在 c# winform 中更改的文本上启用禁用按钮
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Enable disable button on text changed in c# winform
提问by Gourav Goyal
I am developing an application, in which there is a button in search box (like one in itunes). I want to enable cancel button whenever there is text in text box and disable it when text box is empty. I tried with text_changed event on textbox with the following code, but it jump over the if condition. Even sender sends me correct values but i am unable to put it into if else.
我正在开发一个应用程序，其中搜索框中有一个按钮（就像 iTunes 中的一个）。我想在文本框中有文本时启用取消按钮，并在文本框为空时禁用它。我尝试使用以下代码在文本框上使用 text_changed 事件，但它跳过了 if 条件。即使发件人向我发送了正确的值，但我无法将其放入 if else 中。
private void textBox1_TextChanged(object sender, EventArgs e)
{
if (string.IsNullOrEmpty(sender.ToString()))
{
btn_cancel.Visible = false;
}
else
{
btn_cancel.Visible = true;
}
}
Please help
请帮忙
采纳答案by Inisheer
Here is a simple solution.
这是一个简单的解决方案。
private void textBox1_TextChanged(object sender, EventArgs e)
{
this.button1.Enabled = !string.IsNullOrWhiteSpace(this.textBox1.Text);
}
Of course, you'll have to set the button.Enabled = false when the form initially loads since the textbox event won't fire on startup (true for all answers currently provided for your question).
当然，您必须在表单最初加载时设置 button.Enabled = false，因为文本框事件不会在启动时触发（对于当前为您的问题提供的所有答案，均为 true）。
回答by sa_ddam213
Try this:
尝试这个：
private void textBox1_TextChanged(object sender, EventArgs e)
{
var textbox = sender as TextBox;
if (string.IsNullOrEmpty(textbox.Text))
{
btn_cancel.Visible = false;
}
else
{
btn_cancel.Visible = true;
}
}
sender.ToString()will always return System.Windows.Forms.TextBoxyou need to cast senderas TextBoxand use the Textvalue for your null or empty check
sender.ToString()将始终返回System.Windows.Forms.TextBox您需要转换sender为TextBox并使用Text您的空或空支票的值
回答by Afshin
try casting the sender to TextBox :
尝试将发件人强制转换为 TextBox ：
if (string.IsNullOrEmpty(((TextBox)sender).Text))
回答by Tommaso Belluzzo
private void textBox1_TextChanged(object sender, EventArgs e)
{
if (String.IsNullOrEmpty(textBox1.Text))
btn_cancel.Visible = false;
else
btn_cancel.Visible = true;
}
回答by Simon Whitehead
One liner:
一个班轮：
btn_cancel.Visible = textBox1.Text.Length > 0;
回答by Alex
This is how I'd do it:
这就是我要做的：
private void textBox1_TextChanged(object sender, EventArgs e)
{
string text = ((sender as TextBox) == null ? string.Empty : (sender as TextBox).Text);
this.button1.Enabled = (string.IsNullOrWhiteSpace(text) == false);
}
This doesn't assume the event source is a specific control and avoids an exception if by mistake it's attached to something that's not a TextBox.
这并不假设事件源是一个特定的控件，并且如果错误地将其附加到不是TextBox.
