using System;

using System.Linq;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string error_message= "{\"2705\":\"Error importing username: 3167763, primary email: pkumar194@google.com, error: User already exists but Email does not match: pkumar194@googlee.com vs pkumar193@google.co.in\",\"10001\":\"Error importing username: 3195330, primary email: alejandra.mejia@google.com, error: User already exists but Email does not match: alejandra.mejia@google.com vs alejandra.mejia@googlee.com\"}";

        string pattern = @"Error importing username: (\d+), primary email: ([^,]+)";

        var dict = Regex.Matches(error_message, pattern)

            .Cast<Match>()

            .ToDictionary(match => match.Groups[1], match => match.Groups[2]);

        foreach (var kvp in dict) Console.WriteLine($"{kvp.Key}: {kvp.Value}");

    }

}

​

​