将IEnumerable转换为IEnumerable< T>当T直到运行时才知道 [英] Convert IEnumerable to IEnumerable<T> when T isn't known until runtime

问题描述

当T直到运行时才知道T时，如何将 IEnumerable 转换为 IEnumerable< T> p>

我有一个方法，它绝对需要一个 IEnumerable< T> / strong>和 T 必须是实际类型，而不是类似对象的祖先类型

。

我打赌反射API允许这样的事情，但我不知道具体如何。

更新

我可以得到这样的类型对象：

  var first = results.Cast< object>（）。 FirstOrDefault（）; 
 if（first！= null）
 {
 var type = first.GetType（）; 
 
 
 
 
 $ h2 Update2  
 
 
我所指的方法实际上是WPF DataGrid的ItemSource属性的Setter。 
我遇到的问题是，如果我没有给它传递 IEnumerable< T> ，Datagrid中生成的行都是空白的，就好像它是反映 T 属性的方法不起作用，它不能生成列。
 
 
 
即使使用这个代码有这种不必要的效果： 
 
 
  public CollectionResultWindow（IEnumerable结果）
 {
 Contract.Requires（results ！= null，结果为空。 
 
 InitializeComponent（）; 
 DataContext = this; 
 
 var first = results.Cast< object>（）。FirstOrDefault（）; 
 if（first！= null）
 {
 Type type = first.GetType（）; 
 var castMethod = typeof（Enumerable）.GetMethod（Cast）。MakeGenericMethod（type）; 
 dynamic genericResults = castMethod.Invoke（null，new [] {results}）; 
结果= genericResults; //结果是DataGrid.ItemSource绑定的依赖项属性。 
} 
 
} 
  
 
 
解决方案
 
  var elementType = ... 
 var results = ... 
 var castMethod = typeof（Enumerable）.GetMethod（Cast）。MakeGenericMethod（elementType ）; 
 var genericResults = castMethod.Invoke（null，new [] {results}）; 
  
  genericResults 变量指向键入 IEnumerable< T> （其中 T 是由 elementType 变量）。但请记住，静态地， genericResults 仍然是类型 object ;没有办法告诉编译器它是 IEnumerable< T> ，因为 T 不是静态的。
 
How can I convert IEnumerable to IEnumerable<T> when T isn't known until runtime?

I have a method that absolutely needs an IEnumerable<T> where T isn't known until runtime and T must be the actual type and not an ancestor type like object.

I'm betting the reflection API allows for something like this but I don't know exactly how.

Update

I can get a type object like this:
var first = results.Cast<object>().FirstOrDefault();
if (first != null)
{
    var type = first.GetType();

}


Update2

The "method" I was referring to was actually the Setter of the WPF DataGrid's ItemSource property.
The problem I'm having is that if I don't pass it an IEnumerable<T> the rows generated in the Datagrid are all blank, as if it's method of reflecting over the properties of T is not working and it can't generate columns.

Even using this code has this unwanted effect:
    public CollectionResultWindow(IEnumerable results)
    {
        Contract.Requires(results != null, "results is null.");

        InitializeComponent();
        DataContext = this;

        var first = results.Cast<object>().FirstOrDefault();
        if (first != null)
        {
            Type type = first.GetType();
            var castMethod = typeof(Enumerable).GetMethod("Cast").MakeGenericMethod(type);
            dynamic genericResults = castMethod.Invoke(null, new[] { results });
            Results = genericResults; // Results is a dependency property that DataGrid.ItemSource is bound to.
        }

    }

解决方案
var elementType = ...
var results = ...
var castMethod = typeof(Enumerable).GetMethod("Cast").MakeGenericMethod(elementType);
var genericResults = castMethod.Invoke(null, new[] { results });
The genericResults variable refers to an object of type IEnumerable<T> (where T is the type represented by the elementType variable). But keep in mind that statically, genericResults is still of type object; there is no way to tell the compiler that it is an IEnumerable<T>, since T isn't known statically.

                        
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