将未知类型的列表转换为通用列表类型

Question

I'm processing a lot of FieldInfo information and I want to add exceptions for certain types of data to process them differently (To make a neat output string) but I can't find a way to cast the object to a List so I can get the count from it.

My code:

string str = "";
string value = "";

foreach (FieldInfo fieldInfo in fieldInfos)
{
    if (fieldInfo.Name == "Sprite" || fieldInfo.Name == "Background")
    {
        value = "Unreadable";
    }
    else if (fieldInfo.GetValue(type) == null)
    {
        value = "Null";
    }
    else
    {
        switch (fieldInfo.GetValue(type).GetType().Name)
        {
            default:
                value = fieldInfo.GetValue(type).ToString();
                break;
            case "Color":
                value = ((Color)fieldInfo.GetValue(type)).Name;
                break;
            case "List`1":
                value = (((System.Collections.Generic.List<>)fieldInfo.GetValue(type)).Count - 1).ToString();
                break;
        }
    }

    str += "        " + fieldInfo.Name + ": " + value + Environment.NewLine;
}
return str;

Answer 1

Cast it to non-generic ICollection instead:

(((System.Collections.ICollection)fieldInfo.GetValue(type)).Count - 1).ToString();

It will give you access to Count property.

Answer 2

If you're just after the number of items then just use the non-generic IList which List<> also implements:

case "List`1":
  value = (((System.Collections.IList)fieldInfo.GetValue(type)).Count - 1).ToString();
  break;

You could add some flexibility by supporting any container by changing the default clause to this:

default:
 if (typeof(System.Collections.ICollection).IsAssignableFrom(fieldInfo.GetValue(type).GetType())
   value = (((System.Collections.ICollection)fieldInfo.GetValue(type)).Count - 1).ToString();
  else
    value = fieldInfo.GetValue(type).ToString();
  break;

Now you'll handle collections such as Dictionary<> and LinkedList<> as well as List<>