C＃中的Keypress事件 [英] Keypress event in C#

问题描述

我想在文本框中输入eky，它会在按键事件的标签上打印出来。

但是当我输入密钥时，它不会在标签上打印那个键那个时间。但是下次当我按下它显示标签中的文字。



例如当我在文本框中按2然后在标签中没有任何东西。

但是当我按23然后在标签2就在那里。



我尝试了什么：



private void txtdisount_KeyPress（object sender，KeyPressEventArgs e）

{

if（char.IsNumber（e.KeyChar）|| e .KeyChar =='。'）

{



lblDisVal.Text = txtdisount.Text;

< br $>


}



其他

{

e.Handled = e.KeyChar！=（char）Keys.Back;

}



}

解决方

尝试这种



<预郎= C＃> lblDisVal.Text = txtdisount.Text + e.KeyChar.ToString（）;

那是因为KeyPress事件发生在Text属性更新之前 - 如果没有，你将无法使用它阻止用户输入某些键！

使用TextChanged事件进行更新，使用Keypress进行过滤：

  private   void  txtdisount_KeyPress（ object  sender，KeyPressEventArgs e）
 {
  if （！char.IsNumber（e.KeyChar）&& e.KeyChar！=  ' 。'）
 {
 e.Handled = e.KeyChar！=（炭）Keys.Back; 
} 
} 
 
 私有  void  txtdisount_TextChanged（  object  sender，EventArgs e）
 {
 lblDisVal.Text = txtdisount.Text; 
} 

但是......你可能会更好地使用NumericUpDown控件！

i want to enter eky in textbox which will print it in label on keypress event.
but when i am entering key it is not printing that key in label that time.but next time when i am pressing it shows that text in label.

for e.g when i press "2" in textbox then in label nothing is there.
but when i press "23" then in label "2" is there.

What I have tried:

private void txtdisount_KeyPress(object sender, KeyPressEventArgs e)
{
if (char.IsNumber(e.KeyChar) || e.KeyChar == '.')
{

lblDisVal.Text = txtdisount.Text;


}

else
{
e.Handled = e.KeyChar != (char)Keys.Back;
}

}

解决方案

try this

lblDisVal.Text = txtdisount.Text + e.KeyChar.ToString();

That's because the KeyPress event occurs before the Text property is updated - if it didn't you wouldn't be able to use it to prevent some keys being entered by the user!
Use the TextChanged event to update, and Keypress to filter:

private void txtdisount_KeyPress(object sender, KeyPressEventArgs e)
    {
    if (!char.IsNumber(e.KeyChar) && e.KeyChar != '.')
        {
        e.Handled = e.KeyChar != (char)Keys.Back;
        }
    }

private void txtdisount_TextChanged(object sender, EventArgs e)
    {
    lblDisVal.Text = txtdisount.Text;
    }

But...you'd probably be better off using a NumericUpDown control instead!

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