C＃无法从另一个类更改窗体的组件

Question

Before I start, I'd like to say that I have looked for an answer for this over the internet for quite a while, and unable to come to a solution. I know how to solve this, but it doesn't want to work.

Here's what I know: Assuming that I have a label and another class, if I want to manipulate the label I need to create an instance of the form that has the label, call the method of the new class with the form, and then call the method from within the form class that changes the label. This is what I have.

This is from the form class

    private void button1_Click(object sender, EventArgs e)
    {
        Question steve = new Question(1, 1, "nothing", new string[] {});
        steve.Show(new Form1(), "I win");
    }

    public void ChangeLabel(string s)
    {
        this.lblTest.Text = s;
    }

And this is the Question class

    public void Show (Form1 f, string str)
    {
        f.ChangeLabel(str);
    }

Syntax-wise this is correct, and when running the debugger lblTest.Text did equal "I win", but there were no visual changes on the form.

PS I am in high school and still learning C#, so if I made any mistakes in my explanation or the code, please point them out. Also, disregard the Question constructor, it's useless right now.

Thanks

Answer 1

No ! you don't need to create new instance of the form.

You must pass the current instance using this keyword:

private void button1_Click(object sender, EventArgs e)
{
    Question steve = new Question(1, 1, "nothing", new string[] {});
    steve.Show(this, "I win");    //change it
}