WebAPIService class library (C#)

Artikkeli
01/06/2023

WebAPIService is a sample .NET 6.0 class library project that demonstrates several important capabilities that you should include when you use the Dataverse Web API.

This library demonstrates:

Managing Dataverse service protection limits with the .NET resilience and transient fault handling library Polly.
Managing an HttpClient in .NET using IHttpClientFactory.
Using configuration data to manage the behavior of the client.
Managing errors returned by Dataverse Web API.
A pattern of code reuse by:
- Creating classes that inherit from HttpRequestMessage and HttpResponseMessage.
- Methods that use those classes.
- A modular pattern for adding new capabilities as needed.

Note

This sample library is a helper that is used by all the Dataverse C# Web API samples, but it is not an SDK. It is tested only to confirm that the samples that use it run successfully. This sample code is provided 'as-is' with no warranty for reuse.

This library doesn't:

Manage authentication. It depends on a function passed from an application that provides the access token to use. All Web API samples depend on a shared App class that manages authentication using the Microsoft Authentication Library (MSAL). MSAL supports several different types of authentication flows. These samples use the Username/password (ROPC) flow for simplicity but this flow isn't recommended. For your apps, you should use one of the other flows. More information: Authentication flow support in the Microsoft Authentication Library.
Provide for any code generation capabilities. All classes used in the samples are written by hand. All business entity data uses the well-known Json.NET JObject Class rather than a class representing the entity type.
Provide an object model for composing OData queries. All queries show the OData query syntax as query parameters.

Code

You can find the WebApiService class library source code and Visual Studio solution at PowerApps-Samples/dataverse/webapi/C#-NETx/WebAPIService

Class list

The following are classes included in the WebAPIService.

Service Class

The Service class provides methods to send requests to Dataverse through an HttpClient managed using IHttpClientFactory.

The Service is the core component for all samples and you can use it to complete any operations demonstrated with sample code. Everything else that is included in the WebAPIService or any of the samples using it provides for reuse of code and allows for the capabilities of the Dataverse Web API to be demonstrated at a higher level.

The Service constructor accepts a Config class instance, which contains two required properties: GetAccessToken and Url. All the other properties represent options that have defaults.

The constructor uses dependency injection to create an IHttpClientFactory that can return a named HttpClient with the properties specified in the ConfigureHttpClient function. Whether or not this client uses cookies is based on whether the Config.DisableCookies parameter is set. In the constructor the policy defined by the static GetRetryPolicy method that controls how transient errors and Dataverse service protection limits are managed.

Service Methods

The Service class has the following methods:

SendAsync Method

This method is ultimately responsible for all operations.

This method:

Has an HttpRequestMessage parameter.
Returns Task<HttpResponseMessage>
Exposes the same signature as the HttpClient.SendAsync(HttpRequestMessage) Method and can be used in the same way.
Calls the function set in the Config.GetAccessToken method to set the Authorization header value for the request.
Uses the IHttpClientFactory.CreateClient Method to get the named HttpClient to send the request.
Throws a ServiceException if the HttpResponseMessage.IsSuccessStatusCode Property is false, so you don't need to check the IsSuccessStatusCode when using this method.

SendAsync<T> Method

This method facilitates returning a class that includes properties found in the ComplexTypes returned by OData Actions and Functions in Dataverse Web API.

Has an HttpRequestMessage parameter. When using this method it's expected, but not required, that the request parameter is one of the *Response classes that derive from HttpResponseMessage.
Returns Task<T> where T is a class derived from HttpResponseMessage. See *Response classes for more information.
Calls the SendAsync Method.
Uses the HttpResponseMessage As<T> extension method to return the requested type.

The following example shows use with the WhoAmI function:

static async Task WhoAmI(Service service)
{
   var response = await service.SendAsync<WhoAmIResponse>(new WhoAmIRequest());

   Console.WriteLine($"Your user ID is {response.UserId}");
}

ParseError Method

This method parses the content of an HttpResponseMessage for an unsuccessful HttpRequestMessage to return an ServiceException. The SendAsync method uses this method when the HttpResponseMessage.IsSuccessStatusCode Property is false. You can also use it to extract error information from HttpResponseMessage instances returned by BatchResponse.HttpResponseMessages when the BatchRequest.ContinueOnError property is set to true. More information: Batch

Service Properties

Service has a single property: BaseAddress.

BaseAddress Property

This property returns the base URL set in the Config.Url. You need this URL when instantiating the BatchRequest class and to append to a relative URL anytime an absolute URL is required.

