How can I extract specific field values from a multiline string using regex in C#?

Below is an explanation of what’s happening and one way to fix the issue.

What’s Happening

In your code you are extracting values for Name, Age, and MobileNumber correctly because you assign the result to the variable “value” immediately after matching. However, for Billing address and Delivery address you are:

1. Not checking if the match succeeded (i.e. no if (match.Success) block).
2. Not updating the “value” variable with the extraction result.
3. Reusing the same variable “value” without assigning a new value in those two regex calls.

So even though you run new regex matches, you never assign a new value to “value.” This is why you keep printing the previously assigned value (or the value doesn’t change as expected).

How to Fix It

You need to:

• Check if the match is successful.
• Assign the matched group value to "value" for Billing address and Delivery address.
• Use a proper regex pattern for these cases.

For example, if your input string is conceptually written as:

Billing address                     Delivery address 
India                               India

You might want to capture the address on the next line rather than on the same line. One approach is to use a regex that looks for the label (e.g., "Billing address") then captures the next non-empty line.

Corrected Code Example

Below is one revised version of your code using separate regex patterns and proper assignments:

CSHARPCopied
using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        string strContent =
            @"[Name]
Jhon

[Age]
45

[MobileNumber]
1020304050

Billing address                     Delivery address 
India                               India";

        // Extract Name
        string value = string.Empty;
        var match = Regex.Match(strContent, @"\[Name\]\s*(.*)", RegexOptions.Multiline);
        if (match.Success)
        {
            value = match.Groups[1].Value.Trim();
        }
        Console.WriteLine("Name: " + value); //Jhon

        // Extract Age
        match = Regex.Match(strContent, @"\[Age\]\s*(.*)", RegexOptions.Multiline);
        if (match.Success)
        {
            value = match.Groups[1].Value.Trim();
        }
        Console.WriteLine("Age: " + value); //45

        // Extract MobileNumber
        match = Regex.Match(strContent, @"\[MobileNumber\]\s*(.*)", RegexOptions.Multiline);
        if (match.Success)
        {
            value = match.Groups[1].Value.Trim();
        }
        Console.WriteLine("MobileNumber: " + value); //1020304050

        // Extract Billing address
        // This regex looks for "Billing address" and then captures the following line that has the address.
        match = Regex.Match(strContent, @"Billing address\s*(?:\r?\n)+\s*(\S.*)", RegexOptions.Multiline);
        if (match.Success)
        {
            value = match.Groups[1].Value.Trim();
        }
        Console.WriteLine("Billing address: " + value); //India

        // Extract Delivery address
        match = Regex.Match(strContent, @"Delivery address\s*(?:\r?\n)+\s*(\S.*)", RegexOptions.Multiline);
        if (match.Success)
        {
            value = match.Groups[1].Value.Trim();
        }
        Console.WriteLine("Delivery address: " + value); //India

        Console.ReadLine();
    }
}

Explanation of the Changes

• Trim() Method: This ensures that any leading or trailing whitespace is removed.
• Regex for Addresses:
  • The pattern Billing address\s*(?:\r?\n)+\s*(\S.*) does the following:
    • Finds the text "Billing address"
    • Looks for one or more newline characters after it (using (?:\r?\n)+)
    • Captures the first non-whitespace character on the new line and the rest of that line ((\S.*))
• The same logic is applied for Delivery address.

This corrected code will now extract and print the correct values as expected.

Summary

Make sure to check for a successful regex match and update your variable accordingly for each field you want to extract. Adjusting the regex pattern to capture the value on the next line for addresses fixes the issue with incorrect values being used repeatedly.