Verbatim String or Regex Pattern from Input

[=?Utf-8?B?QWFyb24=?=]

Hi,

I'm having a tricky problem where I want to accept a regular expression
pattern from user input but can't get teh escape characters to be prcoessed
correctly. If I take the same pattern and declare it in code with a
preceeding @ character it works fine.

To get the pattern to work from teh suer all \ have to be escaped, e.g.
instead of \d a user would have to enter \\d.

Is there anyway to convert a normal string to a verbatim string or some
other way to get a string treated as a verbatim string by Regex?

Regards,

Aaron

[=?Utf-8?B?QWFyb24=?=]

Re: Verbatim String or Regex Pattern from Input



"Jon Skeet [C# MVP]" wrote:

Aaron <Aaron@discussi ons.microsoft.c omwrote:

I'm having a tricky problem where I want to accept a regular expression
pattern from user input but can't get teh escape characters to be prcoessed
correctly. If I take the same pattern and declare it in code with a
preceeding @ character it works fine.

To get the pattern to work from teh suer all \ have to be escaped, e.g.
instead of \d a user would have to enter \\d.

Is there anyway to convert a normal string to a verbatim string or some
other way to get a string treated as a verbatim string by Regex?

>
"Verbatim string literal" is a strictly compile-time business - it's
only relevant in actual C# code.
>
Could you post a short but complete program which demonstrates the
problem?
>

An example of the problem would be:

1. Ask the user for some input to be used as a regular expression pattern:

Enter =\d+

2. Read it in and attempt to use it as a regex pattern.

string pattern = Console.Readlin e();
if(Regex.Match( "12", pattern).Succes s)
{
Console.WriteLi ne("match");
}
else
{
Console.WriteLi ne("no match");
}

The output will be: no match.

3. If the user enters \\d+ the output will be: match.

Regards,

Aaron

[Gilles Kohl [MVP]]

Re: Verbatim String or Regex Pattern from Input

On Tue, 1 Apr 2008 03:08:07 -0700, Aaron <Aaron@discussi ons.microsoft.c om>
wrote:

>Hi,
>
>I'm having a tricky problem where I want to accept a regular expression
>pattern from user input but can't get teh escape characters to be prcoessed
>correctly. If I take the same pattern and declare it in code with a
>preceeding @ character it works fine.
>
>To get the pattern to work from teh suer all \ have to be escaped, e.g.
>instead of \d a user would have to enter \\d.
>
>Is there anyway to convert a normal string to a verbatim string or some
>other way to get a string treated as a verbatim string by Regex?
>
>Regards,
>
>Aaron

Hmm, is Regex.Escape what you are looking for?

Regards,
Gilles.