使用存储在二维数组中的相关数据

Question

我正在努力理解数组并阅读这个主题,但是当你刚刚开始编程并且没有人可以要求解释时,大部分文献都不容易理解.这是我的二维数组:

        'Declare 2-diensional array of Strings
    Dim cars(,) As String =
    New String(,) {{"BMW", "Coupe", "Reg:2015", "5 Door"},
           {"Ford", "Focus", "Reg:2015", "3 Door"},
           {"Land Rover", "Discovery", "Reg:2014", "5 Door"},
           {"Vauxhall", "Astra", "Reg:2014", "3 Door"},
           {"SEAT", "Ibiza", "Reg:2013", "5 Door"}}

    ' Get bounds of the array.
    Dim bound0 As Integer = cars.GetUpperBound(0)
    Dim bound1 As Integer = cars.GetUpperBound(1)

    ' Loop over all elements.
    For i As Integer = 0 To bound0
        For x As Integer = 0 To bound1
            ' Get element.
            Dim s1 As String = cars(i, x)
            Console.ForegroundColor = ConsoleColor.Green
            Console.Write(s1 & ", ")
        Next
        Console.WriteLine()
    Next
    Console.ReadKey()
    Console.WriteLine("Please enter the name of the record you wish to view")
    Dim s = Console.ReadLine()
    Dim value As String = Array.Find(cars, Function(x) (x.StartsWith(s)))
    Console.WriteLine(value)
    Console.ReadKey()

这是引起问题的线

Dim value As String = Array.Find(cars, Function(x) (x.StartsWith(s)))

Visual Studio建议错误是因为"无法从这些参数中推断出类型参数的数据类型.明确指定数据类型可能会纠正此错误." 我无法理解这个错误意味着什么.请有人请解释一下,好像和一个10岁的孩子交谈,或者是一个可能帮助我理解这个问题的网站.谢谢

Answer 1

关键在于数据是相关的.Class 不是将你的"汽车"拆分成碎片存储在不同的数组中,而是允许你创建一个Car对象,并将各种汽车存储在一个类型中List:

五分钟介绍Classes和Lists

Public Class Car
    Public Property Id As Int32
    Public Property Make As String
    Public Property Model As String
    Public Property Year As Int32
    '... etc
End Class

现在你有一个容器来保存一辆汽车的所有信息.这就像Car对象的外观蓝图.类还可以包含方法(Sub或Function)来管理它们存储的数据,以便与该类相关的所有与Car或Employee或Order相关的内容.

Dim c As New Car          ' create a new car object
c.Make = "Mazda"
c.Model = "Miata"
c.Year = 2013

或者在声明时初始化:

Dim c As New Car With {.Make = "Mazda", .Model = "Miata" ...}

现在,新千年版的数组,是一个List.这些更容易使用,因为它们自己的大小:

Dim Cars As New List(Of Car)

该Cars集合只能存储汽车对象,它存储的每辆汽车都会将数据保存在一起.还有许多其他集合类型,例如Dictionary您最终想要熟悉的类型.将马自达添加到列表中:

' c is the car object created above
Cars.Add(c)

与阵列不同,您无需知道将要使用多少辆汽车,因为它们会自行调整大小.引用一个,Cars(n)将引用一个汽车对象:

' n is the index of a car in the list
Dim str = Cars(n).Make & " is " & Cars(n).Color

使用临时Car变量迭代列表:

For Each c As Car In Cars   
    ' c will be Cars(0), Cars(1) etc as we step thru
    Console.WriteLine("Index {0} is a BEAUTIFUL {1} {2}",
           Cars.IndexOf(c), c.Year, c.Model)
    ' e.g
    ' "Index 4 is a BEAUTIFUL 2015 Camry"
Next

找一个或第一个:

Dim myCar = Cars.FirstOrDefault(Function (f) f.Make = "Mazda" AndAlso f.Year = 2013)

A List(Of T)可以用作DataSource某些控件:

myDGV.DataSource = Cars

在DataGridView将为每个创建一个列属性的Car类,并添加一行列表中的每个汽车对象-简单!

要么:

myListBox.DataSource
myList.DisplayMember = "Make"
myList.ValueMember = "Id"

用户将Make在ListBox(或您定义的任何内容)中看到. SelectedValue将是他们选择的汽车对象的Id,SelectedItem并将成为整个汽车对象.无需通过不同的数组来搜索相关数据 - 它总是在一个地方.