J
Justin Lazanowski
I have a form that programmatticly creates 5 labels. Then programatticly
should dispose them, when this happens when it gets down to two lables left
it says that I get a null ref exception.. and I don't know why.
BTW if I check for null it leaves the two labels on my page
Can anyone explain this?
I have included the source code for this very simple test
<code>
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
namespace ControlProblem
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Button button1;
private System.Windows.Forms.Button button2;
private System.Windows.Forms.Panel panel1;
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null;
public Form1()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//
// TODO: Add any constructor code after InitializeComponent call
//
}
/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.button1 = new System.Windows.Forms.Button();
this.button2 = new System.Windows.Forms.Button();
this.panel1 = new System.Windows.Forms.Panel();
this.SuspendLayout();
//
// button1
//
this.button1.Location = new System.Drawing.Point(48, 296);
this.button1.Name = "button1";
this.button1.Size = new System.Drawing.Size(96, 23);
this.button1.TabIndex = 0;
this.button1.Text = "Create Controls";
this.button1.Click += new System.EventHandler(this.button1_Click);
//
// button2
//
this.button2.Location = new System.Drawing.Point(248, 296);
this.button2.Name = "button2";
this.button2.RightToLeft = System.Windows.Forms.RightToLeft.No;
this.button2.Size = new System.Drawing.Size(112, 23);
this.button2.TabIndex = 1;
this.button2.Text = "Dispose Controls";
this.button2.Click += new System.EventHandler(this.button2_Click);
//
// panel1
//
this.panel1.Location = new System.Drawing.Point(16, 16);
this.panel1.Name = "panel1";
this.panel1.Size = new System.Drawing.Size(368, 192);
this.panel1.TabIndex = 2;
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(392, 341);
this.Controls.Add(this.panel1);
this.Controls.Add(this.button2);
this.Controls.Add(this.button1);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
}
#endregion
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
private void createLabels()
{
int labelLoc = 0;
for(int i=0; i<5; i++)
{
labelLoc += 30;
Label lblDescriptor;
lblDescriptor = new Label();
lblDescriptor.ForeColor = Color.SaddleBrown;
lblDescriptor.Location = new System.Drawing.Point(10 , labelLoc);
lblDescriptor.TextAlign = System.Drawing.ContentAlignment.MiddleLeft;
lblDescriptor.Name = "lbl" + i.ToString();
lblDescriptor.Size = new System.Drawing.Size(100, 21);
lblDescriptor.Text = "Test Label 1 " + i.ToString();
this.panel1.Controls.Add(lblDescriptor);
}
}
private void button1_Click(object sender, System.EventArgs e)
{
createLabels();
}
private void button2_Click(object sender, System.EventArgs e)
{
foreach(Control c in this.panel1.Controls)
{
c.Dispose();
}
}
}
}
</code>
should dispose them, when this happens when it gets down to two lables left
it says that I get a null ref exception.. and I don't know why.
BTW if I check for null it leaves the two labels on my page
Can anyone explain this?
I have included the source code for this very simple test
<code>
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
namespace ControlProblem
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Button button1;
private System.Windows.Forms.Button button2;
private System.Windows.Forms.Panel panel1;
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null;
public Form1()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//
// TODO: Add any constructor code after InitializeComponent call
//
}
/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.button1 = new System.Windows.Forms.Button();
this.button2 = new System.Windows.Forms.Button();
this.panel1 = new System.Windows.Forms.Panel();
this.SuspendLayout();
//
// button1
//
this.button1.Location = new System.Drawing.Point(48, 296);
this.button1.Name = "button1";
this.button1.Size = new System.Drawing.Size(96, 23);
this.button1.TabIndex = 0;
this.button1.Text = "Create Controls";
this.button1.Click += new System.EventHandler(this.button1_Click);
//
// button2
//
this.button2.Location = new System.Drawing.Point(248, 296);
this.button2.Name = "button2";
this.button2.RightToLeft = System.Windows.Forms.RightToLeft.No;
this.button2.Size = new System.Drawing.Size(112, 23);
this.button2.TabIndex = 1;
this.button2.Text = "Dispose Controls";
this.button2.Click += new System.EventHandler(this.button2_Click);
//
// panel1
//
this.panel1.Location = new System.Drawing.Point(16, 16);
this.panel1.Name = "panel1";
this.panel1.Size = new System.Drawing.Size(368, 192);
this.panel1.TabIndex = 2;
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(392, 341);
this.Controls.Add(this.panel1);
this.Controls.Add(this.button2);
this.Controls.Add(this.button1);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
}
#endregion
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
private void createLabels()
{
int labelLoc = 0;
for(int i=0; i<5; i++)
{
labelLoc += 30;
Label lblDescriptor;
lblDescriptor = new Label();
lblDescriptor.ForeColor = Color.SaddleBrown;
lblDescriptor.Location = new System.Drawing.Point(10 , labelLoc);
lblDescriptor.TextAlign = System.Drawing.ContentAlignment.MiddleLeft;
lblDescriptor.Name = "lbl" + i.ToString();
lblDescriptor.Size = new System.Drawing.Size(100, 21);
lblDescriptor.Text = "Test Label 1 " + i.ToString();
this.panel1.Controls.Add(lblDescriptor);
}
}
private void button1_Click(object sender, System.EventArgs e)
{
createLabels();
}
private void button2_Click(object sender, System.EventArgs e)
{
foreach(Control c in this.panel1.Controls)
{
c.Dispose();
}
}
}
}
</code>