c# - CS0246 : The type or namespace name `T' could not be found. 是否缺少 using 指令或程序集引用？在 C# 中

Question

我正在使用 C# 并且是初学者。我在创建霍夫曼树的情况下计算二进制文件中符号的频率(我的意思是符号重复的次数是频率)。我试图让这个“符号”适用于所有数据类型喜欢int , short , ulong等等。我这样做是使用泛型。

然后我尝试运行代码，但出现 4 个错误，例如:

CS0246: The type or namespace name `T' could not be found. Are you missing a using directive or an assembly reference?

我知道编译器无法识别这个“T”但在“T”之前我只使用了public class Node<K>而不是 public class Node<T> where T : K所以那个时候的错误是:

z.cs(13,23): warning CS0693: Type parameter `K' has the same name as the type parameter from outer type `shekhar_final_version_Csharp.Huffman<K>'
z.cs(10,18): (Location of the symbol related to previous warning)

所以我不得不用等效的“K”替换这个“T”。但是现在错误增长到 4(类似):

z.cs(20,21): error CS0246: The type or namespace name `T' could not be found. Are you missing a using directive or an assembly reference?
z.cs(72,38): error CS0246: The type or namespace name `T' could not be found. Are you missing a using directive or an assembly reference?
z.cs(83,21): error CS0246: The type or namespace name `T' could not be found. Are you missing a using directive or an assembly reference?
z.cs(267,40): error CS0246: The type or namespace name `T' could not be found. Are you missing a using directive or an assembly reference?

我的完整代码是:

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class Huffman<K> where K :  IComparable<K>
{
    public int data_size, length, i, is_there;
Line 13: public class Node<T> where T : K
    {
        public Node<T> next, left, right;
        public K symbol;
        public int freq;
        public int is_processed;
    }
Line 20: public Node<T> front, rear;
    ///////////////////////////////////////////////
    public Huffman(string[] args) 
    {
        front = null;
        rear = null;
        using(var stream = new BinaryReader(System.IO.File.OpenRead(args[0]))) 
        {
            while (stream.BaseStream.Position < stream.BaseStream.Length) 
            {
                int processingValue = stream.ReadByte(); 
                {
                    Node<T> pt, temp;
                    bool is_there = false;
                    pt = front;
                    while (pt != null) 
                    {
                        if (pt.symbol == processingValue) 
                        {
                            pt.freq++;
                            is_there = true;

                            break;
                        }
                        temp = pt;
                        pt = pt.next;
                    }
                    if (is_there == false) 
                    {
                        temp = new Node<T>();
                        temp.symbol = processingValue;
                        temp.freq = 1;
                        temp.left = null;
                        temp.right = null;
                        temp.next = null;
                        temp.is_processed = 0;
                        if (front == null) 
                        {
                            front = temp;
                        } 
                        else 
                        {
                            temp.next = front;
                            front = temp;
                        }
                    }
                }
            }
            stream.Close();
            //////////////////////////////
        }
    }
}

有人可以帮我消除这些错误吗？我真的很感激。但请记住，如果我在第 13 行中使用“public class Node<K>”而不是“public class Node<T> where T : K”。它会给出以下错误:

z.cs(13,23): warning CS0693: Type parameter `K' has the same name as the type parameter from outer type `shekhar_final_version_Csharp.Huffman<K>'
z.cs(10,18): (Location of the symbol related to previous warning) 

Answer 1

让我们看一下这个大大简化的版本:

public class Huffman<K>
{
    public class Node<T> where T : K
    {
    }

    public Node<T> front, rear;
}

front 的类型是什么？和 rear这里？它指的是T , 但我们不知道是什么 T是。 T是 Node<T> 中的类型参数 , 但是当你有一个字段的声明时，你需要提供一个类型参数。

我怀疑你真的想要:

public Node<K> front, rear;

老实说，不清楚您是否需要 Node成为一个通用类。我怀疑您可能会觉得:

public class Huffman<K>
{
    public class Node
    {
        // You can still use K here...
    }

    public Node front, rear;
}

想想你是否真的需要两个不同类型的参数 - 这样做有什么好处？