添加 2 个文本框的值以在其中一个中显示结果

Question

在我的表单上，我有 2 个名为“txtsurcharges.text”和“txttotal.text”的文本框

txttotal 从 mysql 表中检索一个值，但我想要发生的是，当我在 txtsurcharges 中输入一个值并在 txttotal 中显示结果时，这个值会被添加。

这是我的 txtsurcharges 代码：

txtsurcharges.Text = String.Format("£{0}", txtsurcharges.Text)

这是我的 txttotal 代码：

Private Sub cbxPaymentID_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbxPaymentID.SelectedIndexChanged
        Dim dss As New DataSet
        If (cbxPaymentID.SelectedIndex <> -1) Then
            Dim daa As New MySqlDataAdapter("SELECT * from payment_details WHERE PaymentID=@PID", _
            objconnection)
            daa.SelectCommand.Parameters.AddWithValue("@PID", Convert.ToInt32(cbxPaymentID.SelectedValue))
            daa.Fill(dss)
            txttotal.Text = dss.Tables(0).Rows(0)("ServicePayment").ToString()

        End If
    End Sub

这是我添加 2 个值的代码，但不起作用：

Private Sub txtsurcharges_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtsurcharges.TextChanged
        Dim c As Integer
        c = Val(txtsurcharges.Text) + Val(txttotal.Text)
        c = txttotal.Text
    End Sub

Answer 1

试试这个（更新后显示 ASPX 和 VB 代码，带有几个静态值进行测试）

aspx 代码

<asp:TextBox ID="txtsurcharges" runat="server" Text="£5" AutoPostBack="true"></asp:TextBox>
    <asp:TextBox ID="txttotal" runat="server" Text="£5"></asp:TextBox>

vb代码

Private Sub txtsurcharges_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtsurcharges.TextChanged 
    Dim c As Integer 
    c = CInt(txtsurcharges.Text) + CInt(txttotal.Text) 
    txttotal.Text = c
End Sub

如您所见，您将 c 设置为 = 附加费和总计的总和，然后您将 c 重置回总计。

如果我现在将 txtsurcharges 更改为 10，那么 txttotal 将更改为 15。

您当然需要确保只能在 txtsurcharges 中输入数字。