[英]updating inactive form.text from a thread in c#
I'm trying to update form.text from a thread. 我正在尝试从线程更新form.text。 Basically thread need to update the form.text with the current time.
基本上线程需要用当前时间更新form.text。 my code looks like below
我的代码如下所示
UpdateText("My Monitor (Last Updated " + DateTime.Now.ToString("HH:mm:ss tt") + ")", Form1.ActiveForm);
and the method as below 以及如下方法
void UpdateText(String s, Control c)
{
if (c.InvokeRequired)
{
this.BeginInvoke(new MethodInvoker(() => UpdateText(s, c)));
}
else
{
c.Text = s;
}
}
As long as the main application window is active, code works. 只要主应用程序窗口处于活动状态,代码就起作用。 If the application becomes inactive, then I get the error "Object reference not set to an instance of an object"
如果应用程序变为非活动状态,则会出现错误“对象引用未设置为对象的实例”
You are calling Form1.ActiveForm
. 您正在调用
Form1.ActiveForm
。
ActiveForm : A Form that represents the currently active form, or null if there is no active form.
ActiveForm :表示当前活动表单的Form;如果没有活动表单,则为null。
If the Form
is inactive, naturally this would be null
. 如果
Form
是不活动的,则自然为null
。 Use a different reference to your form. 对您的表单使用其他引用。 If you are calling it from within the form, use
this
. 如果要从表单中调用它,请使用
this
。
Keep the reference of ActiveForm
in a private field, and use that field in the Thread
将
ActiveForm
的引用保留在私有字段中,并在Thread
使用该字段
Control activeControl;
private void start_new_thread()
{
active = Form1.ActiveForm;
// start work under thread
}
private void work_under_thread(object state)
{
//blocking works
// update here
UpdateText("My Monitor (Last Updated " + DateTime.Now.ToString("HH:mm:ss tt") + ")", activeControl);
}
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