When will you use this?

Use this lesson to build something you can demo — a sales dashboard or product search API.

• ShopNest.Analytics capstone proves you can filter, join, group, and paginate like a production reporting system.
• One complete analytics project on your resume beats reading fifty isolated LINQ operators.

Real-world: Flipkart-style marketplace

Real product: Flipkart-style marketplace (E-commerce). sellers and shoppers rely on product search and order reports every day. On this product, developers use Product Search Engine with LINQ to build Flipkart-style search with filters and paging. Without it, the team would write longer loops, ship slower features, or pull too much data from SQL Server. The example below is simplified on purpose — production code adds error handling, logging, and tests around the same LINQ pattern.

Production-style code

[HttpGet("api/products/search")]
public async Task<ActionResult<PagedResult<ProductListDto>>> Search(
    [FromQuery] ProductSearchQuery query, CancellationToken ct)
{
    var q = _context.Products.AsNoTracking().Where(p => p.IsPublished);

    if (!string.IsNullOrWhiteSpace(query.Q))
        q = q.Where(p => p.Name.Contains(query.Q) || p.Sku.Contains(query.Q));
    if (query.CategoryId is int cat)
        q = q.Where(p => p.CategoryId == cat);
    if (query.MinPrice is decimal min)
        q = q.Where(p => p.Price >= min);
    if (query.MaxPrice is decimal max)
        q = q.Where(p => p.Price <= max);

    var total = await q.CountAsync(ct);
    var items = await q
        .OrderBy(p => p.Price)
        .Skip((query.Page - 1) * query.PageSize)
        .Take(query.PageSize)
        .Select(p => new ProductListDto { Id = p.Id, Name = p.Name, Price = p.Price })
        .ToListAsync(ct);

    return Ok(new PagedResult<ProductListDto> { Total = total, Items = items });
}

What happens in production: In Flipkart-style marketplace, getting Product Search Engine with LINQ right means sellers and shoppers see correct product search and order reports quickly. That is the difference between a tutorial snippet and software people trust with money and operations data.

Lesson example (start here)

Copy this smaller example first. Once it works, compare it with the real-world code above.

IQueryable<Product> q = products.AsQueryable();

if (!string.IsNullOrWhiteSpace(term))
    q = q.Where(p => p.Name.Contains(term, StringComparison.OrdinalIgnoreCase));
if (categoryId > 0)
    q = q.Where(p => p.CategoryId == categoryId);
if (maxPrice > 0)
    q = q.Where(p => p.Price <= maxPrice);

var page = q.OrderBy(p => p.Name)
    .Skip((pageNum - 1) * 20)
    .Take(20)
    .Select(p => new { p.Id, p.Name, p.Price })
    .ToList();

Line-by-line walkthrough

How it works (big picture)

• Start with base query (published products only).
• Add Where only when the user supplied a filter.
• CountAsync for total pages.
• Skip/Take for the current page.
• All translatable to SQL if using EF Core.

Do this on your computer

1. Build the in-memory version with a List first.
2. Add three optional filters and test each combination.
3. Move to Web API + EF Core with the same pipeline.
4. Call /api/products/search?Q=mouse&maxPrice=2000&page=1 from Swagger.
5. Read the real-world section and name which part of the app uses this topic.
6. Run the example in a console app or LINQPad and confirm the output.
7. Change one filter or sort in the example and predict the result before you run it.

Experiments — try changing this

• Change a filter value (price, date, name) and run again — see how results change.
• Remove one operator from the chain, run, and read the error or different output.
• Make the Where condition always false — confirm you get zero results.
• Switch OrderBy to OrderByDescending and confirm sort direction flips.

Remember

Search = base IQueryable + optional Where clauses + OrderBy + Skip/Take. Count and page are separate queries — both should filter the same way. Portfolio-ready feature for ShopNest.Analytics.

Common questions