What's the meaning of “apostrophe + number” in the object type of properties with generics (eg. “Collection`1”)?

问题

I have an object (MyObject) with a property (MyProperty). I want to get it's type name (i.e. String or MyClass etc.). I use:

PropertyInfo propInfo = typeof(MyObject).GetProperty("MyProperty");
Console.WriteLine(propInfo.PropertyType.Name);
Console.WriteLine(propInfo.PropertyType.FullName);

No problem with simple types, but when MyProperty is a generic type, I face problems on getting it's name (e.g. Collection<String>). It prints:

Collection`1

System.Collections.ObjectModel.Collection`1[[System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]

What is that `1? And how can I obtain "Collection<String>"?

回答1:

The ``1` means a generic type, with 1 generic parameter.

One way of getting the string is by using the System.CodeDom, as suggested by @LukeH:

using System;
using System.CodeDom;
using System.Collections.Generic;
using Microsoft.CSharp;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var p = new CSharpCodeProvider())
            {
                var r = new CodeTypeReference(typeof(Dictionary<string, int>));

                Console.WriteLine(p.GetTypeOutput(r));
            }
        }
    }
}

An alternative method is here. See below for @jaredpar's code:

public static string GetFriendlyTypeName(Type type) {
    if (type.IsGenericParameter)
    {
        return type.Name;
    }

    if (!type.IsGenericType)
    {
        return type.FullName;
    }

    var builder = new System.Text.StringBuilder();
    var name = type.Name;
    var index = name.IndexOf("`");
    builder.AppendFormat("{0}.{1}", type.Namespace, name.Substring(0, index));
    builder.Append('<');
    var first = true;
    foreach (var arg in type.GetGenericArguments())
    {
        if (!first)
        {
            builder.Append(',');
        }
        builder.Append(GetFriendlyTypeName(arg));
        first = false;
    }
    builder.Append('>');
    return builder.ToString();
}

回答2:

This is a CLR internal typename.

The number is the number of generic type parameters, since types can be overloaded.
(Func`1 and Func`2 are different types)

There is no built-in way to get a C#-style typename, since the CLR has nothing to do with C#.

回答3:

SLaks already explained what `1 means.

About your second question: You can obtain the name of the generic type parameters by using Type.GetGenericArguments:

if (propInfo.PropertyType.IsGenericType) {
    Type[] typeArguments = propInfo.PropertyType.GetGenericArguments();
    // typeArguments now contains an array of types ({String} in your example).
}

来源：https://stackoverflow.com/questions/6584263/whats-the-meaning-of-apostrophe-number-in-the-object-type-of-properties-wit

标签

.net

generics

reflection

fully-qualified-naming