c# - C# 转换列表

Question

I'm having trouble converting a list object back to its original type without an explicit cast. My intention is to generalize methods so I could pass in different db Types such as Person or Company. I have no problem getting the values via reflection but I need to convert the actual list back to its original type List<typeT> instead of List<object> in the method I am passing it to. I am aware of the following methods:

 SomeList.ConvertAll(x => (typeT)x);
 SomeList.Cast<typeT>().ToList();

However for these methods I will have to explicitly cast typeT. I have tried the following:

formatted1.ConvertAll(x => Convert.ChangeType(x, typeT));

and

List<dynamic> newList = new List<dynamic>();
foreach (var p in SomeList)
{
   newList.Add(Convert.ChangeType(p, typeT);
}

No success thus far. Maybe I should have another game-plan for generalizing these methods altogether. right now I'm passing the lists in as follows:

public string returnJson(List<object> entity, string someString)
{
}

score 6 · Accepted Answer

似乎使returnJson泛型可以解决大多数这些问题：

public string returnJson<T>(List<T> entity, string someString)
{
}

现在returnJson可以泛型使用，例如：

returnJson<Company>(listOfCompanies, "someString");

和

returnJson<Person>(listOfPersons, "someOtherString");

您仍然可以反映对象，但列表始终是您在编译时需要的类型的列表。无需铸造。

score 1 · Accepted Answer

Why not use generics, that way the calling function can do what it needs:

public string returnJson<T>(List<T> entity, string someString)
{
     //not sure what someString is for or why you need the type for this naming scheme

     JavaScriptSerializer jss = new JavaScriptSerializer();
     return jss.Serialize(entity);
}

score 0 · Accepted Answer

You can use the dynamic keyword and reflection to create the list.

dynamic newList = Activator.CreateInstance(typeof(List<>).MakeGenericType(typeT));
foreach (var p in SomeList)
{
   newList.Add(p);
}
CallOtherMethodOverloadedForListOfPersonCompanyEtc(newList)

3 回答 3

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