LINQ Operators And Lambda Expression - Syntax & Examples

Here is a list of code examples for LINQ operators and the equivalent Lambda Expressions.

LINQ Operators and Lambda Expressions

LINQ is a cool feature in C# 3.0. Most of the developers are struggling for the syntax and examples. Here I have collected various examples for each operator in LINQ and the equivalent Lambda Expressions.

Where

  1. IEnumerable<Product> x = products.Where(p => p.UnitPrice >= 10);  
  2.   
  3. IEnumerable<Product> x =  
  4. from p in products  
  5. where p.UnitPrice >= 10  
  6. select p;  

Select

  1. IEnumerable<string> productNames = products.Select(p => p.Name);  
  2. IEnumerable<string> productNames = from p in products select p.Name;  
  3.   
  4. var namesAndPrices =  
  5. products.  
  6. Where(p => p.UnitPrice >= 10).  
  7. Select(p => new { p.Name, p.UnitPrice }).  
  8. ToList();  
  9. IEnumerable<int> indices =  
  10. products.  
  11. Select((product, index) => new { product, index }).  
  12. Where(x => x.product.UnitPrice >= 10).  
  13. Select(x => x.index);  

SelectMany

  1. IEnumerable<Order> orders =  
  2. customers.  
  3. Where(c => c.Country == "Denmark").  
  4. SelectMany(c => c.Orders);  
  5. var namesAndOrderIDs =  
  6. customers.  
  7. Where(c => c.Country == "Denmark").  
  8. SelectMany(c => c.Orders).  
  9. Where(o => o.OrderDate.Year == 2005).  
  10. Select(o => new { o.Customer.Name, o.OrderID });  
  11. var namesAndOrderIDs =  
  12. customers.  
  13. Where(c => c.Country == "Denmark").  
  14. SelectMany(c => c.Orders, (c,o) => new { c, o }).  
  15. Where(co => co.o.OrderDate.Year == 2005).  
  16. Select(co => new { co.c.Name, co.o.OrderID });  
  17.   
  18. var namesAndOrderIDs =  
  19. from c in customers  
  20. where c.Country == "Denmark"  
  21. from o in c.Orders  
  22. where o.OrderDate.Year == 2005  
  23. select new { c.Name, o.OrderID };  

Take

  1. IEnumerable<Product> MostExpensive10 =products.OrderByDescending(p => p.UnitPrice).Take(10);  
Skip
  1. IEnumerable<Product> AllButMostExpensive10 = products.OrderByDescending(p => p.UnitPrice).Skip(10);  
TakeWhile SkipWhile
  1. s.TakeWhile(p) s.SkipWhile(p)   

Join

  1. var custOrders = customers.  
  2. Join(orders, c => c.CustomerID, o => o.CustomerID, (c, o) => new {  
  3.     c.Name, o.OrderDate, o.Total  
  4. });  
  5. var custOrders = from c in customers  
  6. join o in orders on c.CustomerID equals o.CustomerID  
  7. select new {  
  8.     c.Name, o.OrderDate, o.Total  
  9. };  
GroupJoin
  1. var custTotalOrders = customers.  
  2. GroupJoin(orders, c => c.CustomerID, o => o.CustomerID, (c, co) => new {  
  3.     c.Name, TotalOrders = co.Sum(o => o.Total)  
  4. });  
  5. var custTotalOrders = from c in customers  
  6. join o in orders on c.CustomerID equals o.CustomerID into co  
  7. select new {  
  8.     c.Name, TotalOrders = co.Sum(o => o.Total)  
  9. };  
  10. var custTotalOrders = from c in customers  
  11. join o in orders on c.CustomerID equals o.CustomerID  
  12. select new {  
  13.     c.Name, o.OrderDate, o.Total  
  14. };  
  15. var custTotalOrders = from c in customers  
  16. join o in orders on c.CustomerID equals o.CustomerID into co  
  17. from o in co  
  18. select new {  
  19.     c.Name, o.OrderDate, o.Total  
  20. };  
  21. var custTotalOrders = from c in customers  
  22. join o in orders on c.CustomerID equals o.CustomerID into co  
  23. from o in co.DefaultIfEmpty(emptyOrder)  
  24. select new {  
  25.     c.Name, o.OrderDate, o.Total  
  26. };   

Concat

  1. IEnumerable < string > locations = customers.Select(c => c.City).  
  2. Concat(customers.Select(c => c.Region)).  
  3. Concat(customers.Select(c => c.Country)).  
  4. Distinct();  
  5. IEnumerable < string > locations = new [] {  
  6.     customers.Select(c => c.City),  
  7.         customers.Select(c => c.Region),  
  8.         customers.Select(c => c.Country),  
  9. }.  
  10. SelectMany(s => s).  
  11. Distinct();  

