Passing variable (time) from one form to another C#

Question

Let's say I have two forms. The first one will contain the start button and the other one is the stop button. Is there a way wherein I can determine the elapsed time between pressing the start and stop button and show it in the 2nd form.

I tried doing this and arrive at these codes

Form 1: Start button

namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
    public DateTime startTime2;
    public DateTime endTime;
    public TimeSpan ts_timeElapsed;
    public string s_timeElapsed;


    public Form1()
    {
        InitializeComponent();
    }

    private void StartButton_Click(object sender, EventArgs e)
    {
        startTime2 = DateTime.Now;
        Form2 frm = new Form2();
        frm.Show();
        this.Hide();


    }

    private void Button2_Click(object sender, EventArgs e)
    {
        Instructions frm = new Instructions();
        frm.Show();
        this.Hide();

    }


}
}

Form 2: Stop button

namespace WindowsFormsApplication1
{
public partial class RoadSign1Meaning : Form
{
    public DateTime startTime1;
    public DateTime endTime;
    public TimeSpan ts_timeElapsed;
    public string s_timeElapsed;

    public RoadSign1Meaning()
    {
        InitializeComponent();
    }
    public string GetElapsedTimeString()
    {
        int days = ts_timeElapsed.Days;
        int hours = ts_timeElapsed.Hours;
        int mins = ts_timeElapsed.Minutes;
        int secs = ts_timeElapsed.Seconds;
        string x = "";
        if (days != 0)
        {
            x += days.ToString() + ":";
        }
        if (hours != 0)
        {
            x += hours.ToString() + ":";
        }
        if (mins != 0)
        {
            x += mins.ToString() + ":";
        }
        if (secs != 0)
        {
            x += secs.ToString();
        }

        return x;
    }

    private void StopButton_Click(object sender, EventArgs e)
    {
                   endTime = DateTime.Now;
        ts_timeElapsed = (endTime - startTime1);
        s_timeElapsed = GetElapsedTimeString();
        ElapsedLabel.Text = "Time Elapsed: " + s_timeElapsed;

        Form3 frm = new Form3();
        frm.Show();
    }
}
}

However, the problem is the time value from form 1 is not save therefore form 2 display a wrong elapsed time value. Any suggestions to make my code work? Thanks!

Answer 1

It would be cleaner and more maintainable if stored the data in a place that is accessible from both forms. For example a static class. (You could also use a database or text file)

public static TempStore
{
    public DateTime StartTime { get; set; }
}

Set StartTime from From1 and read back the difference in Form2

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void StartButton_Click(object sender, EventArgs e)
    {
        TempStore.StartTime = DateTime.Now;

        // ...
    }
}

Form 2:

public partial class RoadSign1Meaning : Form
{
    public RoadSign1Meaning()
    {
        InitializeComponent();
    }

    private void StopButton_Click(object sender, EventArgs e)
    {
        TimeSpan span = DateTime.Now - TempStore.StartTime;             

        // ...
    }
}

This way, if you decide to pass more data to and from forms you can extend this static class.

Answer 2

Depending on if these forms exist within the same application, you could pass a reference to the first form into the second. And then (because the starttime1 DateTime object is public, you can access it from the second form.

Answer 3

Pass start time to second form

private void StartButton_Click(object sender, EventArgs e)
{
    Form2 frm = new Form2(DateTime.Now);
    frm.Show();
    this.Hide();
}

And then use it

public partial class Form2 : Form
{
    private DateTime startTime;

    public Form2(DateTime startTime)
    {
        InitializeComponent();
        this.startTime = startTime;
    }

    private void StopButton_Click(object sender, EventArgs e)
    {
        endTime = DateTime.Now;
        ts_timeElapsed = (endTime - startTime);
        s_timeElapsed = GetElapsedTimeString();
        ElapsedLabel.Text = "Time Elapsed: " + s_timeElapsed;

        Form3 frm = new Form3();
        frm.Show();
    }     
}

Answer 4

There are several solutions but also depends on the complexity of what would you like to achieve. The simplest one with less modifications in your code would be to declare a constructor on your second form which accepts a parameter of type DateTime and pass in startTime2 from Form1 when creating the Form2 just like Form2 form2 = new Form2(startTime2). A more elegant way would be to define an interface with a method GetElapsedTime() and create a concrete in which takes care of the start/end time and you can pass the concrete instance to Form2 like before from Form1.