The programming models for Microsoft Dynamics 365


Applies To: Dynamics 365 (online), Dynamics 365 (on-premises), Dynamics CRM 2016, Dynamics CRM Online

Microsoft Dynamics 365 offers several programming models designed to give you the flexibility to decide what works best for your needs.

The following diagram illustrates the key programmability scenarios for Microsoft Dynamics 365 (online & on-premises). Use the appropriate Microsoft Dynamics 365 programming models for the type of solutions you create.

Programmability Scenarios for CRM 2016

In this topic

Connecting to Microsoft Dynamics 365

Extending on the server

Extending in the application

Connecting to Microsoft Dynamics 365

When you write clients to access data in Microsoft Dynamics 365 you have two options: you can use the Web API or the organization service.


The Web API was introduced with Microsoft Dynamics 365 and it provides a development experience that can be used across a wide variety of programming languages, platforms, and devices. The Web API implements the OData (Open Data Protocol) v4. OData is an OASIS standard for building and consuming RESTfulAPIs over rich data sources.

When you use the Web API, you can choose from a list of community-supported libraries that support the OData v4 standard. You can also choose to write code using HTTP directly. More information: Use the Microsoft Dynamics 365 Web API

When you connect to Microsoft Dynamics 365 (online) or on-premises environments with Internet-facing deployment (IFD), you can use Azure AD Authentication Libraries (ADAL) to enable authentication from a wide variety of programming languages and platforms. More information: Authenticate to Microsoft Dynamics 365 with the Web API


The organization data service (or OData endpoint) is an OData v2 service that was deprecated in Microsoft Dynamics 365 in favor of the Web API. The organization data service isn’t included in the preceding diagram. The organization service is still available to support code that used it. However, for any new development for Microsoft Dynamics 365 we recommend using the Web API. More information: Use the OData endpoint with web resources

Organization service

If you are a .NET developer you can use either the Web API or the organization service. With the organization service you can use a set of assemblies and tools to generate strongly typed classes that include custom entities and attributes that have been added to an instance of Microsoft Dynamics 365.

With SDK assemblies and tools for code generation you can also include an OrganizationServiceContext, which is based on the same concept as the DataServiceContext in Windows Communication Foundation (WCF) Data Services. This class lets you track changes, manage identities and relationships, and gives you access to the Microsoft Dynamics 365.NET Language-Integrated Query (LINQ) provider so you can build queries using LINQ. When you use the tools for code generation, you get strongly typed classes for entities and attributes that are defined when the code generation tool is run. These are called early-bound classes. More information: Use the early bound entity classes in code

When your code needs to work with entities and attributes that weren’t known at the time that the code generation tools were run, you can use an Entity class that allows for specifying entities and entity attribute in your code. This late-bound style of writing code provides greater flexibility but doesn’t allow for compile-time checking of all types so that no implicit casts occur. Late binding checks types only when the object is created or an action is performed on the type. The Entity class requires types to be explicitly specified to prevent implicit casts. More information: Use the late bound entity class in code

If you create a Windows client or are using Windows PowerShell, Xrm.Tooling provides a set of APIs that use the SDK assemblies to provide additional capabilities and resources specifically for Windows client development. More information: Build Windows client applications using the XRM tools

Extending on the server

You can write code that listens for events and applies custom business logic to modify or augment the standard behavior of the platform. This code is only available to be written using .NET managed code and the developer experience is based on the same objects defined in the SDK assemblies. You can work with the organization service to perform operations with Microsoft Dynamics 365 data. More information: Write plug-ins to extend business processes.

You can also create custom processes based on the Windows Workflow Foundation programming model. You can create several different types of processes. Most of the time you’ll use the workflow designer. But when there is some capability you can’t achieve in the designer, you can define processes using code. More information: Automate business processes using Dynamics 365 process

Extending in the application

Each of the client applications provided by Microsoft Dynamics 365 includes the ability to define customizations and deploy to multiple types of clients. The web application, Microsoft Dynamics 365 for Outlook, Dynamics 365 for tablets, and Dynamics 365 for phones each provide capabilities to include custom navigation and command options as well as the Xrm.Page object model and Xrm.Utility functions you can use with JavaScript to provide responsive experiences in the client. JavaScript libraries, HTML pages, images, and other types of files that can be used or displayed in the client are available as URL addressable web resources. More information: Use JavaScript with Microsoft Dynamics 365 and Web resources for Microsoft Dynamics 365.

When you need to access Microsoft Dynamics 365 data that isn’t available in the context where your JavaScript code is running, you can make calls to the server to get the data you need. The organization service can be used, but it is much easier to use the Web API with JSON rather than the XML required by the organization service. Because your script runs in the context of the application, you are automatically authenticated. More information: Get started with the Microsoft Dynamics 365 Web API (client-side JavaScript)

See Also

How do I?
Tutorials and resources for learning about development for Microsoft Dynamics 365
Best practices for developing with Microsoft Dynamics 365
Developer tools

Microsoft Dynamics 365

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