Vb.net 随机数生成器多次生成相同的数字

Question

我有这个程序从文件中生成名字和姓氏。当我运行这个程序时，我在三个文本框中输入信息。前两个是salary low和high(salary1.text,salary2.text)，最后一个是我想要的“份数”(copies.text)..当我在文本中输入10这样的数字时框它输出一些相同的名称。

名字文件有大约 100 条记录
并且姓氏文件有大约 1000 条记录

为什么它生成相同的名称

如果我做 1000 份之类的事情，问题会更糟。它输出相同的东西 8 次，然后再做 8 次不同的东西

Public Class Form1

    Dim sex As String

Function randomfirstname()
    Dim infile As IO.StreamReader
    Dim infile1 As IO.StreamReader
    Dim male() As String
    Dim female() As String
    Dim name As String
    Dim n As Integer = 0
    Dim fun As New System.Random
    Dim maleorfemale As New Random()
    Dim RandomNumber As Integer
    Dim index As Integer
    RandomNumber = maleorfemale.Next(0, 55984)
    infile = IO.File.OpenText("boysnames.txt")
    infile1 = IO.File.OpenText("girlsnames.txt")

    If RandomNumber Mod 2 = 0 Then
        While infile.Peek <> -1
            ReDim Preserve male(n)
            male(n) = infile.ReadLine
            n = n + 1
        End While
        n = n - 1
        index = fun.Next(0, n)
        name = male(index)
        sex = "M"
        n = 0
        Return name


    Else
        While infile1.Peek <> -1
            ReDim Preserve female(n)
            female(n) = infile1.ReadLine
            n = n + 1
        End While
        n = n - 1
        index = fun.Next(0, n)
        name = female(index)
        sex = "F"
        Return name
        n = 0
    End If
End Function
Function randomlastname()
    Dim infile2 As IO.StreamReader
    Dim lname() As String
    Dim lastname As String
    Dim n As Integer = 0
    Dim index As Integer
    Dim fun As New System.Random
    infile2 = IO.File.OpenText("lastname.txt")
    While infile2.Peek <> -1
        ReDim Preserve lname(n)
        lname(n) = infile2.ReadLine
        n = n + 1
    End While
    n = n - 1
    index = fun.Next(0, n)
    lastname = lname(index)
    Return lastname
End Function
Function salary()
    Dim salary01 As Double
    Dim salary02 As Double
    Dim salary03 As Double
    salary01 = CDbl(salary1.Text)
    salary02 = CDbl(salary2.Text)
    Dim sal As New System.Random


    salary03 = System.Math.Round(sal.NextDouble() * (salary02 - salary01) + salary01, 2)
    Return salary03
End Function

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    'ListBox1.Items.Add(randomfirstname() & vbTab & randomlastname() & vbTab & sex & vbTab & salary())
    Dim outfile As New System.IO.StreamWriter("C:\Users\Johnathon\Desktop\486assign1.txt")
    Dim i As Integer = 0
    outfile.Write("Firstname" & vbTab & "LastName" & vbTab & "Sex" & vbTab & "Salary" & vbCrLf)
    outfile.Write("-----------------------------------------------------------------------------" & vbCrLf)

    For i = 1 To CInt(copies.Text)
        outfile.Write(randomfirstname() & vbTab & randomlastname() & vbTab & sex & vbTab & salary() & vbCrLf)
        ListBox1.Items.Add(randomfirstname() & vbTab & randomlastname() & vbTab & sex & vbTab & salary())
    Next
    outfile.Close()

End Sub
End Class

具有 10 条记录的示例输出

Firstname   LastName    Sex Salary
-----------------------------------------------------------------------------
Carson  Gillespie   M   8.46    
Carson  Gillespie   M   8.46
Carson  Gillespie   M   8.46
Samantha    Daniels F   5.84
Samantha    Daniels F   5.84
Samantha    Daniels F   5.84
Natalia Guthrie F   9.26
Natalia Guthrie F   9.26
Natalia Guthrie F   9.26
Natalia Guthrie F   6.64

Answer 1

您正在使用 System.Random 的新实例每次。 Random由当前时间播种。

Initializes a new instance of the Random class, using a time-dependent default seed value

Reference

由于您正在非常快速地连续创建新实例，因此它们会获得相同的种子。
相反，您应该使用 Random 的相同实例。 ，可能通过将其设为字段并初始化为字段初始值设定项或构造函数。例如:

Public Class Form1
    Private _random As New System.Random()

    'Use _random in other methods.
End Class