Static class that contains the FixFileName() function which will replace invalid file name characters.

PROMS/Volian.Base.Library/ValidFileName.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Volian.Base.Library
+{
+	// Part of fix for B2019-032 - will clean up the passed in file name.
+	public static class ValidFileName
+	{
+		/// <summary>
+		/// Replaces characters in orgTxt that are not allowed in file names with the specified replacement character.
+		/// </summary>
+		/// <remarks>
+		/// Note that Forward Slash, Back Slash and Pipe (vertical bar) are replaced with a dash '-'.
+		/// The Double quote is replaced with a single quote.
+		/// Everything else is replaced with a '_' unless a different replace char is passed in.
+		/// A null (zero) replacement character will cause the invalid characters to be removed.
+		/// The list of invalid characters include Double Quote, Less Than, Greater Than, Pipe, Question Mark, Back and Forward Slashes, Colin.
+		/// Also invalid are characters less than Ascii 32 (space) and greater than Ascii 126 (tilde)
+		/// </remarks>
+		/// <param name="orgTxt">Text to make into a valid filename. The same string is returned if it is valid already.</param>
+		/// <param name="replacementChar">Replacement character ('_' is the default), or null to simply remove bad characters.</param>
+		/// <param name="additionalInvalidChars">Character array of additional character to replace.</param>
+		/// <returns>A string that can be used as a filename. If the output string would otherwise be empty, returns "_".</returns>
+		public static string FixFileName(string orgTxt, char? replacementChar = '_', char[] additionalInvalidChars = null)
+		{
+			StringBuilder sb = new StringBuilder(orgTxt.Length);
+			bool changed = false;
+			//var invalidChars = System.IO.Path.GetInvalidFileNameChars();
+			char[] invalidChars = { '"', '<', '>', '|', '?', '\\', '/', ':' };
+			if (additionalInvalidChars != null) invalidChars = invalidChars.Union(additionalInvalidChars).ToArray();
+			for (int i = 0; i < orgTxt.Length; i++)
+			{
+				char c = orgTxt[i];
+				if (invalidChars.Contains(c) || !(c >= ' ' && c <= '~'))
+				{
+					changed = true;
+					var repl = replacementChar ?? '\0';
+					if (repl != '\0')
+					{
+						if (c == '\\' || c == '/' || c == '|')
+							sb.Append('-'); // replace forward slash, back slash, and vertical line (pipe) with a dash
+						else if (c == '"')
+							sb.Append('\''); // replace a double quote with a single quote
+						else
+							sb.Append(repl); // replace with '_' or passed in replacement character
+					}
+				}
+				else
+					sb.Append(c); // the character is OK just add it to the return string
+			}
+			if (sb.Length == 0)
+				return "_"; // return a '_' if return string is empty.
+			return changed ? sb.ToString() : orgTxt; // if we replaced a character return the corrected file name, else return the original file name
+		}
+	}
+}