How to remove only one character c#

The TrimEnd method and other methods to remove the . work. But the issue may be reassigning the modified list of items to the ListBox.

The Items property of ListBox is a ReadOnly property, hence it can be used to retrieve the existing list of items, but it cannot be assigned back. Hence, the DataSource property can be used to set the modified list.

The TrimEnd('.') works but if there are spaces at the end then it will not work. So, it is better to use TrimEnd(new char[]{'.',' '}) to ensure that the . is removed even if there are trailing spaces. Since, it is required to remove only the . at the end of the string, I think it is a good option to use TrimEnd method.

The following code can be used to test the above points.

void Main()
{
    Form form1 = new Form();
    ListBox listBox1 = new ListBox();
    listBox1.Items.AddRange(new string[]{"my name","her name","your name.  "});
    form1.Controls.Add(listBox1);
    form1.ShowDialog();

    //Convert to ToList to set DataSource property of ListBox
    //Trim() is required to remove the extra space for the TrimEnd to work on .
    var items = listBox1.Items.Cast<string>().Select (s => s.TrimEnd(new char[]{'.',' '})).ToList();
   
    //This will not compile as Items  property is read only.
    //listBox1.Items = items;

    listBox1.DataSource=items;
    form1.ShowDialog();
}

s.Replace(".", "");

String.Replace('.','');

Just replace the . with an empty string.

At some point, you're adding items to the listbox:

ListBox lb;
String text;
String value;
.
.
.
lb.Items.Add(New ListItem(text, value);

To find and remove a period at the end of the text,

text = (text.Substring(text.length - 1, 1) == "."? text.substring(0, text.length - 1) : text);