Writting to a ListBox control from another class

[macgowan]

Hi ...

I have created a ListBox on a Form. I would like to write to the ListBox from other classes using a wrapper method in the Form Class.

I have a public method in the Form1 Class called WriteStatusMessage(). This method will format the string and add the date and time and in the future could write to a file.

I would like to be able to call this method from other classes. In the sample code below I an able to create an instance of the Form1 Class and then call the WriteStatusMessage() method. Stepping through the code I actaully get into the method and to the point where I do the Add() on the ListBox.Item Object.

Any idea why the message will not display on the ListBox? As you can see I have tryed the Update() and Invalidate() method, both to repaint the ListBox?

Thanks,
Chris

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace TestBlueRayon
{
    
    public class Form1 : System.Windows.Forms.Form
    {

            
        private void menuItemVideo_Click(object sender, System.EventArgs e)
        {
            //string strTemp; 
            string strMessage; 

            // Tell the user what is happening
            strMessage = "Create Video Object"; 
            WriteStatusMessage(strMessage);

            // Create the Video object
            Video GreenVideo = new Video();

            // Change the contrast
            // This call will try to write to the ListBox
            GreenVideo.SetVideoContrast(); 
        }




        public void WriteStatusMessage(string strMessage)
        {
            string strDisplayMessage; 

            DateTime dtCurrent = DateTime.Now;

            int nYear        = dtCurrent.Year;
            int nMonth       = dtCurrent.Month;
            int nDay         = dtCurrent.Day;
            int nHour        = dtCurrent.Hour;
            int nMinute      = dtCurrent.Minute;
            int nSecond      = dtCurrent.Second;
            int nMillisecond = dtCurrent.Millisecond;


            string strTemp; 

            strDisplayMessage = String.Format("{0,0:D4}.{1,0:D2}.{2,0:D2} {3,0:D2}:{4,0:D2}:{5,0:D2}.{6,0:D3}  {7}",
                                              nYear, 
                                              nMonth, 
                                              nDay, 
                                              nHour,
                                              nMinute,
                                              nSecond,
                                              nMillisecond,
                                              strMessage); 

            // Shutdown the painting of the ListBox as items are added.
            this.ListBoxStatus.BeginUpdate();
            this.ListBoxStatus.Items.Add(strDisplayMessage);
            this.ListBoxStatus.EndUpdate();

            // this.ListBoxStatus.Invalidate();
            this.ListBoxStatus.Update();

        }
    }
}



namespace TestBlueRayon
{
        public class Video
        {
                public Video()
                {
                     // This will not write to the ListBox ??             
                     Form1 NewForm = new Form1();
                     NewForm.WriteStatusMessage("Hello"); 
                }

        // Public attributes 
        public int nColor;
        public int nHue;
        public string strComment;



        public void SetVideoContrast(int nIndex)
        {
 
            // This will NOT write to the ListBox       
            Form1 NewForm = new Form1();
            NewForm.WriteStatusMessage("Hello"); 
            
            nColor = 12;
            nHue = 34;
            strComment = "Contrast has been set";
            
            
        }

        }
}

[fozzwald]

In your code examples, the Video code is instantiating a Form1 but not Showing it. Was that just meant to simplify your explanation? How are you binding the existing Form1 to the call in Video?

I reused your code and added another class from which main() was called...

public class AnotherClass
{
	public void Write(string s, Form1 f) 
	{
		f.WriteStatusMessage( s );
	}
	
	[STAThread]
	static void Main() 
	{
		Form1 form = new Form1();
		form.Show();
		AnotherClass a = new AnotherClass();
		a.Write( "Write Successful",form);
		MessageBox.Show(" Look at Form1 to see if it worked.");
	}
}

Looked ok to me.

[Andy Tacker]

check this out!

namespace TestBlueRayon
{
    
    public class Form1 : System.Windows.Forms.Form
    {
        private void menuItemVideo_Click(object sender, System.EventArgs e)
        {
            // Create the Video object
            Video GreenVideo = new Video();
            GreenVideo.m_Parentform1 = this;

            // Change the contrast
            // This call will try to write to the ListBox
            GreenVideo.UpdateParentFormListBox(); 
        }
    }
        public class Video
        {
                public Form1 m_Parentform1;
                public Video()
                {
                }

                public void UpdateParentFormListBox()
                {
                     m_Parentform1.WriteStatusMessage("Hello"); 
                }
        }
}