The problem is twofold: text files don't have "lines", and they certainly don't have "columns".
While that may seem wrong - and the File.ReadAllLines method would imply it is - it's actually true: textfiles have no intrinsic format, and "lines" are only accessible because the text file contains "end of line" characters which can be interpreted as separating lines. But you can't "replace a line", "insert a line", "delete a line", or "move to the last line" with a text file easily, because they don't have real "lines".
Similarly, nothing in a text file enforces columns, although it is possible to interpret "special characters" as column delimiters, they still have the same problems as lines do!
So to read the "last line" you need to read all the others first, and discard them.
The simplest way to do that is:
string[] lines = File.ReadAllLines(pathToFile);
if (lines.Length > 0)
{
string lastLine = lines[lines.Length - 1];
...
}
And then identify a "column separator" that is unique to yoru file - your data implies that ';' might be being used, but you will need to check properly to be sure. When you have the column separator character, you can break the last line into seperate "columns":
string[] lines = File.ReadAllLines(pathToFile);
if (lines.Length > 0)
{
string lastLine = lines[lines.Length - 1];
string[] columns = lastLine.Split(';');
if (columns.Length > 0)
{
string lastColumn = columns[columns.Length - 1];
...
}
}