string - Getting out of range exception in Substring c#

Question

i am trying to print the Filename from last index of '//' till the file length.
file length is coming as 83 last index is coming as 47 then what wrong i am doing here

int idx = file.LastIndexOf('\');
int fl=   file.Length;
string filename = file.Substring(idx, fl);

Answer 1

Substring is not "from", "to" but "from", "length".

Starting at index 47 and 83 characters long is way out of the range of your current string.

If you want the rest of the string anyway, use

string filename = file.Substring(idx);

That said, C# has nice APIs for doing this. Use the Path class whenever possible and don't do this manually.