Config Class

The Config class contains properties that control the behavior of the application as shown in the following table:

Property	Type	Description
`GetAccessToken`	`Func<Task<string>>`	A function provided by the client application to return an access token.
`Url`	`string?`	The base Url of the environment. For example: `https://org.api.crm.dynamics.com`
`CallerObjectId`	`Guid`	The SystemUser.ActiveDirectoryGuid value to apply for impersonation. Default is Guid.Empty More information: Impersonate another user using the Web API
`TimeoutInSeconds`	`ushort`	How long to wait for a timeout. Default is 120 seconds.
`MaxRetries`	`byte`	Maximum number of times to retry when service protection limits occur. Default is 3.
`Version`	`string`	The version of the service to use. Default is `v9.2`
`DisableCookies`	`bool`	Whether to disable cookies to gain performance in bulk data load scenarios. More information: Server affinity

EntityReference Class

The EntityReference class represents a reference to a record in a Dataverse table. OData identifies resources with a URL. EntityReference provides methods to make it easier create and access properties of Urls.

EntityReference Constructors

Use the following constructors to instantiate an EntityReference.

EntityReference(string entitySetName, Guid? ID)

Creates an entity reference using the EntitySetName and a Guid.

EntityReference(string uri)

Parses an absolute or relative url to create an entity reference, including Urls that use alternate keys.

EntityReference(string setName, Dictionary<string, string>? keyAttributes)

Use this constructor to instantiate an entity reference using an alternate key.

Note

The key values must be string values. This does not convert other types to appropriate strings.

EntityReference Properties

EntityReference has the following public properties:

Property	Type	Description
`Id`	`Guid?`	The primary key value of the record when not using an alternate key.
`KeyAttributes`	`Dictionary<string, string>`	The string values that represent alternate key values used in a url.
`SetName`	`string`	The `EntitySetName` of the entity type.
`Path`	`string`	A relative url to the record.

EntityReference Methods

EntityReference has the following public methods. Neither of them require any parameters.

Method Name	Return Type	Description
`AsODataId`	`string`	Returns a string formatted for use as a parameter reference to a record in the URL for an OData Function.
`AsJObject`	`JObject`	Returns a `JObject` that can be used as a parameter reference to a record in an OData Action.

Error Classes

ODataError, Error, and ODataException are classes used to deserialize errors returned by the service. You don't need to work with them directly.

ServiceException

ServiceException is an Exception class that contains properties of the error returned by the service. Use the ParseError Method to get an instance of this exception.

Extensions

WebApiService has one extension method from a .NET type.

HttpResponseMessage As<T>

This extension instantiates an instance of T where T is derived from HttpResponseMessage and copies the properties of the HttpResponseMessage to the derived class. The Service SendAsync<T> Method uses this method, but can also be used separately. For example, when using the BatchRequest class, the items in the BatchResponse.HttpResponseMessages are HttpResponseMessage types. You can use this extension to convert them to the appropriate derived class to facilitate accessing any properties.

Messages

The Messages folder includes classes that inherit from HttpRequestMessage or HttpResponseMessage.

These classes provide reusable definitions of requests and responses that correspond to OData operations you can use in any Dataverse environment.

These classes also provide examples of specific operations that can be applied using HttpRequestMessage and HttpResponseMessage without deriving from those types.

Within an application, you might also create custom messages, for example representing a custom API in your environment, using the same pattern. These are modular classes and aren't required to be included in the WebAPIService.Messages folder.

For example, the Web API Functions and Actions Sample (C#) uses a custom API that isn't included in Dataverse until a solution containing the custom API is installed. The definition for the corresponding classes to use this message are located in the sample application that uses it:

*Request classes

These classes generally have a constructor with parameters that instantiates a HttpRequestMessage with the data needed to perform the operation. They can have separate properties as appropriate.

The most simple example of this pattern is the WhoAmIRequest class.

namespace PowerApps.Samples.Messages
{
    /// <summary>
    /// Contains the data to perform the WhoAmI function
    /// </summary>
    public sealed class WhoAmIRequest : HttpRequestMessage
    {
        /// <summary>
        /// Initializes the WhoAmIRequest
        /// </summary>
        public WhoAmIRequest()
        {
            Method = HttpMethod.Get;
            RequestUri = new Uri(
                uriString: "WhoAmI", 
                uriKind: UriKind.Relative);
        }
    }
}

The names of these classes generally align with the classes in the Dataverse SDK Microsoft.Xrm.Sdk.Messages Namespace but aren't limited to those operations. Web API provides for performing some operations that can't be done with the SDK, for example CreateRetrieveRequest is message that creates a record and retrieves it. The Dataverse SDK doesn't provide this capability in a single request.

*Response classes

When *Request classes return a value, there's a corresponding *Response class to access the returned properties. If the *Request returns 204 No Content, the operation returns an HttpResponseMessage but there's no derived class. Use the SendAsync method to send these requests.

*Response classes provide typed properties that access the HttpResponseMessage Headers or Content properties and parse them to provide access to the Complex Type returned by the operation.

