string str = "BH01803502625DUNCAN JOHNNY 03092010M362340313 ";
int startIndex = 0;
int endIndex = str.Length;
string leftString = string.Empty;
string rightString = string.Empty;
int johnIndex=str.IndexOf("JOHNNY");
if(str.Contains("JOHNNY"))
{
leftString = str.Substring(0,johnIndex);
rightString = str.Substring(johnIndex+6);
}
Console.WriteLine(leftString+","+rightString);
Console.ReadLine();