当我尝试运行程序来计算付款和总利息时,我得到“从字符串转换”到类型“双”无效。
我究竟做错了什么?
Dim P As Double
Dim R As Double
Dim N As Double
Dim Payment As Double
Dim totalInterest As Double
Private Sub btnAnalyze_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAnalyze.Click
P = CDbl(txtAmount.Text)
N = CDbl(txtDuration.Text)
R = CDbl(txtInterestRate.Text)
Payment = (P * R) / (1 - (1 + R) ^ (-N))
totalInterest = (N * Payment) - P
Payment = CDbl(txtPayment.Text)
totalInterest = CDbl(txtInterest.Text)
If P < 0 Then
MessageBox.Show("Please enter in loan amount")
End If
If R <= 0 Then
MessageBox.Show("Please enter in loan amount")
End If
If N <= 0 Then
MessageBox.Show("Please enter in loan amount")
End If
End Sub
End Class