vb.net - Adding multiple textboxes real time

Question

When I run my code, I am able to successfully input values into other textboxes, but it does not sum all of the values into a textbox (txttotalcount) in real-time. It stays as a blank textbox.

I've tried using the txttotalcount_TextChanged. All other sources I've read uses the Button_Click, but I would like for the arithmetic to happen in real-time (no need to click a button).

I defined my textboxes to add +1 increment on button press:

Private Sub btnPMN_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPMN.Click
    'Add +1 to PMN Textbox (txtPMN)

    txtPMN.Text = (Val(txtPMN.Text) + 1).ToString()
End Sub

Private Sub BtnBand_Click(sender As Object, e As EventArgs) Handles btnBand.Click
    'Add +1 to Band Textbox (txtBand)

    txtBand.Text = (Val(txtBand.Text) + 1).ToString()
End Sub

Then I tried taking those textbox values and adding it into a final textbox (txttotalcount):

Private Sub Txttotalcount_TextChanged(sender As Object, e As EventArgs) Handles txttotalcount.TextChanged
    'Adds all text boxes 
    txttotalcount.text = txtPMN.Text + txtBand.Text


End Sub

I would like to sum all textboxes into a final textbox called txttotalcount.text in real-time (no button clicks)

When I run my code, the txttotalcount stays blank although there are values in the other textboxes.

标签： vb.netmathtextboxreal-time

Answer 1

执行此操作的正确方法是验证两个输入，并且仅在用户完成输入两个有效输入时才执行求和，例如

Private Sub TextBoxes_Validating(sender As Object, e As ComponentModel.CancelEventArgs) Handles TextBox2.Validating,
                                                                                                TextBox1.Validating
    Dim source = DirectCast(sender, TextBox)

    If source.TextLength > 0 AndAlso Not Integer.TryParse(source.Text, Nothing) Then
        source.SelectAll()
        source.HideSelection = False

        MessageBox.Show("Please enter a valid integer")

        source.HideSelection = True

        'Don't let the control lose focus with invalid contents.
        e.Cancel = True
    End If
End Sub

Private Sub TextBoxes_Validated(sender As Object, e As EventArgs) Handles TextBox2.Validated,
                                                                          TextBox1.Validated
    If TextBox1.TextLength > 0 AndAlso TextBox2.TextLength > 0 Then
        Label1.Text = (CInt(TextBox1.Text) + CInt(TextBox2.Text)).ToString()
    End If
End Sub

请注意，算术不会在用户键入时发生，而是在他们离开控件时发生。无需单击 aButton但焦点必须离开TextBoxes. 如果您真的愿意，您可以在输入更改时同时进行验证和算术运算，但我并没有真正看到向用户显示他们不感兴趣的结果的意义。

Private Sub TextBoxes_TextChanged(sender As Object, e As EventArgs) Handles TextBox2.TextChanged,
                                                                            TextBox1.TextChanged
    Dim input1 As Integer
    Dim input2 As Integer

    If TextBox1.TextLength > 0 AndAlso
       TextBox2.TextLength > 0 AndAlso
       Integer.TryParse(TextBox1.Text, input1) AndAlso
       Integer.TryParse(TextBox2.Text, input2) Then
        Label1.Text = (input1 + input2).ToString()
    Else
        Label1.ResetText()
    End If
End Sub