Use following Code
StreamReader sr = new StreamReader(@"d:simpleTabDelimeterFile.txt");
StreamWriter outputFile = new StreamWriter(@"d:out.txt");
string strline = "";
string[] _values = null;
while (!sr.EndOfStream)
{
strline = sr.ReadLine();
_values = strline.Split('t');
if( _values.Length == 3 )
{
strline = _values[0] + 't' + _values[1] + 't' + _values[2];
outputFile.WriteLine(strline);
}
}
sr.Close();
outputFile.Close();