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
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