How should I implement ExecuteAsync with RestSharp

问题:

I'm attempting to use the documentation on the RestSharp GitHub wiki to implement calls to my REST API service but I'm having an issue with the ExecuteAsync method in particular.

Currently my code looks like this for the API class:

public class HarooApi
{
    const string BaseUrl = "https://domain.here";

    readonly string _accountSid;
    readonly string _secretKey;

    public HarooApi(string accountSid, string secretKey)
    {
        _accountSid = accountSid;
        _secretKey = secretKey;
    }

    public T Execute<T>(RestRequest request) where T : new()
    {
        var client = new RestClient();
        client.BaseUrl = BaseUrl;
        client.Authenticator = new HttpBasicAuthenticator(_accountSid, _secretKey);
        request.AddParameter("AccountSid", _accountSid, ParameterType.UrlSegment);
        client.ExecuteAsync<T>(request, (response) =>
        {
            return response.Data;
        });
    }
}

I'm aware this slightly deviates from what is on the GitHub page but I'm using this with WP7 and believe the example is for C# hence the usage of the ExecuteAsync method.

My problem is with what the ExecuteAsync command should contain. I can't use return response.Data because I'm warned:

'System.Action<RestSharp.RestResponse<T>,RestSharp.RestRequestAsyncHandle>' returns void, a return keyword must not be followed by an object expression

Does anyone have any insight on how to fix this or a tutorial that may assist?

回答1:

Your code should look something like this:

public class HarooApi
{
    const string BaseUrl = "https://domain.here";

    readonly string _accountSid;
    readonly string _secretKey;

    public HarooApi(string accountSid, string secretKey)
    {
        _accountSid = accountSid;
        _secretKey = secretKey;
    }

    public void ExecuteAndGetContent(RestRequest request, Action<string> callback)
    {
        var client = new RestClient();
        client.BaseUrl = BaseUrl;
        client.Authenticator = new HttpBasicAuthenticator(_accountSid, _secretKey);
        request.AddParameter("AccountSid", _accountSid, ParameterType.UrlSegment);
        client.ExecuteAsync(request, response =>
        {
            callback(response.Content);
        });
    }

    public void ExecuteAndGetMyClass(RestRequest request, Action<MyClass> callback)
    {
        var client = new RestClient();
        client.BaseUrl = BaseUrl;
        client.Authenticator = new HttpBasicAuthenticator(_accountSid, _secretKey);
        request.AddParameter("AccountSid", _accountSid, ParameterType.UrlSegment);
        client.ExecuteAsync<MyClass>(request, (response) =>
        {
            callback(response.Data);
        });
    }
}

I added two methods, so you can check what you want (string content from the response body, or a deserialized class represented here by MyClass)

回答2:

Old question but if you are using C# 5 you can have a generic execute class by creating a TaskCompleteSource that resturns a Task of T. Your code could look like this:

public Task<T> ExecuteAsync<T>(RestRequest request) where T : new()
    {
        var client = new RestClient();
        var taskCompletionSource = new TaskCompletionSource<T>();
        client.BaseUrl = BaseUrl;
        client.Authenticator = new HttpBasicAuthenticator(_accountSid, _secretKey);
        request.AddParameter("AccountSid", _accountSid, ParameterType.UrlSegment);
        client.ExecuteAsync<T>(request, (response) => taskCompletionSource.SetResult(response.Data));
        return taskCompletionSource.Task;
    }

And use it like this:

private async Task DoWork()
    {
        var api = new HarooApi("MyAcoountId", "MySecret");
        var request = new RestRequest();
        var myClass = await api.ExecuteAsync<MyClass>(request);

        // Do something with myClass
    }

回答3:

As an alternative (or complement) to the fine answer by Gusten. You can use ExecuteTaskAsync. This way you do not manually have to handle TaskCompletionSource. Note the async keyword in the signature.

public async Task<T> ExecuteAsync<T>(RestRequest request) where T : new()
{
    var client = new RestClient();
    client.BaseUrl = BaseUrl;
    client.Authenticator = new HttpBasicAuthenticator(_accountSid, _secretKey);
    request.AddParameter("AccountSid", _accountSid, ParameterType.UrlSegment);
    IRestResponse<T> response = await client.ExecuteTaskAsync<T>(request);
    return response.Data;
}

回答4:

Or more precisely like this:

    public async Task<IRestResponse<T>> ExecuteAsync<T>(IRestRequest request) where T : class, new()
    {
        var client = new RestClient(_settingsViewModel.BaseUrl);

        var taskCompletionSource = new TaskCompletionSource<IRestResponse<T>>();
        client.ExecuteAsync<T>(request, restResponse =>
        {
            if (restResponse.ErrorException != null)
            {
                const string message = "Error retrieving response.";
                throw new ApplicationException(message, restResponse.ErrorException);
            }
            taskCompletionSource.SetResult(restResponse);
        });

        return await taskCompletionSource.Task;
    }

回答5:

The following did the job

public async Task<IRestResponse<T>> ExecuteAsync<T>(IRestRequest request) where T : class, new()
{
    var client = new RestClient
    {
        BaseUrl = _baseUrl,
        Authenticator = new HttpBasicAuthenticator(_useraname, _password),
        Timeout = 3000,
    };

    var tcs = new TaskCompletionSource<T>();
    client.ExecuteAsync<T>(request, restResponse =>
    {
        if (restResponse.ErrorException != null)
        {
            const string message = "Error retrieving response.";
            throw new ApplicationException(message, restResponse.ErrorException);
        }
        tcs.SetResult(restResponse.Data);
    });

    return await tcs.Task as IRestResponse<T>;

}