Label in winform access

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Label in winform access

Rajkumar Rao 100

Hi ,

@Karen Payne MVP ,had read a lot of code blocks from you in github but i am a new learner in c# and like to ask something very small . I have a form and a class. In the Form named as Form1, i have a label which i would like to access in separate class. so how do i do it. I have read that for this, i have to create a instance of the form but i want to save my application from creating un-necessary objects as my focus is on memory and performance. So, can you please suggest what alternative left for me. so Please also suggest the best approach in terms of memory and performance . I won't mind sharing an example from you .

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Karen Payne MVP 35,586 Volunteer Moderator

My recommendation is to not access a label on your form from a class, instead use an event that when invoke and listened to from the form makes a decision to alter the label e.g. change the label foreground color based on a logical decision.

Using an event as per above cost virtually nothing in regards to memory.

In the following project, I show how to use an event to update the foreground color of a label base on if a int value is odd or even.

Form code

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        Operations.ColorsChanged += Operations_ColorsChanged;
    }

    private void Operations_ColorsChanged(Color color)
    {
        label1.ForeColor = color;
    }

    private void UpdateValueButton_Click(object sender, EventArgs e)
    {
        Singleton.Instance.Value += 1;
        Operations.DoSomeWork();
        label2.Text = $@"Singleton value is {Singleton.Instance.Value}";
    }
}

See the rest of code in the following project.

In closing, avoid accessing the label from another class by setting Modifiers property from private to public or passing the label to a class and modify a property.

Rajkumar Rao 100 Reputation points

2023-10-15T14:16:06.6366667+00:00
@Karen Payne MVP , Two question only .

The singleton pattern : so if i want to make a single instance of form1 and use it across my whole application , is this what i have to add in form1.cs

public partial class Form1 : Form { private static readonly Lazy<Form1> lazyInstance = new Lazy<Form1>(() => new Form1()); public static Form1 Instance => lazyInstance.Value; public string Label1Value { get; set; }

Karen Payne MVP 35,586 Volunteer Moderator

There is no need to use a Singleton, I used one to show a dynamic example.

I updated the code sample with a simpler example which uses the same event with a different condition, check if today is a weekend or not.

In Operations.cs

public static void CheckDayOfWeek()
{
    ColorsChanged?.Invoke(DateTime.Now.IsWeekend() ?
        Color.Brown :
        Color.Yellow);
}

In the form, a button Click event

private void IsWeekendButton_Click(object sender, EventArgs e)
{
    Operations.CheckDayOfWeek();
}

And added the following class

internal static class DateOnlyExtensions
{
    public static bool IsWeekend(this DateTime self)
        => self.DayOfWeek is DayOfWeek.Sunday or DayOfWeek.Saturday;

    public static bool IsWeekDay(this DateTime self)
        => !self.IsWeekend();

}

Karen Payne MVP 35,586 Reputation points Volunteer Moderator

2023-10-15T15:50:07.9966667+00:00
In addition, the following completely violates what I presented which is to not create an instance of a form or a form's control and that consumes additional memory for the life of the application until the application closes if Form1 is the main form. If Form1 is not the main form that brings in other issues. So never create a Singleton class for a form.

private static readonly Lazy<Form1> lazyInstance = new Lazy<Form1>(() => new Form1())

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