.net - Visual Studio : Enable/Disable Button Through TextBox

Question

我想做的是，当其中一个文本框为空时，按钮被禁用，但是一旦两个文本框都填满，它就会启用按钮。我做错了什么？提前谢谢你!

Public Class ModifiedLoanCalculatorFRM
Private Sub calculateBTN_Click(sender As Object, e As EventArgs) Handles calculateBTN.Click
    If mortgageAmountTBX.Text.Equals("") Or interestRateTBX.Text.Equals("") Then
        calculateBTN.Enabled = False
    Else
        calculateBTN.Enabled = True
    End If

Answer 1

您将代码用于测试文本框的内容，然后将按钮的启用状态设置到按钮单击处理程序中。这意味着它只会在单击按钮时触发，如果它被禁用，则无法将其恢复。

如果您的意图是根据任一文本框是否为空来动态启用或禁用按钮，您可以将代码从按钮单击处理程序移到它自己的子例程中，然后创建“已更改”事件在您的两个文本框和表单的加载事件上，调用该子例程:

Private Sub setButtonState()
    If mortgageAmountTBX.Text.Equals("") Or interestRateTBX.Text.Equals("") Then
        calculateBTN.Enabled = False
    Else
        calculateBTN.Enabled = True
    End If
End Sub

Private Sub interestRateTBX_TextChanged(sender As Object, e As EventArgs) Handles interestRateTBX.TextChanged
    setButtonState()
End Sub

Private Sub mortgageAmountTBX_TextChanged(sender As Object, e As EventArgs) Handles mortgageAmountTBX.TextChanged
    setButtonState()
End Sub

Private Sub ModifiedLoanCalculatorFRM_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    setButtonState()
End Sub