C# Online Compiler | .NET Fiddle

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main()
    {
        List<Transaction> transactions = new List<Transaction>
		{
			// These transactions should trigger the suspicious activity for CustomerID 1
			new Transaction { TransactionID = 1, CustomerID = 1, Timestamp = DateTime.Now.AddDays(-2).AddHours(-1), Amount = 10500m, TransactionType = "Deposit" },
			new Transaction { TransactionID = 2, CustomerID = 1, Timestamp = DateTime.Now.AddDays(-2).AddHours(1), Amount = 11000m, TransactionType = "Deposit" },
			new Transaction { TransactionID = 3, CustomerID = 1, Timestamp = DateTime.Now.AddDays(-2).AddHours(2), Amount = 12000m, TransactionType = "Withdrawal" },
			// Other transactions not triggering the suspicious activity
			new Transaction { TransactionID = 4, CustomerID = 2, Timestamp = DateTime.Now.AddMonths(-2), Amount = 5000m, TransactionType = "Deposit" },
			new Transaction { TransactionID = 5, CustomerID = 2, Timestamp = DateTime.Now.AddDays(-15), Amount = 7000m, TransactionType = "Withdrawal" },
		};


        // Step 1: Calculate the total number and total amount of transactions for each type
        var transactionsByType = transactions
            .GroupBy(t => t.TransactionType)
            .Select(g => new
            {
                TransactionType = g.Key,
                TotalNumber = g.Count(),
                TotalAmount = g.Sum(t => t.Amount)
            })
            .ToList();

        // Step 2: Identify any unusual transaction patterns
        var thresholdAmount = 10000m;
        var highVolumeTransactions = transactions
            .Where(t => t.Amount > thresholdAmount)
            .GroupBy(t => t.CustomerID)
            .SelectMany(g => g
                .OrderBy(t => t.Timestamp)
                .Select((t, i) => new { Transaction = t, Index = i })
                .Where(t => t.Index >= 2 && (t.Transaction.Timestamp - g.ElementAt(t.Index - 2).Timestamp).TotalHours <= 24))
            .Select(t => t.Transaction)
            .ToList();

        var suspiciousCustomers = highVolumeTransactions
            .Select(t => t.CustomerID)
            .Distinct()
            .ToList();

        // Step 3: Analyze the frequency of such patterns for suspicious customers
        var lastMonth = DateTime.Now.AddMonths(-1);
        var patternFrequency = suspiciousCustomers
            .ToDictionary(
                customerId => customerId,
                customerId => transactions
                    .Where(t => t.CustomerID == customerId && t.Timestamp > lastMonth && t.Amount > thresholdAmount)
                    .Count()
            );

        // Output results
        Console.WriteLine("Suspicious Transactions Detected:");
        foreach (var customer in suspiciousCustomers)
        {
            Console.WriteLine($"CustomerID: {customer}, High-Volume Large Transactions in Last Month: {patternFrequency[customer]}");
        }
    }
}

public class Transaction
{
    public int TransactionID { get; set; }
    public int CustomerID { get; set; }
    public DateTime Timestamp { get; set; }
    public decimal Amount { get; set; }
    public string TransactionType { get; set; }
}

 
using System;
using System.Collections.Generic;
using System.Linq;
​
public class Program
{
    public static void Main()
    {
        List<Transaction> transactions = new List<Transaction>
        {
            // These transactions should trigger the suspicious activity for CustomerID 1
            new Transaction { TransactionID = 1, CustomerID = 1, Timestamp = DateTime.Now.AddDays(-2).AddHours(-1), Amount = 10500m, TransactionType = "Deposit" },
            new Transaction { TransactionID = 2, CustomerID = 1, Timestamp = DateTime.Now.AddDays(-2).AddHours(1), Amount = 11000m, TransactionType = "Deposit" },
            new Transaction { TransactionID = 3, CustomerID = 1, Timestamp = DateTime.Now.AddDays(-2).AddHours(2), Amount = 12000m, TransactionType = "Withdrawal" },
            // Other transactions not triggering the suspicious activity
            new Transaction { TransactionID = 4, CustomerID = 2, Timestamp = DateTime.Now.AddMonths(-2), Amount = 5000m, TransactionType = "Deposit" },
            new Transaction { TransactionID = 5, CustomerID = 2, Timestamp = DateTime.Now.AddDays(-15), Amount = 7000m, TransactionType = "Withdrawal" },
        };
​
​
        // Step 1: Calculate the total number and total amount of transactions for each type
        var transactionsByType = transactions
            .GroupBy(t => t.TransactionType)
            .Select(g => new

Cached Result

Not nullable False
Nullable