等待异步任务后重置变量

Question

I've got a windows forms app where the code for the form contains this:

public partial class Form1 : Form
{
    bool testBool;

    public Form1()
    {
        InitializeComponent();
    }

    private async void Form1_Load(object sender, EventArgs e)
    {
        try
        {
            await new Form1().Run();
        }
        catch (Exception ex)
        {
            MessageBox.Show("Error: " + ex.Message);
        }

        Console.WriteLine(testBool);
    }

    private async Task Run()
    {
        Console.WriteLine(testBool);
        testBool = true;
        Console.WriteLine(testBool);
    }
}

What I've noticed is that the result I get in the Console is

false
true
false

Where I would expect it to be

false
true
true

What is happening to testBool during this process? Is there a way I can preserve the value of this variable after Run() is complete?

Answer 1

testBool is a instance field, every Form1 will have a different ones. If you want them to share the same testBool field, mark it as static :

public partial class Form1 : Form
{
    static bool testBool;
}

static (C# Reference)

Use the static modifier to declare a static member, which belongs to the type itself rather than to a specific object . The static modifier can be used with classes, fields, methods, properties, operators, events, and constructors, but it cannot be used with indexers, destructors, or types other than classes. For more information, see Static Classes and Static Class Members (C# Programming Guide).

Answer 2

As mentioned in the comments to your question, you are accessing two different instances of your Form1 class.

You are instantiating a new Form1 and calling the Run method of that new object, which will print out false then true , then when it returns from that, it writes the original Form1 instances value of testBool which is still false .

You may want to define your class as static , or at least provide a public static field, or private static with a public static field accessor property or function.