Trim String to int, then char to string, Listbox to textbox

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A format exception, according to the documentation means:

value does not consist of an optional sign followed by a sequence of digits (0 through 9).

Whatever you’re getting on this line:

string test = listBox2.SelectedItem.ToString().Trim();

Is not an parse-able integer. You should debug to figure out what the value is that you’re actually getting.

Hint: Trim does not grab the first character of the string. A quick google for some code examples on how to grab a substring or the first character of a string should find you what you need.

Once you’ve figured out getting the first character correctly, you can either wrap your code in a try-catch (example from the documentation):

try {
  result = Convert.ToInt32(value);
  Console.WriteLine("Converted the {0} value '{1}' to the {2} value {3}.",
                    value.GetType().Name, value, result.GetType().Name, result);
}
catch (OverflowException) {
   Console.WriteLine("{0} is outside the range of the Int32 type.", value);
}   
catch (FormatException) {
  Console.WriteLine("The {0} value '{1}' is not in a recognizable format.",
                     value.GetType().Name, value);
}

Or you can use TryParse and look at the boolean result to see if the parse completed successfully.

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