Fixing / Removing Invalid Characters from a File Path / Name – c#

Below is a simple method for fixing bad filenames and paths. This uses the character lists from Path.GetInvalidPathChars and Path.GetInvalidFileNameChars (part of System.IO).

You should be able to pass a filename, directory or path. Example, calling these three lines would yield the below:

cleanPath(@"c:\tem|<p\fi<>le.txt")
cleanPath(@"c:\tem|<p\")
cleanPath(@"fi<le.txt")

Returns:

c:\tem-p\fi-le.txt
c:\tem-p\
fi-le.txt

You can also pass a string that’s used to replace the bad characters.

cleanPath(@"c:\tem|<p\fi<>le.txt", string.Empty)

Returns:

c:\temp\file.txt
 private string cleanPath(string toCleanPath, string replaceWith = "-")  
      {  
           //get just the filename - can't use Path.GetFileName since the path might be bad!  
           string[] pathParts = toCleanPath.Split(new char[] { '\\' });  
           string newFileName = pathParts[pathParts.Length - 1];  
           //get just the path  
           string newPath = toCleanPath.Substring(0, toCleanPath.Length - newFileName.Length);   
           //clean bad path chars  
           foreach (char badChar in Path.GetInvalidPathChars())  
           {  
                newPath = newPath.Replace(badChar.ToString(), replaceWith);  
           }  
           //clean bad filename chars  
           foreach (char badChar in Path.GetInvalidFileNameChars())  
           {  
                newFileName = newFileName.Replace(badChar.ToString(), replaceWith);  
           }  
           //remove duplicate "replaceWith" characters. ie: change "test-----file.txt" to "test-file.txt"  
           if (string.IsNullOrWhiteSpace(replaceWith) == false)  
           {  
                newPath = newPath.Replace(replaceWith.ToString() + replaceWith.ToString(), replaceWith.ToString());  
                newFileName = newFileName.Replace(replaceWith.ToString() + replaceWith.ToString(), replaceWith.ToString());  
           }  
           //return new, clean path:  
           return newPath + newFileName;  
      }  

Hope it helps!

Fixing / Removing Invalid Characters from a File Path / Name – c#

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