How to handle Regex with multiple patterns?

Question

I have a requirement where I need to read a query from access db and modify the query to replace all the keywords in the query to SQL executable query.. For eg: say there is a query 'Select key from table1"

here "key" is a reserved keyword.which has to be modified as "Select [key] from table1" (which will work in sql).

there is a possibility that the query can have multiple keywords..so I have a regex as below.

string pattern = "Key|IN|ON|VIEW]";
Regex rgx = new Regex(pattern);

I have the below code..which checks for the patterns..

string pattern = "Key|IN|ON|VIEW]";
Regex rgx = new Regex(pattern);  
string strModifiedQuery = string.Empty;
strModifiedQuery = strQueryText;
foreach (Match m in rgx.Matches(pattern))
{
    Console.WriteLine(m.Value);
    if (m.Value == "Key")
    {
        strModifiedQuery = rgx.Replace(strModifiedQuery, "[Key]");
    }

    if (m.Value == "IN")
    {
        strModifiedQuery = rgx.Replace(strModifiedQuery, "[IN]");
    }

    if (m.Value == "ON")
    {
        strModifiedQuery = rgx.Replace(strModifiedQuery, "[IN]");
    }

Is there a better way in c# to replace the matched pattern with a proper value?

Key|IN|ON|VIEW] wrong pattern...

Avinash Raj
– Avinash Raj

2014-08-27 09:18:20 +00:00
Commented Aug 27, 2014 at 9:18 — Avinash Raj
– Avinash Raj, Commented Aug 27, 2014 at 9:18

Sriram Sakthivel · Accepted Answer · 2014-08-27 09:26:12Z

2

var pattern = @"(?i)Key|IN|ON|VIEW";
var subject = "Select key from table1";
var result = Regex.Replace(subject, pattern, @"[$0]");

Produces

Select [key] from table1

(?i) turns on ignore case and replace pattern [$0] replaces whatever matched surrounded by brackets.

edited Aug 27, 2014 at 9:26

answered Aug 27, 2014 at 9:20

Sriram Sakthivel

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2 Comments

Jayaraman Over a year ago

if the query contains "[Key]"..how to ignore that from matching..because if the query already has [Key], after replacement it becomes [[Key]].

Sriram Sakthivel Over a year ago

That's indeed another question, ask new question please.

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