自动计算

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 

此代码适用于我，但是当我删除两个文本框的值总仍然存在...我的问题的任何解决方案？

Answer 1

当输入TextBoxes（TextBox1和TextBox2）被清除时，没有代码可以从输出TextBox（TextBox3）中删除该值。您可以在TextChanged事件处理程序的开始处清除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