increment existing filename if exists

Question

UPDATE: I just got another solution here: https://stackoverflow.com/a/1078898/14311474

I'm having a little problem with incrementing the current existing file.

instead of incrementing the current count, the filename becomes like this.

outputFileName(1).mp4
outputFileName(1)(1).mp4
outputFileName(1)(1)(1).mp4

I want the filename become like this:

outputFileName(1).mp4
if exists:
outputFileName(2).mp4
if exists:
outputFileName(3).mp4

Here's my code:

private void OverWriteFile(string OutputFileName)
{
    bool r = false;
    if (!string.IsNullOrEmpty(OutputFileName)) {
        if (File.Exists(OutputFileName)) {
            var dr = MessageBox.Show($"The file '{finalOutputVideoFilePath}' already exists. Overwrite? else \nfile name will be incremented", "Overwriting",
                                    MessageBoxButtons.YesNo, MessageBoxIcon.Question);
            if (dr == DialogResult.No) { 
            
            OutputFileName.GetNextFileName();
            
            }
            else {
                File.Delete(OutputFileName);
            }
        }
    }
    return r;
}

public static string GetNextFileName(this string fileName)
{
    string extension = Path.GetExtension(fileName);
    string pathName = Path.GetDirectoryName(fileName);
    string fileNameOnly = Path.Combine(pathName, Path.GetFileNameWithoutExtension(fileName));
    int i = 1;
    while (File.Exists(fileName))
    {
        Interlocked.Increment(ref i);
        fileName = string.Format("{0}({1}){2}", fileNameOnly, i, extension);
    }
    return fileName;
}