C# Good way to close a form.

Question

Say I want to open a new form..

TestForm test = new TestForm();

What is the good way to close it? More precisely, is only calling close() ok? Should I use the using() {} so dispose() is called ? And finally, suppose there is a dialog that should have only one instance of a dialog opened, is there a well "known" pattern? I've got different choices such as storing it in a static field, and null-"ing" it when it is closed..

Thanks

Answer 1

It is good practice to use using whenever the object implements IDisposable. This will work for a Modal dialog only:

using (TestForm test = new TestForm())
{
    ....
}

It's syntactically equivalent to a try{}finally{} block, so even if an exception is thrown inside the curly braces, Dispose() will be called on your object.

Answer 2

Don't stretch yourself to "using" that much. Close() is good enough unless you're creating and destroying hundreds of forms at once. GC will take care of it eventually.

Answer 3

Well in terms of your single instance dialog (if it's modal you don't have to worry) you can make the constructor private and provide a public static method to access the form.

public class MyForm : Form
{
    protected MyForm()
    {
    }

    protected int MyValue { get; set; }

    public static int GetResult()
    {
        using(MyForm myForm = new MyForm())
        {
            if(myForm.ShowDialog == DialogResult.OK)
                return myForm.MyValue;   
        }
        return -1;
    }
}

That would force calls to by in the form of..

int someValue = MyForm.GetResult();