help with dynamic checkboxes

kainat saleem

hi....

i have written following code which displays dynamic check boxes for X and Y co-ordinates...

now, i need help in adding some logic and functionality in them...

i want that the user can check only 1 check box for each co-ordinate i.e 1 for X axis and 1 for Y axis...

also if user select same check boxes for both co-ordinates i.e checkbox 2 for X and also check box 2 for Y error message should be displayed...

i also want to get the index number of checked box as an integer...

as i am new to the language em not getting these things rite...

help is required...

thankyou in advance...

my code is....

------------------------------------------------------------------------------------------------------------------------------------------------------------------

public partial class Form1 : Form
    {
        CheckBox[] CB2;
           CheckBox[] CB;
           string[] names = new string[] { "sepal length", "sepal width", "petal length", "petal width" };
           int No_Columns;
           public Form1()
           {
               InitializeComponent();

               No_Columns=4;

           CB=new CheckBox[No_Columns];
               for (int i = 0; i < No_Columns; i++)
               {
                   CB[i] = new CheckBox();
                   CB[i].Left = 20;
                   CB[i].Top = (i + 1) * 30;
                   CB[i].Name = "CB" + i.ToString();
                   CB[i].Text = names[i];//"CB" + i.ToString();
                   CB[i].CheckedChanged += new EventHandler(CheckedChanged);
                  // this.Controls.Add(CB[i]);

               }


              CB2=new CheckBox[No_Columns];
               for (int i = 0; i < No_Columns; i++)
               {
                   CB2[i]= new CheckBox();
                   CB2[i].Left = 190;
                   CB2[i].Top = (i + 1) * 30;
                   CB2[i].Name = "CB2" + i.ToString();
                   CB2[i].Text = names[i];//"CB2" + i.ToString();
                   CB2[i].CheckedChanged += new EventHandler(CheckedChanged2);
                   //this.Controls.Add(CB2[i]);
               }
               for (int i = 0; i < No_Columns; i++) {
                   this.Controls.Add(CB[i]);
                   this.Controls.Add(CB2[i]);

               }

           }
-------------------------- Event HAndlers-------------------------------

private void CheckedChanged(object sender, EventArgs e)
           {
               CheckBox button = (CheckBox)sender;
               //System.Windows.Forms.MessageBox.Show(button.Text.ToString());
               for (int i = 0; i < No_Columns; i++)
               {
                   if ("CB" + i.ToString() == button.Text.ToString())
                   {

                   }
                   else
                   {
                       CB[i].Checked = false;
                   }
               }
           }
               private void CheckedChanged2(object sender, EventArgs e)
           {
               CheckBox button = (CheckBox)sender;
               //System.Windows.Forms.MessageBox.Show(button.Text.ToString());
               for (int i = 0; i < No_Columns; i++)
               {
                   if ("CB2" + i.ToString() == button.Text.ToString())
                   {


                   }
                   else
                   {
                       CB2[i].Checked = false;
                   }
               }
               //CheckBox button = (CheckBox)sender;
               //button.Checked = true;
           }

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes12y ago
Accepted answer
If there are 11 or more checkboxes, then you'll need to make the highlighted changes:

// add these fields
private bool reentry = false;
private bool reentry2 = false;

private void CheckedChanged(object sender, EventArgs e)
{
if (reentry)
{
reentry = false;
return;
}

CheckBox button = (CheckBox)sender;
int len = button.Name.Length;
int index;
if (len == 3)
index = button.Name[2] - 48; // ASCII value of '0' is 48
else
index = int.Parse(button.Name.Substring(2));
CheckBox restore = null;

// make sure only one checkbox checked for this axis

for (int i = 0; i < No_Columns; i++)
{
if (i == index) continue;
CheckBox cb = (CheckBox)this.Controls["CB" + i];
if (cb.Checked)
{
reentry = true;
restore = cb;
cb.Checked = false; // uncheck it
break;
}
}

// make sure that if a checkbox is checked for the other axis it doesn't have the same index

CheckBox cb2 = (CheckBox)this.Controls["CB2" + index];
if (cb2.Checked)
{
MessageBox.Show(names[index] + " already checked for Y-axis");
reentry = true;
button.Checked = false;
if (restore != null) // restore previously checked checkbox if there is one
{
reentry = true;
restore.Checked = true;
}
}
}

private void CheckedChanged2(object sender, EventArgs e)
{
if (reentry2)
{
reentry2 = false;
return;
}

