Question

我正在开发一个将添加用户输入的vb.net 2010表单。我想制作一个可以计算总和，平均值，方差和标准偏差的程序....任何人都可以帮助添加代码并修复问题????请帮助我....我正在尝试解决问题但是当我运行程序时出现错误＆＃34; InvalidOperationException未处理（创建表单时出错。有关详细信息，请参阅Exception.InnerException。错误is：对象引用未设置为对象的实例。）＆＃34;

任何人都可以帮我解决这个问题吗？

Public Class Form1
Dim sum As Integer
Dim mean As Double
Dim x(ListBox1.Items.Count - 1) As Integer

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
    Dim TotalN As Double = InputBox("The total Number", "Enter a number")
    Dim sum As Single
    Dim b As Integer = ListBox1.Items.Count - 1

    Dim counter As Integer
    For counter = 0 To b
        x(counter) = ListBox1.Items(counter)

        If (Val(x(counter)) = TotalN) Then

            sum = (sum + x(counter)) / TotalN

        End If

    Next
End Sub
End Class

Answer 1

我认为你得到了异常，因为当ListBox不包含任何项时，x数组是在程序/表单的开头创建的。

尝试在ReDim方法中执行数组的Button1_Click。

Public Class Form1
    Dim sum As Integer
    Dim mean As Double
    Dim x(ListBox1.Items.Count - 1) As Integer

    Private Sub Button1_Click() Handles Button1.Click
        Dim TotalN As Double = InputBox("The total Number", "Enter a number")
        Dim sum As Single
        Dim b As Integer = ListBox1.Items.Count - 1

        ReDim x(ListBox1.Items.Count - 1) ' change the size of the array

        Dim counter As Integer
        For counter = 0 To b
            x(counter) = ListBox1.Items(counter)
            If (Val(x(counter)) = TotalN) Then
                sum = (sum + x(counter)) / TotalN
            End If
        Next
    End Sub
End Class

在Visual Basic中找到求和，平均，方差的问题

1 个答案: