Removing Dynamically created controls in Panel

Question

I have spent hours trying to understand what is the problem in my coding but without any much result. Hence thought of posting here for an explanation

In my UI design, I have first row of <<checkbox, textbox, textbox>> in this order. And depending on the number of rows of result returned, I will dynamically create the same number of rows of checkbox and textboxes.

However when I try to remove the redundant rows, leaving only row 1 intact, I noticed that only some controls are being removed.

For eg

Before deleted:

checkbox0 textbox0 tb0

checkbox1 textbox1 tb1

checkbox2 textbox2 tb2

After executing

checkbox0 textbox0 tb0

--------- -------- tb1

checkbox2 textbox2 ---

My code for removing is as below:

foreach (Control c in panel1.Controls)
{                
  lastChar = c.Name[c.Name.Length - 1];
  lastValue = (int)Char.GetNumericValue(lastChar);
  MessageBox.Show("second " + c.Name);

  if (lastValue > 0 && lastValue < count)
  {
    panel1.Controls.Remove(c);
    c.Dispose();
  }
 }

Rightfully foreach will run through all the controls within the panel1. But i noticed that once the Remove statement is in, the whole operation went haywire.

Answer 1

You can not add or remove items into/from a IEnumerable inside a foreach loop. Instead try using a for loop. Check this . Actually the exception you are receiving should be telling you this.

for (int i = 0; i < panel1.Controls.Count; i++)
{                
  Control c = panel1.Controls[i];
  lastChar = c.Name[c.Name.Length - 1];
  lastValue = (int)Char.GetNumericValue(lastChar);
  MessageBox.Show("second " + c.Name);

  if (lastValue > 0 && lastValue < count)
  {
    panel1.Controls.Remove(c);
    c.Dispose();
    i--;
  }
 }

Answer 2

You can shorten @Adi's code slightly with:

        for (int i = panel1.Controls.Count - 1; i >= 0; i--)
        {
            Control c = panel1.Controls[i];
            lastValue = (int)Char.GetNumericValue(c.Name, c.Name.Length - 1);
            if (lastValue > 0 && lastValue < count)
            {
                c.Dispose();
            }
        }

Note the overload of GetNumericValue() to directly get your desired character value, and you only need to dispose of the control as this will automatically remove it from the container.