Using LINQ query expressions to create an IN-Memory collection or "Table" .

In this article I will give you a simple ways to query an in-memory collection or "table" using LINQ query expressions. The focus will be on a particular part of a query expression called a query operator. Query operators such as select, where, join and groupby are the primary engine driving LINQ queries.Rather than directly access a database server, I will show how to use a new feature called collection initializers to quickly create an in-memory collection that will act just like a database table. By working with an in-memory "table" you can see how the syntax for querying a database works without having to connect directly to a database server.

The query operators are declared in a static class called System.Query.Sequence. They are stored in an assembly called System.Query.dll.

Collection Initializers

class Operator
     {
         public int OperatorID;
         public string OperatorName;
         public string OperatorType;
      }
 private List<Operator> OperatorList;
 private void CreateLists()
     {
         // Collection initializer
         OperatorList =
            new List<Operator>
             {
                { OperatorID = 1, OperatorName = "Where",
                  OperatorType = "Restriction" },
                { OperatorID = 2, OperatorName = "Select",
                   OperatorType = "Projection" },
                { OperatorID = 3, OperatorName = "SelectMany",
                   OperatorType = "Projection" }
             }
    } 

CONCLUSION

You can see that Operator has three fields called OperatorId, OperatorName, and OperatorType. All three fields are initialized in this example. The end result is a list containing three instances of the Operator class.