Regular Expression for validating Windows-based file paths including UNC paths - regex

Question

I wanted to validate a file name along with its full path. I tried certain Regular Expressions as below but none of them worked correctly.
^(?:[\w]\:|\\)(\\[a-z_\-\s0-9\.]+)+\.(txt|gif|pdf|doc|docx|xls|xlsx)$
and
^(([a-zA-Z]\:)|(\\))(\\{1}|((\\{1})[^\\]([^/:*?<>""|]*))+)$
etc...
My requirement is as mentioned below:
Lets say if the file name is "c:\Demo.txt" then it should check every possibilites like no double slash should be included(c:\\Demo\\demo.text) no extra colon like(c::\Demo\demo.text). Should accept UNC files like(\\staging\servers) and others validation as well. Please help. I am really stuck here.

Answer 1

Why are you not using the File class ?
Always use it !
File f = null;
string sPathToTest = "C:\Test.txt";
try{
f = new File(sPathToTest );
}catch(Exception e){
Console.WriteLine(string.Format("The file \"{0}\" is not a valid path, Error : {1}.", sPathToTest , e.Message);
}
MSDN : http://msdn.microsoft.com/en-gb/library/system.io.file%28v=vs.80%29.aspx
Maybe you're just looking for File.Exists ( http://msdn.microsoft.com/en-gb/library/system.io.file.exists%28v=vs.80%29.aspx )
Also take a look to the Path class ( http://msdn.microsoft.com/en-us/library/system.io.path.aspx )
The GetAbsolutePath could be one way to get what you want! ( http://msdn.microsoft.com/en-us/library/system.io.path.getfullpath.aspx )
string sPathToTest = "C:\Test.txt";
string sAbsolutePath = "";
try{
sAbsolutePath = Path.GetAbsolutePath(sPathToTest);
if(!string.IsNullOrEmpty(sAbsolutePath)){
Console.WriteLine("Path valid");
}else{
Console.WriteLine("Bad path");
}
}catch(Exception e){
Console.WriteLine(string.Format("The file \"{0}\" is not a valid path, Error : {1}.", sPathToTest , e.Message);
}

Answer 2

If you are interested only in the filename part (and not the whole path because you get the file via upload) then you could try something like this:
string uploadedName = #"XX:\dem<<-***\demo.txt";
int pos = uploadedName.LastIndexOf("\\");
if(pos > -1)
uploadedName = uploadedName.Substring(pos+1);
var c = Path.GetInvalidFileNameChars();
if(uploadedName.IndexOfAny(c) != -1)
Console.WriteLine("Invalid name");
else
Console.WriteLine("Acceptable name");
This will avoid the use of Exceptions as method to drive the logic of your code.