Getting an early-bound relationship

Question

When I am linking annotations to a specific entity, rather than creating a relationship like so:

var associateRequest = new AssociateRequest
{
    Target = new EntityReference(SalesOrder.EntityLogicalName, salesOrderGuid),
    RelatedEntities = new EntityReferenceCollection
    {
        new EntityReference(Annotation.EntityLogicalName, noteGuid),
    },
    Relationship = new Relationship("SalesOrder_Annotation")
};

Is it possible to reference the relationship in a strongly typed way:

var associateRequest = new AssociateRequest
{
    Target = new EntityReference(SalesOrder.EntityLogicalName, salesOrderGuid),
    RelatedEntities = new EntityReferenceCollection
    {
        new EntityReference(Annotation.EntityLogicalName, noteGuid)
    },
    Relationship = SalesOrder.Relationships.SalesOrder_Annotation // <----- ???
};

This would be similar to being able to get the logicalname at develop time:

SalesOrder.EntityLogicalName

Can we reference the specific 1:N relationship the same way:

SalesOrder.Relationships.SalesOrder_Annotation

Answer 1

The value you are looking for is stored in a code attribute, RelationshipSchemaNameAttribute, if you generate your code using the standard CrmSvcUtil.exe application provided in the SDK (\SDK\Bin\CrmSvcUtil.exe). I've validated this code in a console application using the early bound entity class file provided in the SDK (\SDK\SampleCode\CS\HelperCode\MyOrganizationCrmSdkTypes.cs).

Call the method as follows (per your example):

var relationship = GetRelationship<SalesOrder>(nameof(SalesOrder.SalesOrder_Annotation))

Or if you want to return the actual string value:

var relationshipName = GetRelationshipSchemaName<SalesOrder>(nameof(SalesOrder.SalesOrder_Annotation))

Add this code to a helper class in your application:

public static string GetRelationshipSchemaName<T>(string relationshipPropertyName) where T:Entity
{
    return typeof (T).GetProperties()
        .FirstOrDefault(x => x.Name == relationshipPropertyName)
        .GetCustomAttributes()
        .OfType<RelationshipSchemaNameAttribute>()
        .FirstOrDefault()
        ?.SchemaName;            
}

public static Relationship GetRelationship<T>(string relationshipPropertyName) where T : Entity
{
    return new Relationship(typeof(T).GetProperties()
        .FirstOrDefault(x => x.Name == relationshipPropertyName)
        .GetCustomAttributes()
        .OfType<RelationshipSchemaNameAttribute>()
        .FirstOrDefault()
        ?.SchemaName);
}

This is what your updated code would look like:

var associateRequest = new AssociateRequest
                                   {
                                       Target =
                                           new EntityReference(
                                               SalesOrder.EntityLogicalName,
                                               salesOrderGuid),
                                       RelatedEntities =
                                           new EntityReferenceCollection
                                               {
                                                   new EntityReference(
                                                       Annotation
                                                           .EntityLogicalName,
                                                       noteGuid)
                                               },
                                       Relationship = GetRelationship<SalesOrder>(nameof(SalesOrder.SalesOrder_Annotation)) ///////////????
                                   };

Answer 2

On second thought ,my t4 template answer seems an overkill
You can use expression trees and an extension method to easily get what you need

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

namespace ConsoleApplication9
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            Relationship r = new Class1().GetRelationShip(s => s.RelationShipProperty);
            Console.WriteLine(r.Name);
            System.Console.ReadLine();
        }
    }

    public static class MyExtention
    {
        public static Relationship GetRelationShip<T, TProperty>(this T t, Expression<Func<T, TProperty>> expression)
        {
            return new Relationship(((expression.Body as MemberExpression).Member as PropertyInfo)
                    .GetCustomAttributes(typeof(RelationshipAttribute))
                    .Select(a=>(RelationshipAttribute)a)
                    .First().Name
                    );
        }
    }

    public class RelationshipAttribute : System.Attribute
    {
        public string Name { get; set; }

        public RelationshipAttribute(string name)
        {
            Name = name;
        }
    }

    public class Relationship
    {
        public string Name { get; set; }

        public Relationship(string name)
        {
            Name = name;
        }
    }

    public class Class1
    {
        [Relationship("RelationShipA")]
        public List<int> RelationShipProperty { get; set; }
    }
}