Writing to a file and handling duplicate entries

Writing to a file and handling duplicate entries

BACKGROUND:
1 Button 1 File That Needs To Be Written To 1 TextBox 1 NumericUpDown
So, in my application I need to write to a file that will contain several
lines. Input is taken from a TextBox and a NumericUpDown control and it
comprises a string of general format string.Format("{0}|{1}",
TextBoxInput, NumericUpDownInput);.
What I need help with is actually checking for duplicate entries before
adding a new line. Basically, if the user decides to enter something they
already had (to update it with more "times" of it), the program should
check whether the newly entered input matches one of the lines, and if it
does, the {1} parts should be added together and replace the original
value, while maintaining the {0} part.
MY APPROACH:
The way I tried to approach this is by creating a list of type string
called newFile and a for loop used to loop through the originalFile so as
to find if the new input matches the already entered one.
Then, two possible cases: a) if it does, just replace the numeric input
part and add it to the newFile, b) if it doesn't, just add it to the
newFile.
At the end, I make use of a StreamWriter so as to overwrite the
originalFile with the newFile.
Unfortunately, I'm having quite a bit of trouble as my approach generates
a blank file for whatever reason. If I was to just use the StreamWriter
part without taking duplicate entries into account, it actually works just
fine.
Oh, and one more thing; it would be neat if the program could also check
for whether the file exists in the first place so as to avoid exceptions.
I have managed this but I do not think it is the best way to go about it.
Help me please. Thank you in advance.
Below is the code for the button click event which basically updates/adds
to the file (this is the only code you need, after all):
private void btnAdd_Click(object sender, EventArgs e)
{
if (cardTitle == "" || cardTitle == "-")
MessageBox.Show("Correct any errors before trying to add a
card to your Resources.", "Error!", MessageBoxButtons.OK,
MessageBoxIcon.Error);
if (!File.Exists("CardResources.ygodc"))
using (File.Create("CardResources.ygodc")) { };
string[] originalFile = File.ReadAllLines("CardResources.ygodc");
List<string> newFile = new List<string>();
for (int count = 0; count < originalFile.Length; count++)
{
string[] split = originalFile[count].Split('|');
string title = split[0];
string times = split[1];
if (title == cardTitle)
newFile[count].Replace(string.Format("{0}|{1}", title,
times), string.Format("{0}|{1}", title,
(nudTimes.Value + int.Parse(times)).ToString()));
else
newFile.Add(string.Format("{0}|{1}", cardTitle,
nudTimes.Value.ToString()));
}
using (StreamWriter sw = new
StreamWriter("CardResources.ygodc", true))
{
foreach (string line in newFile)
{
sw.WriteLine(line);
}
}
}
P.S: Sorry if I don't come out as clear enough, I'm not a native English
speaker.
EDIT: If you're wondering what cardTitle stands for, it's basically the
input from the TextBox.