How to implement NOT IN clause in LINQ/LAMBDA Query expression?Explain with an example.

Answer:

This can be done by negating the "Contains" extension method . Example follows.

Suppose we have a person class as under

public class Person

{

	public string  PersonName { get; set; }

	public string JobTitle { get; set; }



	public override string ToString()

	{

		return "Person Name: " + PersonName + " JobTitle:" + JobTitle;

	}

}

Then populate the Person collection as under

private static List<Person> PreparePersonCollection()

{

	List<Person> lstPersonCollection = new List<Person>();

	lstPersonCollection.Add(new Person { PersonName = "Amitav Sen", JobTitle = "Design Engineer" });

	lstPersonCollection.Add(new Person { PersonName = "Bhavini Dey", JobTitle = "Software Engineer" });

	lstPersonCollection.Add(new Person { PersonName = "Debasis Basu", JobTitle = "Software Engineer" });

	lstPersonCollection.Add(new Person { PersonName = "Kartik Moin", JobTitle = "Lead Engineer" });

	lstPersonCollection.Add(new Person { PersonName = "Shahjahan Khan", JobTitle = "Technical Lead" });



	return lstPersonCollection;

}

Suppose we want to get the list of Person who does not has job Title as "Design Engineer", "Software Engineer".

The complete query will be as under

List<Person> source = PreparePersonCollection();



string[] strJobTitleToInclude = new string[] { "Design Engineer", "Software Engineer" };



//Linq Version



(from s in source

 where !strJobTitleToInclude.Contains(s.JobTitle)

  select s)

.ToList()

.ForEach(i => Console.WriteLine(i.ToString()));

           

//Lambda Version

source

	.Where(i => !strJobTitleToInclude.Contains(i.JobTitle))

	.ToList()

	.ForEach(i => Console.WriteLine(i.ToString()));

Output

Person Name: Kartik Moin JobTitle:Lead Engineer

Person Name: Shahjahan Khan JobTitle:Technical Lead