在VB.net中使用多个Texas Box进行计算 [英] Calculations Using multiple Texas Boxes in VB.net

问题描述

我正在尝试使用texbox21.text - texbox60.text = output到Label1进行基础减法.数学和函数有效.

这适用于具有相同等式但具有不同texbox的多行，
简单的数学.但是，如果值是空白，则会出现异常错误.这是我的代码，请让我了解我所缺少的内容.

I am trying to do baic subtraction using texbox21.text - texbox60.text = output to Label1. The math and function works.

This is for multiple rows of the same kind of equation but with different texboxes,
Simple math. But if the values are blank I get an exception Error. Here is my code please enlighten me on what I am missing.

Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        Dim Net1 As Double
        Dim Net2 As Double
        Dim Loaded1 As Double
        Dim End1 As Double
        Loaded1 = Double.Parse(TextBox21.Text)
        End1 = Double.Parse(TextBox60.Text)
        Dim Loaded2 As Double
        Dim End2 As Double
        
        If TextBox21.Text And TextBox60.Text = False Then
            Net1 = False
        End If

        If TextBox21.Text And TextBox60.Text = True Then
            Loaded1 = Double.Parse(TextBox21.Text)
            End1 = Double.Parse(TextBox60.Text)
            Net1 = Loaded1 - End1
            Label2.Text = Net1.ToString
        End If
    End Sub

推荐答案

类似的方法应该起作用:

Something like this should work:

Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
    If TextBox1.Text = "" Or TextBox2.Text = "" Then
        Exit Sub
    End If

    Dim Net1 As Double
    Dim Net2 As Double

    If Double.TryParse(TextBox1.Text, Net1) And Double.TryParse(TextBox2.Text, Net2) Then
        Label2.Text = Net1 - Net2
    Else
        If Not Double.TryParse(TextBox1.Text, Net1) Then
            MessageBox.Show("Value in first textbox cannot be converted to a Double")
            Exit Sub
        Else
            MessageBox.Show("Value in second textbox cannot be converted to a Double")
            Exit Sub
        End If
    End If
End Sub

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