LINQ Interview Question #95

How can LINQ queries be built dynamically?

Deferred Execution, Immediate Execution & Query Behavior Mid-Level Intermediate

Quick Interview Answer

Start with an IEnumerable<T> or IQueryable<T> variable and conditionally append operators. For more complex provider-based scenarios, expression trees can be constructed or combined to create dynamic predicates.

Detailed Explanation

The important point is to preserve IQueryable while building database-side conditions if translation by the provider is desired.

Code Example

IQueryable<Product> query = db.Products;

if (!string.IsNullOrWhiteSpace(search))
    query = query.Where(
        p => p.Name.Contains(search));

if (categoryId.HasValue)
    query = query.Where(
        p => p.CategoryId == categoryId);

return await query.ToListAsync();