Regex.Match 没有给出预期的结果

Question

I am using C# in Visual Studio 2017. I have below string

inputvalue = "
    OrderId:009
    Email:Ardi1234@yahoo.com
    ProductId:X206"

The below code should taken email address

var email =  Regex.Match(input: inputvalue, 
                     pattern: @"Email\:\ (.+)$", 
                     options: RegexOptions.Multiline).Groups[1].Value;

I want to get just email Address. but the result is an empty string. How can I do that?

Answer 1

Maybe, a bit over-engineered, yet it would extract the email address if there'd be any undesired spaces:

(?is)\bEmail:\s*([^@]+@[^.]+\.[a-z0-9]{2,6}(?:\.[a-z0-9]{2,6})?)$

Test

using System;
using System.Text.RegularExpressions;

public class Test
{
    public static void Main()
    {
        string pattern = @"(?is)\bEmail:\s*([^@]+@[^.]+\.[a-z0-9]{2,6}(?:\.[a-z0-9]{2,6})?)$";
        string input = @"OrderId:009
            Email:Ardi1234@yahoo.com
            ProductId:X206

            OrderId:009
                Email: Ardi1234@yahoo.co.uk
                ProductId:X206

            OrderId:009
                EMAIL: Ardi1234@yahoo.co.uk
                ProductId:X206";
        RegexOptions options = RegexOptions.Multiline;

        foreach (Match m in Regex.Matches(input, pattern, options))
        {
            Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
        }
    }
}

C# Demo

---

If you wish to simplify/modify/explore the expression, it's been explained on the top right panel of regex101.com . If you'd like, you can also watch in this link , how it would match against some sample inputs.

---

RegEx Circuit

jex.im visualizes regular expressions:

Answer 2

You can try: Email\:(.+) not clear if that input string as newline breaks though.

PS: pretty helpfull tool: https://www.regextester.com

Answer 3

The following seems to work:

var inputvalue = @"
OrderId:009
Email:Ardi1234@yahoo.com
ProductId:X206";

var email =  Regex.Match(input: inputvalue, 
                    pattern: @"Email:(.+)$", 
                    options: RegexOptions.Multiline).Groups[1].Value;
Console.WriteLine(email);

Ardi1234@yahoo.com

No regex

Regular expressions are awesome, but there is a way here without using them.

var inputvalue = @"
OrderId:009
Email:Ardi1234@yahoo.com
ProductId:X206";

var email = inputvalue.Split()
    .FirstOrDefault(l => l.StartsWith("email:", ignoreCase: true, culture: CultureInfo.InvariantCulture))
    ?.Replace("email:", "",ignoreCase: true, CultureInfo.InvariantCulture);

Console.WriteLine(email);

Output:

Ardi1234@yahoo.com

Answer 4

I've always preferred named capturing groups as they avoid filling code with magic numbers. The problem with the code though is that you have an extra space in the regex compared to the data you're hoping to match. There isn't any need to escape space, or colon here:

Regex.Match(input: inputvalue,
            pattern: @"Email:(?<eml>.+)$",
            options: RegexOptions.Multiline).Groups["eml"].Value;

I noted you have multiline set to true, so $ means "end of line" rather than "end of entire input" so the email address is correctly captured but it might well contain a trailing \r - watch out for this if it will be a problem

If your file will potentially have some spaces between the colon and the email address, consider this pattern:

Regex.Match(input: inputvalue,
            pattern: @"Email: *(?<eml>.+)$",
            options: RegexOptions.Multiline).Groups["eml"].Value;

This will match "zero or more spaces" between the colon and the email but they won't be captured into the email group

With no spaces, regex can match spaces:

With spaces, regex can match spaces:

With no spaces, regex cannot match spaces: