Why does file.readalllines(filename) remove leading zeros when read from csv?

See more:

C#

Windows

I'm reading a CSV-File (5MB) with File.ReadAllLines(FileName). On my local system it works perfectly but on the customers system it removes the leading zeros of the line. There are no third party modules involved and I can't understand the behavior since it's plain string all the time.

private static string getCSVLine(string value, string[] _csvFileArray)
        {
            string csvLine = null;

            foreach (string line in _csvFileArray)
            {
                if (!line.StartsWith("#"))
                {
                    string[] csvLineSplit = line.Split(';');
                    if (value == csvLineSplit[0])
                    {
                        csvLine = line.Replace("\"", null);                   
                        return csvLine;
                    }
                }
            }
            return null;
        }

It's running as a service. The value in this method is correct and needs to match the first value of the line split. But all lines beginning with zeros are not being matched.

Example line of the CSV:

0000148542;234258;1000000010;"n";2003;"Cologne";"Name, Lastname";0;19461123

Edit: The title was misleading.. the leading zeros are being removed when held in a string array. The original csv file keeps untouched.

What I have tried:

Tested on my own system. Lines beginning with zeros are being read correctly. Differences between the two systems is that I'm working on Windows 7 and the customer runs the service at a Windows Server 2008 R2.