C# Regex Issue "unrecognized escape sequence"

I have an issue with the regular expressions I'm using but don't know how to continue with them. I get the error "unrecognized escape sequence".

I am trying to list out all files that could have a phone number in the formats listed in the code below

static void Main(string[] args)

    {
        //string pattern1 = "xxx-xxx-xxxx";
        //string pattern2 = "xxx.xxx.xxxx";
        //string pattern3 = "(xxx) xxx-xxxx";

        string[] fileEntries = Directory.GetFiles(@"C:\BTISTestDir");

        foreach (string filename in fileEntries)
        {
            StreamReader reader = new StreamReader(filename);
            string content = reader.ReadToEnd();
            reader.Close();

            string regexPattern1 = "^(\d{3开发者_C百科}\.){2}\d{4}$";
            string regexPattern2 = "^((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}$";

            if(Regex.IsMatch(content, regexPattern1))
                Console.WriteLine("File found: " + filename);
            if(Regex.IsMatch(content, regexPattern2))
                Console.WriteLine("File found: " + filename);
        }

        Console.WriteLine(Environment.NewLine + "Finished");
        Console.ReadLine();
    }

Any help is much appreciated.

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Use @ to make the strings no longer use the escape character \:

string regexPattern1 = @"^(\d{3}\.){2}\d{4}$";
string regexPattern2 = @"^((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}$";

As a side note, I think you want the two ifs at the end to be a single if with an or (||) between the two conditions.

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Add an additional '\' to unescape the escape. When it's processed it will then be interpreted in the manner you intended.

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The problem is not the regex, but the string. Before compiling it to a regex with the call to IsMatch(), the text you enter is still a normal string and it must obey the language rules.

\d in your language is not a recognized escape sequence, hence the error. You can either double backslashes (\ is the escape sequence to get a ) or, as Blindy pointed out, you can prefix your constant strings with a @, telling the compiler that it should not try to interpret anything looking like an escape sequence to it.