[VB2008]一個TextBox的問題

[j76992001 (人緣有待等)]

Public Class Form1
    Dim x, y, z
    Dim sum As Integer

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As
 System.EventArgs) Handles Button3.Click
        If MsgBox("確定離開程式", MsgBoxStyle.YesNo + MsgBoxStyle.Question, "離開程式") = MsgBoxResult.Yes Then
            End
        End If
    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As
 System.EventArgs) Handles TextBox1.TextChanged
        x = Val(TextBox1.Text)
        If x < 0 Or x > 1000 Then
            MsgBox("數值輸入錯誤", , "警告")
            TextBox1.Text = Nothing
        End If
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
 System.EventArgs) Handles Button1.Click
        If x = Nothing Or x < 0 Or x>1000 Then
            MsgBox("還沒輸入喔", , "警告")
            TextBox1.Text = Nothing
        Else
            Label2.Text = Label2.Text + 1
            Label5.Text = Label5.Text + 1
            Label8.Text = Label8.Text + x
            TextBox1.Text = Nothing
        End If
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As
 System.EventArgs) Handles Button2.Click
        TextBox1.Text = Nothing
    End Sub
End Class

這是一個輸入數值然後執行累加的程式,在輸入數值的TextBox1_TextChanged事件中,

我設定條件必須輸入數值才能執行累加的動作,但是假設我輸入的是數值為"0",

卻還是進到例外的範圍內.我有試過把x = Nothing拿掉,這樣雖然可以讓0累加成功,

卻會發生不輸入數值也能執行累加的問題... 想請問一下有什麼辦法可以解決這樣的問題


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