How to locate and replace special characters in an XML file with Visual C# .NET

We can use the SecurityElement.Escape method to replace the invalid XML characters in a string with their valid XML equivalent. The following table shows the invalid XML characters and their respective replacements

Character Name	Entity Reference	Character Reference	Numeric Reference
Ampersand	&	&	&
Left angle bracket	<	<	<
Right angle bracket	>	>	>
Straight quotation mark	"	"	'
Apostrophe	'	'	"

Sample Usage of this Escape method.

//Usage
srtXML = SecurityElement.Escape(strXML);
  

For this you need to import System.Security namespace. Alternatively you can also use this simple replace method with all special characters in a single method like below

public string EscapeXml(string s)
{
    string toxml = s;
    if (!string.IsNullOrEmpty(toxml))
    {
        // replace special chars with entities
        toxml = toxml.Replace("&", "&");
        toxml = toxml.Replace("'", "'");
        toxml = toxml.Replace("\"", """);
        toxml = toxml.Replace(">", ">");
        toxml = toxml.Replace("<", "&lt;");
    }
    return toxml;
}
  

Hope this is useful!

How to Escape Special Characters in XML from C#

I have written a code which escape special characters in XML while posting an XML Request. Here is the sample code sample.

private string EscapeXMLillegalCharacters (string strValue)
{
    return strValue.Replace("&", "&amp;").Replace("'", "&apos;").Replace("\"", "&quot;").Replace("<", "&lt;").Replace(">", "&gt;");
}

Hope this is useful. Happy coding

What are the special characters in XML?

If you use XML with no DTD, then these five character entities are assumed to be pre declared, and you can use them without declaring them:

<
The less-than character (<) starts element markup (the first character of a start-tag or an end-tag).

&amp;
The ampersand character (&) starts entity markup (the first character of a character entity reference).

&gt;
The greater-than character (>) ends a start-tag or an end-tag.

&quot;
The double-quote character (") can be symbolized with this character entity reference when you need to embed a double-quote inside a string which is already double-quoted.

&apos;
The apostrophe or single-quote character (') can be symbolized with this character entity reference when you need to embed a single-quote or apostrophe inside a string which is already single-quoted.

If you are using a DTD then you must declare all the character entities you need to use (if any), including any of the five above that you plan on using (they cease to be pre declared if you use a DTD). If you are using a Schema, you must use the numeric form for all except the five above because Schemas have no way to make character entity declarations.