Question

我正在创建一个应用程序，它在命令行中将Tuple显示为一个表，并且需要能够按项目1对其进行过滤。我当前显示元组的实现是：

Console.Clear(); //clears the console
var file1 = @"Files\Day.txt"; //location of the Day file
var file2 = @"Files\Date.txt"; //location of the Date file
var file3 = @"Files\Value1.txt"; //location of the value1
var file4 = @"Files\Value2.txt"; //location of the value2
var file5 = @"Files\Value3.txt"; //location of the value3
var file6 = @"Files\Value4.txt"; //location of the value4

var days = System.IO.File.ReadAllLines(file1); 
var dates = System.IO.File.ReadAllLines(file2); 
var value1 = System.IO.File.ReadAllLines(file3); 
var value2 = System.IO.File.ReadAllLines(file4); 
var value3 = System.IO.File.ReadAllLines(file5); 
var value4 = System.IO.File.ReadAllLines(file6); 
var columnCount = days.Length; 
var Content = new List<Tuple<string, string, string, string, string, string>>(); // The list of items read from each file

for (int i = 0; i < columnCount; i++) // Add a new item for each line in each file
{
    Content.Add(new Tuple<string, string, string, string, string, string>(days[i], dates[i], value1[i], value2[i], value3[i], value4[i]));
}
Console.Clear();
Console.WriteLine(" - ASCENDING ORDER -----------------------------------------------------------------------------");
Console.WriteLine("| DAY          DATE         VALUE1     VALUE2      VALUE3      | VALUE4 |");
Console.WriteLine(" -----------------------------------------------------------------------------------------------");
Content = Content.OrderBy(item => item.Item2).ToList();
Content.ForEach(item => Console.WriteLine(" {0}    \t {1}   \t   {2}   \t   {3}   \t   {4}   \t   {5}", item.Item1, item.Item2, item.Item3, item.Item4, item.Item5, item.Item6));
Console.WriteLine(" ------------------------------------------------------------------------------------------------");}

等

现在我需要做的是我需要能够过滤此表，以便例如过滤item1以包含值为“Monday”的行。这就是我尝试实现过滤器的方法：

string DaySearchInput;
Console.WriteLine("\nYou may search for items on the following days;");
Console.Write("\nPlease enter the day of the week you wish to search for (case sensitive): ");
DaySearchInput= Console.ReadLine();


var daySearch = Content.Where(tuple => tuple.Item1 == DaySearchInput);
daySearch = Content.OrderByDescending(item => item.Item2).ToList();


Console.Clear();
Console.WriteLine("\n - VALUES ON A {0}     --------------------------------------------------------------------", DaySearchInput);
Console.WriteLine("| DAY               DATE         VALUE1     VALUE2           VALUE3     | VALUE4 |");
Console.WriteLine(" -----------------------------------------------------------------------------------------------");
daySearch.ForEach(item => Console.WriteLine(" {0}    \t {1}   \t   {2}   \t   {3}   \t   {4}   \t   {5}", item.Item1, item.Item2, item.Item3, item.Item4, item.Item5, item.Item6));

尝试编译当前文件时出现此错误：

'System.Collections.Generic.IEnumerable<System.Tuple<string,string,string,string,string,string>>'不包含'ForEach'的定义，也没有扩展方法'ForEach' 接受第一个类型的参数可以找到'System.Collections.Generic.IEnumerable<System.Tuple<string,string,string,string,string,string>>'（您是否缺少using指令或程序集引用？）

Answer 1

List<T>实施IEnumerable<T>。因此，当您重新分配daySearch时，它会编译。您应该引入daySearchList并使用它。

var daySearch = Content.Where(tuple => tuple.Item1 == DaySearchInput);
var daySearchList = Content.OrderByDescending(item => item.Item2).ToList();

或者只是删除你的第一个查询，因为它只是被覆盖了。

var daySearch = Content.OrderByDescending(item => item.Item2).ToList();

Answer 2

在您的daySearch声明中，您使用了var daySearch，这导致了IEnumerable，因为您没有为其分配List，只是.Where()的IEnumerable结果。使用类似的东西：

var daySearch = Content.Where(tuple => tuple.Item1 == DaySearchInput)
                 .OrderByDescending(item => item.Item2).ToList();

这应该允许您使用.ForEach扩展方法。

如何通过单个项C＃过滤元组

2 个答案: