Regular expression validation on multiline textbox

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ASP.NET

Using Multineline textbox & applied validation throgh code behind on multiline text box.

s1 = @"(\d+";
       s2 = @")*\d+";

       string regx = s1 + Functions.ToString(ConfigurationManager.AppSettings["BulkCaseSeparator"].ToString() + s2);

       Regex.Match("example", @".*\n", RegexOptions.Multiline);

       RegularExpressionValidator1.ValidationExpression = regx;

above code is use for apply validation. all validation are working fine passing input in multiline textbox like
1213,1415 it is working fine
but when pass input like
1415,1617,
1819,
1920,
1415 not working how apply changes in code so this regular expression working on next line also.