Regular Expressions

string sql = @"database.schema.table
database.schema.[table]
database.[schema].table
[database].[schema].table
 
should all be transformed to:
 
[database].[schema].[table]
";
string pattern = @"(?:\[?(\w+)\]?)?\.\[?(\w+)\]?";
Func<Match, string> replace = m =>
    (m.Groups[1].Success ? "[" + m.Groups[1].Value + "]" : "") + ".[" + m.Groups[2].Value + "]";
Console.WriteLine("{0}", Regex.Replace(sql, pattern, m=>replace(m)));

string pattern = @"(?:\[?([\w\$]+)\]?)?\.\[?([\w\$]+)\]?";

...
string open = @"(?:\[\s*?)?";
string close = @"(?:\s*?\])?";
string ident = @"([\w\$]+)";
string prefix = @"(?:" + open + ident + close + @"\s*?)?";
string suffix = @"(?:" + open + ident + close + @")";
string pattern = prefix + @"\.\s*?" + suffix;
...

Andreas Gieriet wrote:

matches
 
delete my database
 
as well
as
 
delete database
 

string b = @"25[0-5]|2[0-4]\d|1?\d?\d"; // longest match first
string n = @"(?:"+b+@")";               // wrap into non captuering group
string w = @"(?:\*|"+b+@")";            // allow * and wrap into non captuering group
string d = @"\.";                       // separating dot
string ip = n+d+w+d+w+d+w;              // the whole ip = b.(*|b).(*|b).(*|b)

Peter_in_2780 wrote:

Inside the square brackets, the fullstop is not a wildcard.

string replaced = Regex.Replace(all, @"\\begin\{verbatimtab\}.*\\end\{verbatimtab\}", (Match m) => (m.Value), RegexOptions.Singleline);

string p = @"\\begin\{verbatimtab\}[\s\S]*?\\end\{verbatimtab\}";
Console.WriteLine("{0}", Regex.Match(str1, p).Success);

1. use [\s\S] to match any character, independent of singleline or multiline setting
2. use lazy match *? to allow multiple such groups to be matched individually