Why is this an issue?

Non-encoded control characters and whitespace characters are often injected in the source code because of a bad manipulation. They are either invisible or difficult to recognize, which can result in bugs when the string is not what the developer expects. If you actually need to use a control character use their encoded version:

• ASCII, for example \n and \t
• Unicode, for example U+000D and U+0009

This rule raises an issue when the following characters are seen in a string literal:

• ASCII control character. (character index < 32 or = 127)
• Unicode whitespace characters.
• Unicode C0 control characters
• Unicode characters U+200B, U+200C, U+200D, U+2060, U+FEFF, U+2028, U+2029

Exceptions

• Verbatim string literals and raw string literals, since they have no escape mechanism
• The simple space character: Unicode U+0020, ASCII 32

How to fix it

Code examples

Noncompliant code example

string tabInside = "A	B";                 // Noncompliant: contains a tabulation
string zeroWidthSpaceInside = "foo​bar";     // Noncompliant: contains a U+200B character inside
Console.WriteLine(zeroWidthSpaceInside);    // Prints "foo?bar"

Compliant solution

string tabInside = "A\tB";                      // Compliant: escaped value
string zeroWidthSpaceInside = "foo\u200Bbar";   // Compliant: escaped value
Console.WriteLine(zeroWidthSpaceInside);        // Prints "foo?bar"

Resources

Documentation

• Strings and string literals
• Control character