How to call a WebAPI from Windows Service

Question

I have an application written in Windows Service and this app need to make a call to a WebAPI written in Asp.Net MVC 4 WebAPi. this method in WebAPI return a DTO with primitive type, something like:

class ImportResultDTO {
   public bool Success { get; set; }
   public string[] Messages { get; set; }
}

and in my webapi

public ImportResultDTO Get(int clientId) {
   // process.. and create the dto result.
   return dto;
}

My question is, how can I call the webApi from the Windows Service? I have my URL and value of parameter, but I don't know how to call and how to deserialize the xml result to the DTO.

Thank you

Solution 1

You could use System.Net.Http.HttpClient. You will obviously need to edit the fake base address and request URI in the example below but this also shows a basic way to check the response status as well.

// Create an HttpClient instance
HttpClient client = new HttpClient();
client.BaseAddress = new Uri("http://localhost:8888/");

// Usage
HttpResponseMessage response = client.GetAsync("api/importresults/1").Result;
if (response.IsSuccessStatusCode)
{
    var dto = response.Content.ReadAsAsync<ImportResultDTO>().Result;
}
else
{
    Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
}

Solution 2

You can install this NuGet package Microsoft ASP.NET Web API Client Libraries to your Windows Service project.

Here is a simple code snippet demonstrating how to use HttpClient:

        var client = new HttpClient();
        var response = client.GetAsync(uriOfYourService).Result;
        var content = response.Content.ReadAsAsync<ImportResultDTO>().Result;

(I'm calling .Result() here for the sake of simplicity...)

For more sample of HttpClient, please check this out: List of ASP.NET Web API and HttpClient Samples.

Comments

[Felipe Oriani]

Thank you blins, is there any way to check if the URL of my WebAPI is availible before I call client.GetAsync(...).Result ? I mean it because the internet connection or my webapi could be unstable and I need to check it before to do a correct eventLog for it. Thank you.

[Felipe Oriani]

Thank you Maggie. I vote up your awser. Is there any way to check if the URL of my WebAPI is availible before I call client.GetAsync(...).Result ? I mean it because the internet connection or my webapi could be unstable and I need to check it before to do a correct eventLog for it. Thank you.

[blins]

Could you not just wrap the call to GetAysnc in a try/catch block and handle the possible Exception? Try it and follow the stack trace, the inner exceptions look like what you are after (e.g. "No connection could be made because...")