从单独的线程和类访问WinForms控件

Question

I have a class named "tables", and a winform "Form1", on the form is a button called "table3". The code in the "tables" class runs in a separate thread and needs access to the button on the main form, this is what I have:

Form1.ActiveForm.BeginInvoke(
(Action)(() =>
{
    Form1.ActiveForm.Controls["table3"].Text = "test";
}));

I'm getting a null reference exception.. The name of the button is correct. there's some other problem and I'm not sure what it could be :/

Answer 1

Try this:

Invoke(new Action<object>((args) =>
{
    Form1.ActiveForm.Controls["table3"].Text = "test";
}));

Answer 2

If you're getting a NullReferenceException, then a reference is null. So either Form1.ActiveForm == null , or Form1.ActiveForm.Controls == null , or Form1.ActiveForm.Controls["table3"] == null .

I assume Form1 is the name of the class and ActiveForm is a static property.