自動計算

Question

Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged, TextBox2.TextChanged 
If String.IsNullOrEmpty(TextBox1.Text) OrElse String.IsNullOrEmpty(TextBox2.Text) Then Exit Sub 
If Not IsNumeric(TextBox1.Text) OrElse Not IsNumeric(TextBox2.Text) Then Exit Sub 
TextBox3.Text = CDbl(TextBox1.Text) + CDbl(TextBox2.Text) 
End Sub 

此代碼適用於我，但是當我刪除兩個文本框的值總仍然存在...我的問題的任何解決方案？

Answer 1

當輸入TextBoxes（TextBox1和TextBox2）被清除時，沒有代碼可以從輸出TextBox（TextBox3）中刪除該值。您可以在TextChanged事件處理程序的開始處清除TextBox3。

Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged, TextBox2.TextChanged 
    TextBox3.Text = "" 
    If String.IsNullOrEmpty(TextBox1.Text) OrElse String.IsNullOrEmpty(TextBox2.Text) Then Exit Sub 
    If Not IsNumeric(TextBox1.Text) OrElse Not IsNumeric(TextBox2.Text) Then Exit Sub 
    TextBox3.Text = (CDbl(TextBox1.Text) + CDbl(TextBox2.Text)).ToString 
End Sub