How do get the first occurrence of a char in Substring

First occurence

String.IndexOf('.')

Last occurence

String.LastIndexOf('.')

file.IndexOf(".")

Should get you the first occurence of ".". Otherwise it will return -1 if not found.

Use IndexOf and LastIndexOf string methods to get index of first and last occurrence of "search" string. You may use System.IO.Path.GetExtension(), System.IO.Path.GetFileNameWithoutExtension(), and System.IO.Path.GetDirectoryName() methods to parse the path.

For instance,

string file = @"c:\csnet\info.sample.txt";
Console.WriteLine(System.IO.Path.GetDirectoryName(file));           //c:\csnet
Console.WriteLine(System.IO.Path.GetFileName(file));                //info.sample.txt
Console.WriteLine(System.IO.Path.GetFileNameWithoutExtension(file));//info.sample
Console.WriteLine(System.IO.Path.GetExtension(file));               //.txt

To answer your actual question - you can use string.IndexOf to get the first occurrence of a character. Note that you'll need to subtract this value from your LastIndexOf call, since Substring's second parameter is the number of characters to fetch, not a start and end index.

However... Instead of parsing the names, you can just use Path.GetFilenameWithoutExtension to get the filename directly.