Specifies that no options are set.

Specifies case-insensitive matching.

Multiline mode. Changes the meaning of ^ and $ so they match at the beginning and end, respectively, of any line, and not just the beginning and end of the entire string.

Specifies that the only valid captures are explicitly named or numbered groups of the form. This allows unnamed parentheses to act as noncapturing groups without the syntactic clumsiness of the expression (?:…).

Specifies that the regular expression is compiled to an assembly. This yields faster execution but increases startup time.

Specifies single-line mode. Changes the meaning of the dot (.) so it matches every character (instead of every character except \n).

Eliminates unescaped white space from the pattern and enables comments marked with #. However, the System.Text.RegularExpressions.RegexOptions.IgnorePatternWhitespace value does not affect or eliminate white space in character classes.

Specifies that the search will be from right to left instead of from left to right.

Enables ECMAScript-compliant behavior for the expression. This value can be used only in conjunction with the System.Text.RegularExpressions.RegexOptions.IgnoreCase, System.Text.RegularExpressions.RegexOptions.Multiline, and System.Text.RegularExpressions.RegexOptions.Compiled values. The use of this value with any other values results in an exception.

Specifies that cultural differences in language is ignored. for more information.