我作为学校的作业在日志上工作，我已经到了如下所示。我正在努力解决一些需要实施的问题，我最关心的是理解为什么我需要列表中的数组。
我被告知要使用：
List logBook = new List { };
string[]post = new string [2]
我的功能是，我想能够保存新帖子，至少包含一个标题和一条消息。日志被假定为List，并且每个日志都被假定为一个数组。
所以我的问题就是我正朝着正确的方向前进，有人请帮助我理解为什么它必须是列表中的数组。另外，在搜索部分时，请随时帮助我找到正确的方向，我希望能够在帖子中搜索日期，标题或单个单词。
static void Main(string[] args) {
string titel;
string post;
string[] logg = new string[20];
List<string[]> logBook = new List<string[]> { };
DateTime tiden = DateTime.Now;
Console.WriteLine(tiden.ToShortDateString());
bool go = true;
while (go)
try
{
Console.WriteLine("\n\tWelcome to the Logbook!\n");
Console.WriteLine("\t[1] Write a new post");
Console.WriteLine("\t[2] Search for a post");
Console.WriteLine("\t[3] Display all posts");
Console.WriteLine("\t[4] Quit");
Console.Write("\n\tSelect from menu: ");
int menyVal = Convert.ToInt32(Console.ReadLine());
int i = 0;
switch (menyVal)
{
case 1:
Console.WriteLine("\tWrite a title to your post: ");
titel= Console.ReadLine();
Console.WriteLine("\n\tWrite your post: ");
Console.WriteLine("\t" + tiden.ToShortDateString() + "\n");
Console.WriteLine("\t" + titel + "\t");
post = Console.ReadLine();
logg[i] = tiden.ToShortDateString() + "\n" + titel + "\n" + post + "\n";
logBook.Add(logg);
i = i + 1;
break;
case 2:
Console.WriteLine("\tWrite a searchword or a date (yyyy-mm-dd)");
string keyword = Console.ReadLine();
foreach (var item in logBook)
{
if (logg[i] == keyword)
Console.WriteLine(logg[i]);
else
Console.WriteLine("Searchword couldn't be found.");
}
break;
case 3:
Console.WriteLine("\tThese are the current posts in Logbook.\n ");
foreach (string[] element in logBook)
{
Console.WriteLine("\t" + element);
}
break;
default:
Console.WriteLine("\tChoose from menu 1 - 4");
break;
case 4:
go = false;
break;
}
}
catch
{
Console.WriteLine("\tChoose from menu 1 - 4");
}
}
}
答案 0 :(得分：3)
使用List<T>的想法是正确的。使用两个字符串数组的想法，一个用于标题，一个用于消息，是不正确的。
虽然C＃允许您将数组存储在列表中，但存储双元素数组的问题是这些数组的内容不对称：logBook[i][0]始终是标题，而logBook[i][1]始终是一条消息。
最好为帖子创建一个具有Title和Message属性的类，并使用它而不是数组：
class LogPost {
public string Title { get; set; }
public string Message { get; set; }
}
List<LogPost>比List<string[]>更具可读性，它让您以更易读的方式访问logBook[i].Title和logBook[i].Message。
答案 1 :(得分：1)
像dasblinkenlight所说，使用课程更好。所以我完全赞同他。
但....为您的解决方案。您的列表和数组存在问题。
您实现它的方式是，您使用的是字符串数组和列表。您将整个格式化字符串写为数组的一个元素。然后将整个数组添加到列表中。所以列表中的每个项目都是相同的数组......
就我阅读你的帖子而言，每个列表项应该有一个新的数组。我以一段代码为例：
> 1 + [2,3,4]
<interactive>:8:1: error:
• Non type-variable argument in the constraint: Num [t]
(Use FlexibleContexts to permit this)
• When checking the inferred type
it :: forall t. (Num [t], Num t) => [t]
> 1 + sum [2,3,4]
10
这样就不需要全局switch (menyVal)
{
case 1:
Console.WriteLine("\tWrite a title to your post: ");
// i'd rather declare the string here, so the code and declaration should stick together. (it's not the pascal language ;-))
string titel= Console.ReadLine();
Console.WriteLine("\n\tWrite your post: ");
Console.WriteLine("\t" + tiden.ToShortDateString() + "\n");
Console.WriteLine("\t" + titel + "\t");
post = Console.ReadLine();
// here comes the thing:
// you are formatting it as one element and add that element to the list.
