Expense Tracker CLI with CSV Import/Export

Project roadmap

1. 01

   Create the project and Expense model

   ~1h

   Create a console project with dotnet new console and add CsvHelper with dotnet add package CsvHelper. Define an Expense record with Id, Amount (decimal, never double, for money), Category, Date (DateOnly) and Note. Done when: the project builds and runs.

2. 02

   Build the menu

   ~1.5h

   Write a menu loop offering: add an expense, list expenses, show the summary, import CSV, export CSV and quit. Listing shows expenses newest first in aligned columns, with amounts formatted to 2 decimals. Keep expenses in a List<Expense> for now. Done when: expenses can be added and listed from the menu.

3. 03

   Validate input

   ~1h

   When adding, parse the amount with decimal.TryParse (it must be greater than 0), and the date with DateOnly.TryParse (empty means today, and future dates are refused). The category can't be empty; offer the existing categories as suggestions. Ask again with a clear message on invalid input instead of crashing. Done when: typing letters for the amount or an invalid date re-asks the question.

4. 04

   Save to CSV

   ~1.5h

   Save all expenses to expenses.csv with CsvHelper after every change, using CultureInfo.InvariantCulture so decimals are always written with a dot. Load the file at startup, and start with an empty list when it doesn't exist. If the file is damaged, show which line is wrong instead of crashing. Done when: expenses are still there after restarting the app.

5. 05

   Show summaries with LINQ

   ~1.5h

   Use LINQ GroupBy to show the total per category (largest first, with each category's share of the total as a percentage) and the total per month (for example 2026-03), optionally filtered by a date range. Show the grand total at the end. Done when: the summary totals match the listed expenses.

6. 06

   Import and export

   ~1.5h

   Import expenses from another CSV file, mapping its columns with a CsvHelper ClassMap, skipping duplicates (same date, amount and note) and reporting how many were added and skipped. Export expenses for a chosen category or date range to a new CSV. Done when: importing the same file twice adds nothing the second time.

Resources

• DocsC# tutorials (Microsoft Learn)
• DocsCsvHelper documentation
• DocsLINQ: grouping data
• DocsRecords in C#