The WhoAmIResponse class is an example. Within this class you can find all the code needed to extract the properties of the WhoAmIResponse ComplexType.

using Newtonsoft.Json.Linq;

namespace PowerApps.Samples.Messages
{
    // This class must be instantiated by either:
    // - The Service.SendAsync<T> method
    // - The HttpResponseMessage.As<T> extension in Extensions.cs

    /// <summary>
    /// Contains the response from the WhoAmIRequest
    /// </summary>
    public sealed class WhoAmIResponse : HttpResponseMessage
    {

        // Cache the async content
        private string? _content;

        //Provides JObject for property getters
        private JObject _jObject
        {
            get
            {
                _content ??= Content.ReadAsStringAsync().GetAwaiter().GetResult();

                return JObject.Parse(_content);
            }
        }

        /// <summary>
        /// Gets the ID of the business to which the logged on user belongs.
        /// </summary>
        public Guid BusinessUnitId => (Guid)_jObject.GetValue(nameof(BusinessUnitId));

        /// <summary>
        /// Gets ID of the user who is logged on.
        /// </summary>
        public Guid UserId => (Guid)_jObject.GetValue(nameof(UserId));

        /// <summary>
        /// Gets ID of the organization that the user belongs to.
        /// </summary>
        public Guid OrganizationId => (Guid)_jObject.GetValue(nameof(OrganizationId));
    }
}

These classes can only be properly instantiated when returned by the SendAsync<T> Method or by using the HttpResponseMessage As<T> extension on an HttpResponseMessage in the BatchResponse.HttpResponseMessages property.

Batch

The Batch folder contains three classes to manage sending OData $batch requests. More information: Execute batch operations using the Web API.

BatchRequest

The BatchRequest constructor initializes an HttpRequestMessage that can be used with SendAsync<T> Method to send requests in batches. The constructor requires the Service.BaseAddress value to be passed as a parameter.

BatchRequest has the following properties.

Property	Type	Description
`ContinueOnError`	`Bool`	Controls whether the batch operation should continue when an error occurs.
`ChangeSets`	`List<ChangeSet>`	One or more change sets to be included in the batch.
`Requests`	`List<HttpRequestMessage>`	One or more `HttpMessageRequest` to be sent outside of any `ChangeSet`.

When ChangeSets or Requests are set, they're encapsulated into HttpMessageContent and added to the Content of the request. The private ToMessageContent method applies the required changes to headers and returns the HttpMessageContent for both ChangeSets and Requests properties.

ChangeSet

A change set represents a group of requests that must complete within a transaction.

It contains a single property:

Property	Type	Description
`Requests`	`List<HttpRequestMessage>`	One or more `HttpMessageRequest` to be performed within the transaction.

BatchResponse

BatchResponse has a single property:

Property	Type	Description
`HttpResponseMessages`	`List<HttpResponseMessage>`	The responses from the `$batch` operation.

BatchResponse has a private ParseMultipartContent method used by the HttpResponseMessages property getter to parse the MultipartContent returned into individual HttpResponseMessage.

To access type properties of the HttpResponseMessage instances returned, you can use the HttpResponseMessage As<T> extension method.

Methods

For operations that are frequently performed, the Methods folder contains extensions of the Service class. These methods allow for using the corresponding *Request classes in a single line.

The following methods are included:

Method	Return Type	Description
`Create`	`Task<EntityReference>`	Creates a new record.
`CreateRetrieve`	`Task<JObject>`	Creates a new record and retrieves it.
`Delete`	`Task`	Deletes a record.
`FetchXml`	`Task<FetchXmlResponse>`	Retrieves the results of a FetchXml query. Request is sent with `POST` using `$batch` to mitigate issues where long URLs sent with `GET` can exceed limits.
`GetColumnValue<T>`	`Task<T>`	Retrieves a single column value from a table row.
`Retrieve`	`Task<JObject>`	Retrieves a record.
`RetrieveMultiple`	`Task<RetrieveMultipleResponse>`	Retrieves multiple records.
`SetColumnValue<T>`	`Task`	Sets the value of a column for a table row.
`Update`	`Task`	Updates a record.
`Upsert`	`Task<UpsertResponse>`	Performs an Upsert on a record.

Within a sample application using WebAPIService, when the operation doesn't represent an API found in Dataverse by default, the method is defined in the application rather than in the WebAPIService.

For example, the Web API Functions and Actions Sample (C#) uses a custom API that isn't included in Dataverse until a solution containing the custom API is installed. The definition for this method is located in the sample application that uses it: FunctionsAndActions/Methods/IsSystemAdmin.cs

Types

The Types folder contains any classes or enums that correspond to ComplexTypes or EnumTypes needed as parameters or response properties for messages.

Metadata

The Metadata folder contains Messages and Types specific to operations that work with Dataverse Schema definitions. These classes frequently have many properties that return complex types. These types are used in the Web API table schema operations sample (C#).

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