Where do you put your “secret sauce”, your business logic in SharePoint add-ins that are done entirely with JavaScript? How do you send emails? Do you copy the same code, the same business logic over and over again to each add-in?

The answer is: No, I use code behind, C#. I use Web API.

Add-ins example with C#

Web API allows us to build a RESTful web service that can be accessed and consumed from JavaScript. It allows us to keep light-weight JavaScript based web parts and add-ins on SharePoint pages. A SharePoint add-in that consumes a Web API just might be called a hybrid SharePoint add-in with JavaScript “on-premise” in SharePoint and C# in the cloud as active part of the solution.

In addition, Web API is not restricted to an add-in. We can access the same service from different add-ins. The Web API is consumed by a logic layer in each add-in. It solves the exact same task in each add-in. The Web API is a horizontal layer with business logic in our solution.

Why don’t you just build SharePoint provider add-ins?

1. Business logic such as sending an email could be built as a Web API even for SharePoint provider add-ins built with C#
2. SharePoint provider add-ins require additional infrastructure and hosting. Relatively small and occasional tasks such as sending an email do not justify the additional infrastructure
3. The cost of the additional infrastructure does not fit into the free/low cost model many SharePoint add-ins are sold for. SharePoint add-ins are in many cases downloaded to hundreds or thousands of clients. The cost of hosting a free SharePoint add-in should by all means be rather inexpensive.

What do we need to consume the Web API in JavaScript?

1. We need a few lines of code to make a request

var url = “http://secretsauce.azurewebsites.net/api/validation/Validate/” + appname;

var request = new SP.WebRequestInfo();

request.set_url(url);

request.set_method(“GET”);

response = SP.WebProxy.invoke(context, request);

context.executeQueryAsync(function onWent(sender, args) {

var responseBody = JSON.parse(response.get_body());

var validation = responseBody.AppValid;

if (validation) {}

2. We have to add the Web API URL as remote endpoint

How to build a Web API?

Despite ASP.Net Core 1.0 (formerly ASP.NET 5) is yet to be released, there are many fine tutorials about how to build a Web API. Here is a walkthrough of what I did to make it work.

1. In Visual Studio 2015, select “Cloud” and “ASP.NET Web Application”

Visual Studio 2015 –> Cloud –> ASP.NET Web Application

2. Then select “Web API”, ASP.NET Core 1.0 (Formerly ASP.NET 5) Template

Select Web API

3. I’ve built a very simple logic. I’ve built app business logic (AppBL) model:

public class AppBL

{

public string AppName { get; set; }

public bool AppValid { get; set; }

}

4. And I’ve built interface repository and repository and “validate” function:

public AppBL Validate(string appName)

{

AppBL item = new AppBL();

item.AppName = appName;

{

case “Carousel”:

item.AppValid = true;

break;

case “SimpleNewsLite”:

item.AppValid = true;

break;

}

return item;

}

5. I also added a controller and defined a HttpGET function:

[HttpGet(“validate/{appName}”)]

public IActionResult validate(string appName)

{

var item = Apps.Validate(appName);

return new ObjectResult(item);

}

[FromServices]

public IBLRepository Apps { get; set; }

6. In the startup.cs, I enabled cross-domain:

services.AddCors(options =>

options.AddPolicy(“AllowAll”, p => p.AllowAnyOrigin()

.AllowAnyMethod()

.AllowAnyHeader()));

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