CheckBox button = (CheckBox)sender;
int len = button.Name.Length;
int index;
if (len == 4)
index = button.Name[3] - 48; // ASCII value of '0' is 48
else
index = int.Parse(button.Name.Substring(3));
CheckBox restore = null;

// make sure only one checkbox checked for this axis

for (int i = 0; i < No_Columns; i++)
{
if (i == index) continue;
CheckBox cb2 = (CheckBox)this.Controls["CB2" + i];
if (cb2.Checked)
{
reentry2 = true;
restore = cb2;
cb2.Checked = false; // uncheck it
break;
}
}

// make sure that if a checkbox is checked for the other axis it doesn't have the same index

CheckBox cb = (CheckBox)this.Controls["CB" + index];
if (cb.Checked)
{
MessageBox.Show(names[index] + " already checked for X-axis");
reentry2 = true;
button.Checked = false;
if (restore != null) // restore previously checked checkbox if there is one
{
reentry2 = true;
restore.Checked = true;
}
}
}
kainat saleem12y ago
sorry to disturb you again... but what if checkboxes exceed to 11??? then the value does not lie between 0-9... how can i deal with that???
Vulpes12y ago
Well, we know that in this case the button.Name property will return a string which is 3 characters long and so button.Name[2] is the final character.

We also know that this character is a digit, '0' to '9', and so its ASCII (or Unicode) value will be between 48 and 57.

When you subtract an integer from a character, the latter is first converted to its unicode equivalent.

So, button.Name[2] - 48 will return an integer between 0 and 9. In other words we're converting the chars '0' to '9' into actual numbers :)
kainat saleem12y ago
do me one more favour.... plz xplain how this is working??? int index = button.Name[2] - 48;
kainat saleem12y ago
Vulpes12y ago
I assume there's some reason why you didn't want to use RadioButton groups instead of CheckBoxes as that would have automatically ensured that only one RadioButton could be checked within the group.

Anyway, try this code. It's not straightforward to program this because if you need to change a CheckBox's checked status because there's already another CheckBox checked on that axis or the corresponding CheckBox on the other axis is already checked, then it causes the CheckedChanged event to be immediately fired again! You therefore need to deal with the event handler being re-entered in this way:

// add these fields
private bool reentry = false;
private bool reentry2 = false;

private void CheckedChanged(object sender, EventArgs e)
{
if (reentry)
{
reentry = false;
return;
}

CheckBox button = (CheckBox)sender;
int index = button.Name[2] - 48; // ASCII value of '0' is 48
CheckBox restore = null;

// make sure only one checkbox checked for this axis

for (int i = 0; i < No_Columns; i++)
{
if (i == index) continue;
CheckBox cb = (CheckBox)this.Controls["CB" + i];
if (cb.Checked)
{
reentry = true;
restore = cb;
cb.Checked = false; // uncheck it
break;
}
}

// make sure that if a checkbox is checked for the other axis it doesn't have the same index

CheckBox cb2 = (CheckBox)this.Controls["CB2" + index];
if (cb2.Checked)
{
MessageBox.Show(names[index] + " already checked for Y-axis");
reentry = true;
button.Checked = false;
if (restore != null) // restore previously checked checkbox if there is one
{
reentry = true;
restore.Checked = true;
}
}
}

private void CheckedChanged2(object sender, EventArgs e)
{
if (reentry2)
{
reentry2 = false;
return;
}

CheckBox button = (CheckBox)sender;
int index = button.Name[3] - 48; // ASCII value of '0' is 48
CheckBox restore = null;

// make sure only one checkbox checked for this axis

for (int i = 0; i < No_Columns; i++)
{
if (i == index) continue;
CheckBox cb2 = (CheckBox)this.Controls["CB2" + i];
if (cb2.Checked)
{
reentry2 = true;
restore = cb2;
cb2.Checked = false; // uncheck it
break;
}
}

// make sure that if a checkbox is checked for the other axis it doesn't have the same index

CheckBox cb = (CheckBox)this.Controls["CB" + index];
if (cb.Checked)
{
MessageBox.Show(names[index] + " already checked for X-axis");
reentry2 = true;
button.Checked = false;
if (restore != null) // restore previously checked checkbox if there is one
{
reentry2 = true;
restore.Checked = true;
}
}
}