Roles, Users etc

现在我可以得到键入的列表与LT内;&GT; 像这样

now i can get the Type within the List<> like this

Type genericType = obj.GetType().GetGenericArguments()[0];

但不能通过它像这样

but cannot pass it like this

string xml = GetXML<genericType>(myRoledata);

反正我在其中可以通过任何 genericTypes 到的getXML 方法？

答

这是一个问题，你可能想的避免的解决。它的是的可能，通过反射，动态调用方法，而静态地解决这些问题 - 但它种违背了类型标注整点

This is a problem you probably want to avoid solving. It is possible, via reflection, to call methods dynamically without statically resolving them - but it kind of defeats the whole point of the type-annotations.

做这一点：

public string GetXML(IEnumerable listdata) {  
    foreach(object obj in listdata)   
        //logic to create xml  
}

...你现在可以与任何的IEnumerable 打电话或写出来的现代的方式：

... which you now can call with any IEnumerable, or write it the "modern" way as:

public string GetXML(IEnumerable<object> listdata) {  
    foreach(object obj in listdata)   
        //logic to create xml  
}

...您可以通过的getXML任何的IEnumerable 调用（ someEnumerable.Cast&LT;对象>（）），并在C＃4.0甚至直接由协方差

... which you can call with any IEnumerable via GetXML(someEnumerable.Cast<object>()) and in C# 4.0 even directly by covariance.

如果你需要一个元素运行时的类型，你可以得到它使用 .GetType（）每个元素，或者你可以通过它作为一个参数（并提供向后兼容的覆盖）：

If you need the type of an element runtime, you can get it using .GetType() on each element, or you can just pass it in as a parameter (and provide an override for backwards-compatibility):

public string GetXML(Type elementType, IEnumerable<object> listdata) {  
    foreach(object obj in listdata)   
        //logic to create xml  
}

public string GetXML<T>(IEnumerable<T> listdata) {
    return GetXML(typeof(T),listdata.Cast<object>());
}

顺便说一下，如果你正在构造XML，字符串可能是一个不太可靠返回式的选择：如果可能的话，你可以用类似的工作的XElement 而不是 - 并获得XML的有效性保证的引导

Incidentally, if you're constructing XML, a string is probably a less robust return-type choice: if possible, you could work with something like an XElement instead - and get xml-validity guarantee's to boot.

将动态输入到< T>

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