错误“从字符串转换”&引用；输入'；双倍'；在VB.net中无效

我正在尝试编写计算双精度值，但出现了一个错误，即从字符串“”转换为类型“double”无效。

    Dim x As Integer = "8"
    Dim f As Integer = "100"
    Dim z As Double
    Dim r As Double
    Dim Nw As Double
    Dim W As Double
    Dim Was As Double
    Dim Nwas As Double
    Dim cost As Double
    Dim IBLP As Double
    Dim sale As Double
    Dim sale1 As Double
    Dim last As Double


    Nw = CDbl(txtnetwasage.Text)
    W = CDbl(txtweight.Text)
    Was = CDbl(txtwastage.Text)
    Nwas = CDbl(txtnetweight.Text)
    cost = CDbl(txtcost.Text)
    IBLP = CDbl(txtwastage.Text)
    sale = CDbl(txtsale.Text)
    sale1 = CDbl(txtvsale1.Text)
    last = Double.Parse(txtlast.Text)

    Nw = (W) * (Was)
    Nwas = (W) + (Nwas)
    cost = (IBLP) / (x) * (Nwas)
    z = (cost) / (f) * (sale)
    sale = (z) + (cost)
    r = (cost) / (f) * (sale1)
    last = (r) + (cost)

---

下面是Codexer在注释中建议的

Double.TryParse（）

示例：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim W As Double
    If Not Double.TryParse(txtweight.Text, W) Then
        MessageBox.Show("Value: " & txtweight.Text, "Invalid Weight")
        txtweight.Focus()
        txtweight.SelectAll()
        Exit Sub
    End If

    Dim Nwas As Double
    If Not Double.TryParse(txtnetweight.Text, W) Then
        MessageBox.Show("Value: " & txtnetweight.Text, "Invalid Net Weight")
        txtnetweight.Focus()
        txtnetweight.SelectAll()
        Exit Sub
    End If

    ' ... etc ...

    ' ... everything is good, perform your calculations ...

End Sub

---

将所有

CDbl

更改为

Double.TryParse（您的文本字段，变量）

。。。一个或多个文本字段不是双精度文本。您需要确保输入是有效的双精度输入，

TryParse

将有所帮助。在代码的第一行，添加“Option Strict On”（选项严格开启）。试图声明一个整数并为其分配一个字符串会导致灾难。