Escape and unescape invalid characters

Question

This should be really easy. I have a string that i escape like the following:

string originalString = "M&M";
string escapedString = System.Security.SecurityElement.Escape(originalString);//M&M

Good so far

string unEscapedString = System.Security.SecurityElement.FromString(escapedString).Text;

Expecting to go back to M&M but getting "object not set"

Assuming string should be in xml format so any help on what i should do in this case would be helpful.

Answer 1

You can use System.Net.WebUtility class's static HtmlDecode method to do this:

string original = "M&M";
string escaped = System.Security.SecurityElement.Escape(original);
string unescaped = System.Net.WebUtility.HtmlDecode(escaped);

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The reason the code isn't working as you have it is because the FromString method expects valid xml. See the documentation here:

Parameters
xml String
The XML-encoded string from which to create the security element.

You can make your code sample work if you add xml tags around the string:

string unescaped = SecurityElement.FromString($"<x>{escaped}</x>").Text;