How to wait for async method to finish when calling a external service in .net core?

Question

I have seen some of the existing questions regarding async waiting for completion , However for me none of the solution work.

I am using a C# wrapper for connecting to sales force https://github.com/developerforce/Force.com-Toolkit-for-NET/

In the below method i want to wait for the method UsernamePasswordAsync to complete execution so that i can get the values from the auth object.

public async Task<Token> GetTokenForSalesForce()
{
    Token token = null;
    try
    {
        var auth = new AuthenticationClient();
         await auth.UsernamePasswordAsync(configuration.Value.ClientId, configuration.Value.ClientSecert,
                                         configuration.Value.SFUsername, configuration.Value.SFPassword,
                                         configuration.Value.SFBaseUrl);
        if (!string.IsNullOrEmpty(auth.AccessToken) && !string.IsNullOrEmpty(auth.InstanceUrl))
        {
            token = new Token
            {
                BearerToken = auth.AccessToken,
                InstanceURL = auth.InstanceUrl,
                ApiVersion = auth.ApiVersion
            };
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
    return token;
}

public async Task<List<SFDashboardResponse>> GetOrderCountFromSalesForce(Token token)
{
    List<SFDashboardResponse> sFDashboardResponses = new List<SFDashboardResponse>();
    try
    {
        var client = new ForceClient(token.InstanceURL, token.BearerToken, token.ApiVersion);
        var response = await client.QueryAsync<SFDashboardResponse>("SELECT something ");
        var records = response.Records;
    }
    catch(Exception e)
    {

    }
    return sFDashboardResponses;
}

The signature in the library is

public async Task WebServerAsync(string clientId, string clientSecret, string redirectUri, string code, string tokenRequestEndpointUrl)
{
}

The problem is while the method wait for await to be first execute another thread executes the other part of the orignal caller.

I call it from here

public IActionResult post()
{
    var authtoken = _salesForceService.GetTokenForSalesForce();
    var response = _salesForceService.GetOrderCountFromSalesForce(authtoken.Result);
    DashboardModel dashboardModel = null;
    if (authtoken.Status == TaskStatus.RanToCompletion)
    {
       fill the object
    }

     return Ok(dashboardModel);
 }

I appreciate people who down vote a question , it would be nice if you put a reason with it — ankur
– ankur, Commented Aug 28, 2018 at 15:11
Never do throw ex; where ex is a caught exception. You'll lose your stack trace. Just do throw; which will preserve the stack trace. And don't catch an exception if the only thing you're going to do is re-throw it. And don't have an empty catch block in your code. At the very minimum, log the exception. — mason
– mason, Commented Aug 28, 2018 at 15:19
@mason you are correct. Logger is being implemented by another person. Once it is done it will be used in the catch block. — ankur
– ankur, Commented Aug 28, 2018 at 15:21
You're not awaiting the asynchronous tasks, so of course the code moves on. That's sort of the whole point. — Chris Pratt
– Chris Pratt, Commented Aug 28, 2018 at 15:30

Rey · Accepted Answer · 2018-08-28 15:26:49Z

You can wrap the IActionResult with a Task and await on the tasks below.

public async Task<IActionResult> post()
{
    var authtoken = await _salesForceService.GetTokenForSalesForce();
    var response = await _salesForceService.GetOrderCountFromSalesForce(authtoken);

    DashboardModel dashboardModel = //fill the object

    return Ok(dashboardModel);
}

At least this is what you are asking for as far as I understand, if its another problem let me know.

EDIT 1:

This is just my suggestion/opinion.

Personally I dont really like having the code wrapped in try-catch everywhere, this way the code can be hard to read and maintain. You really should consider centralizing exception handling in one place, you could have a base controller or just a middleware like this one:

public class ErrorHandlingMiddleware
{
    private readonly RequestDelegate _next;

    public ErrorHandlingMiddleware(RequestDelegate next)
    {
        this._next = next;
    }

    public async Task Invoke(HttpContext context, ILogger logger)
    {
        try
        {
            await _next(context);
        }
        catch (Exception ex)
        { 
            await HandleExceptionAsync(context, ex, logger);
        }
    }

    private static Task HandleExceptionAsync(HttpContext context, Exception exception, ILogger logger) 
    {
        logger.Log(exception);
        //do something
        return context.Response.WriteAsync(... something ...); //Maybe some JSON message or something
    }
}

The you just register it as a middleware in the Configure method like below:

app.UseMiddleware<ErrorHandlingMiddleware>();

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