Lambda expressions and anonymous methods on Metadata service in CRM 4.0


In C# 3.0 Microsoft has added lambda expression. This is not a new feature in computer languages originally designed on a conceptualized level way back in time by an American called Alonzo Church.


Lamda expressions provide shorthand syntax for algorithms.


I have played around with this and below is a simple example where I retrieve all entities from the CRM metadata service. I call my filter method and provide my delegate with the filter expression. I have also an example on using anonym’s method, in previous versions before 2.0 you had to write a named method and pass that name where the delegate was required. The syntax for C# operator is => and lambda expression. Example is simple and I’m only using one param1 (filter) and checks if entity is customizable.


        static void Main(string[] args)


        {


            //Login and retrive all entities from metadataservice (change name to your org)


            RetrieveAllEntitiesResponse allEntitiesResponse = Metadata.RetriveAll(“mydemo”);


 


            //Lambda expression


            EntityMetadata[] filterEntities = Common.FilterMetadata(allEntitiesResponse,


                filter => (filter.IsCustomizable.Value == true)


                );


 


            /*


            //Anonymous method


            EntityMetadata[] filterEntities = Common.FilterMetadata(allEntitiesResponse,


                delegate(EntityMetadata filter)


                {


                    return (filter.IsCustomizable.Value == false);


                });


            */


 


            //Write result to console


            int total = 0;


            foreach (EntityMetadata item in filterEntities)


            {


                Console.WriteLine(item.SchemaName);


                total++;


            }


            Console.WriteLine(“Return of record(s) {0}”, total);


            Console.ReadKey();


 


        }


 


If your filter is complex you might consider to create a named method. I have attached Visual Studio 2008 project for you to play around with.



 


Lambda on MSDN


 


This posting is provided “AS IS” with no warranties, and confers no rights.


 

LambdaExample.zip

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