vb.net 检测文本框中的文本何时更改（键入时）
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Detecting when text in a textbox changes (while typing)
提问by John
The .TextChangedevent on a TextBoxfires only after the TextBoxloses focus. Is there a way to detect every character that is being typed while the user is typing it?
只有在失去焦点后才会触发.TextChangeda 上的事件。有没有办法在用户键入时检测正在键入的每个字符？TextBoxTextBox
I know the radio button has a similar event called CurrentCellDirtyStateChangedto detect when the button is clicked without having to wait for it to lose focus. I was trying to find something similar for a TextBox.
我知道单选按钮有一个类似的事件，CurrentCellDirtyStateChanged用于检测按钮何时被点击，而不必等待它失去焦点。我试图为 a 找到类似的东西TextBox。
回答by Olivier Jacot-Descombes
It is not true that the TextChangedevent is triggered only when the textbox loses the focus. This code
TextChanged仅当文本框失去焦点时才触发该事件是不正确的。这段代码
Private Sub TextBox1_TextChanged(ByVal sender As System.Object, _
ByVal e As System.EventArgs) _
Handles TextBox1.TextChanged
System.Diagnostics.Debug.WriteLine("TextBox1.Text = " & TextBox1.Text)
End Sub
Yields the following output (in the Output window) when typing "Hello":
键入“Hello”时产生以下输出（在“输出”窗口中）：
TextBox1.Text = H
TextBox1.Text = He
TextBox1.Text = Hel
TextBox1.Text = Hell
TextBox1.Text = Hello
TextBox1.Text = H
TextBox1.Text = He
TextBox1.Text = Hel
TextBox1.Text = Hell
TextBox1.Text = 你好
However, it will also fire when you delete characters, so if your intention is to filter characters use one of the key events.
但是，它也会在您删除字符时触发，因此如果您打算过滤字符，请使用关键事件之一。