OrderBy / ThenBy

  1. IEnumerable<Product> orderedProducts1 =  
  2. products.  
  3. OrderBy(p => p.Category).  
  4. ThenByDescending(p => p.UnitPrice).  
  5. ThenBy(p => p.Name);  
  6. IEnumerable<Product> orderedProducts1 =  
  7. from p in products  
  8. orderby p.Category, p.UnitPrice descending, p.Name  
  9. select p;  
  10. IEnumerable<Product> orderedProducts2 =  
  11. products.  
  12. Where(p => p.Category == "Beverages").  
  13. OrderBy(p => p.Name, StringComparer.CurrentCultureIgnoreCase);  
  14. IEnumerable<string> orderedProductNames =  
  15. products.  
  16. Where(p => p.Category == "Beverages").  
  17. Select(p => p.Name).  
  18. OrderBy(x => x);  
GroupBy
  1. IEnumerable<IGrouping<string, Product>> productsByCategory =products.GroupBy(p => p.Category);  
  2. IEnumerable<IGrouping<string, string>> productNamesByCategory =products.GroupBy(p => p.Category, p => p.Name);  
Distinct
  1. IEnumerable<string> productCategories =products.Select(p => p.Category).Distinct();  
AsEnumerable
  1. Table<Customer> custTable = GetCustomersTable();  
  2. var query = custTable.AsEnumerable().Where(c => IsGoodCustomer(c));  
ToArray
  1. string[] customerCountries =customers.Select(c => c.Country).Distinct().ToArray();  
ToList
  1. List<Customer> customersWithOrdersIn2005 =customers.  
  2. Where(c => c.Orders.Any(o => o.OrderDate.Year == 2005)).  
  3. ToList();  
ToDictionary
  1. Dictionary<int,Order> orders =customers.  
  2. SelectMany(c => c.Orders).  
  3. Where(o => o.OrderDate.Year == 2005).  
  4. ToDictionary(o => o.OrderID);  
  5. Dictionary<string,decimal> categoryMaxPrice =products.  
  6. GroupBy(p => p.Category).  
  7. ToDictionary(g => g.Key, g => g.Group.Max(p => p.UnitPrice));  
ToLookup
  1. Lookup<string,Product> productsByCategory =products.ToLookup(p => p.Category);  
  2. IEnumerable<Product> beverages = productsByCategory["Beverage"];  
OfType
  1. List<Person> persons = GetListOfPersons();  
  2. IEnumerable<Employee> employees = persons.OfType<Employee>();  
Cast
  1. ArrayList objects = GetOrders();  
  2. IEnumerable<Order> ordersIn2005 =  
  3. objects.  
  4. Cast<Order>().  
  5. Where(o => o.OrderDate.Year == 2005);  
  6. ArrayList objects = GetOrders();  
  7. IEnumerable<Order> ordersIn2005 =  
  8. from Order o in objects  
  9. where o.OrderDate.Year == 2005  
  10. select o;  
First
  1. string phone = "206-555-1212";  
  2. Customer c = customers.First(c => c.Phone == phone);  
Single
  1. int id=12345;  
  2. Customer c = customers.Single(c => c.CustomerID == id);  
ElementAt
  1. Product thirdMostExpensive = products.OrderByDescending(p => p.UnitPrice).ElementAt(2);  
Range
  1. int[] squares = Enumerable.Range(0, 100).Select(x => x * x).ToArray();  

 

Repeat

  1. long[] x = Enumerable.Repeat(-1L, 256).ToArray();  
Empty
  1. IEnumerable<Customer> noCustomers = Enumerable.Empty<Customer>();  
Any
  1. bool b = products.Any(p => p.UnitPrice >= 100 && p.UnitsInStock == 0);  
All
  1. IEnumerable<string> fullyStockedCategories =products.  
  2. GroupBy(p => p.Category).  
  3. Where(g => g.Group.All(p => p.UnitsInStock > 0)).  
  4. Select(g => g.Key);  
Count
  1. int count = customers.Count(c => c.City == "London");  
Sum
  1. int year = 2005;  
  2. var namesAndTotals = customers.  
  3. Select(c => new {  
  4.     c.Name,  
  5.         TotalOrders = c.Orders.  
  6.     Where(o => o.OrderDate.Year == year).  
  7.     Sum(o => o.Total)  
  8. });  
Min
  1. var minPriceByCategory = products.  
  2. GroupBy(p => p.Category).  
  3. Select(g => new {  
  4.     Category = g.Key,  
  5.         MinPrice = g.Group.Min(p => p.UnitPrice)  
  6. });  
Max
  1. decimal largestOrder = customers.  
  2. SelectMany(c => c.Orders).  
  3. Where(o => o.OrderDate.Year == 2005).  
  4. Max(o => o.Total);  
Average
  1. var averageOrderTotals = customers.  
  2. Select(c => new {  
  3.     c.Name,  
  4.         AverageOrderTotal = c.Orders.Average(o => o.Total)  
  5. });  
Aggregate
  1. var longestNamesByCategory = products.  
  2. GroupBy(p => p.Category).  
  3. Select(g => new {  
  4.     Category = g.Key,  
  5.         LongestName = g.Group.  
  6.     Select(p => p.Name).  
  7.     Aggregate((s, t) => t.Length > s.Length ? t : s)  
  8. });