// ->> wrong >> logg[i] = tiden.ToShortDateString() + "\n" + titel + "\n" + post + "\n";
// ->> logBook.Add(logg);
// create an array per item....
string[] arr = new string[2];
arr[0] = title;
arr[1] = post;
logBook.Add(arr);
// i = i + 1; not needed.
break;
数组。该列表将保留对您添加的数组的引用。
这是不正确的......你迭代日志（数组列表）并且你反复检查相同的logitem。 （变量logg永远不会改变）
i您正在寻找的是：
foreach (var item in logBook)
{
if (logg[i] == keyword)
Console.WriteLine(logg[i]);
else
Console.WriteLine("Searchword couldn't be found.");
}
或简而言之：
van anyFound = false;
foreach (var item in logBook)
{
foreach(var element in item)
{
if(element == keyword)
{
foreach(var s in item)
{
Console.Write(s);
}
Console.WriteLine("");
anyFound = true;
}
}
if(!anyFound)
Console.WriteLine("Searchword couldn't be found.");
}
随时提出更多信息
答案 2 :(得分：0)
即使我没有通过编辑或更改日志来解决问题，甚至删除日志，这也是最终归结为......我明天可能会这样做： ）
List<string[]> logBook = new List<string[]> { };
DateTime time = DateTime.Now;
Console.WriteLine("\t" + time.ToShortDateString());
Console.WriteLine("\n\tWelcome to the Logbook!\n");
bool go = true;
while (go)
try
{
{
Console.WriteLine(""); //Skapar ny rad. Användaren ska inte känna att det blandar ihop sig.
Console.WriteLine("\t[1] Write a new post");
Console.WriteLine("\t[2] Search for a post");
Console.WriteLine("\t[3] Display all posts");
Console.WriteLine("\t[4] Quit");
Console.Write("\n\tSelect from menu: ");
int menu = Convert.ToInt32(Console.ReadLine()); //Gör om inmatad sträng till heltal.
Console.WriteLine(""); //Skapar mellanrum innan nästa direktiv till användaren (Estetiskt).
switch (menu)
{
case 1:
string timeDate = time.ToShortDateString();
Console.Write("\tWrite a title to your post: ");
string title = Console.ReadLine();
Console.Write("\n\tPost is created " + timeDate + "\n\n\tWrite your post: ");
//Console.WriteLine("\t" + timeDate + "\n");
//Console.WriteLine("\t" + title + "\n\t");
string post = Console.ReadLine();
string[] arr = new string[3];
arr[0] = timeDate;
arr[1] = title;
arr[2] = post;
logBook.Add(arr);
break;
case 2:
Console.Write("\tWrite a searchword or a date (yyyy-mm-dd): ");
string keyword = Console.ReadLine();
Console.WriteLine("");
bool anyFound = false;
foreach (string[] item in logBook) //För varje element(item) i Listan(logBook) dvs (arr[i])
{
foreach (string element in item) //För varje element(element) i arr[i] dvs (arr[0], arr[1], arr[2])
{
if (element.Contains(keyword)) // Om arr[0], arr[1] eller arr[2] innhåller sökord....
{
foreach (string s in item) // Skriv ut varje arr[i] i det elementet(item) (dvs hela den loggen)
{
Console.WriteLine("\t" + s);
}
Console.WriteLine("");
anyFound = true;
}
}
}
if (!anyFound)
Console.WriteLine("\tSearchword couldn't be found.");
break;
case 3:
Console.WriteLine("\tThese are the current posts in Logbook.\n ");
foreach (var item in logBook) //För varje element(item) i Listan(logBook) dvs (arr[i])
{
foreach (string element in item) //För varje element(element) i arr[i] dvs (arr[0], arr[1], arr[2])
{
Console.WriteLine("\t" + element);
}
Console.WriteLine("");
}
break;
default:
Console.WriteLine("\tChoose from menu 1 - 4");
break;
case 4:
go = false;
break;
}
}
}
catch
{
Console.WriteLine(""); //Estetisk för att användaren ska få ny rad innan meddelandet.
Console.WriteLine("\tChoose from menu by using number 1 - 4"); //Aktiveras om användaren knappar in annat än heltal.
}