How to retain the value from an numericupdown after closing a form-CodePudding

I have the following question. I am using C# .NET, and I want to save a value in numericupdown box after I close my form. In my aplication I have in total 2 forms, so I want to save the value I enter in the second one, and after I open it again I want to see the last value. In my case the numericupdown value is empty after I open the second form again.

I was thinking about something like this:

namespace Project2
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            decimal a = numericUpDown1.Value;
            label2.Text = "N: "   a;
        }
    }
}

But is still empty after I open it again.

CodePudding user response：

You can use static variable to store last updated value and with the reference of class name you can use it where ever you want.

From MSDN: Two common uses of static fields are to keep a count of the number of objects that have been instantiated, or to store a value that must be shared among all instances.

Like,

namespace Project2
{
    public partial class Form2 : Form
    {
        public static decimal lastNumericUpDownValue = 0;  
        public Form2()
        {
            //For example: thiw will print lastest saved Numeric updown value.
            //For the first time, it will print 0
            Console.WriteLine(Form2.lastNumericUpDownValue);
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //Assign value to lastNumericUpDownValue variable. Look at how it is used.
            Form2.lastNumericUpDownValue = numericUpDown1.Value;
        }
    }
}

CodePudding user response：

You can create a class which provides set/get for a NumericUpDown control in this case using the following.

public sealed class Setting
{
    private static readonly Lazy<Setting> Lazy = 
        new Lazy<Setting>(() => new Setting());
    public static Setting Instance => Lazy.Value;
    public decimal NumericUpDownValue { get; set; }
}

In the child form, OnShown set Value property to Settings.NumericUpDownValue then OnClosing remember the value.

public partial class ChildForm : Form
{
    public ChildForm()
    {
        InitializeComponent();

        Shown  = (sender, args) => 
            numericUpDown1.DataBindings.Add("Value", Setting.Instance, 
                nameof(Setting.NumericUpDownValue));

        Closing  = (sender, args) => 
            Setting.Instance.NumericUpDownValue = numericUpDown1.Value;
    }
}

The code above, specifically Settings class is known as the Singleton Pattern which you can learn more about in Implementing the Singleton Pattern in C#.