Question

这是我的HttpService类，它运行正常。但它看起来很奇怪，每个函数中的代码都大致相同。我应该在每个函数中编写try / catch，特别是TaskCanceledException，如果我没有在这里捕获它，我的应用程序将终止。有人可以给我一些关于如何优化代码的例子吗？

[Export(typeof(IDataSource))]
public class HttpService : IDataSource
{
    HttpClient client = new HttpClient();
    public HttpService()
    {
        client.BaseAddress = new Uri("https://localhost:3721");
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
    }

    public void Initialize(CurrentUser currentUser)
    {
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic",
            Convert.ToBase64String(Encoding.UTF8.GetBytes(currentUser.Name + ":" + currentUser.Password)));
    }

    public async Task<IEnumerable<User>> getUsers()
    {
        try
        {
            var response = await client.GetAsync("api/User");
            //response.EnsureSuccessStatusCode(); // Throw on error code.
            if (response.IsSuccessStatusCode)
            {
                var result = await response.Content.ReadAsAsync<IEnumerable<User>>();
                return result;
            }
            else
            {
                return null;
            }
        }
        catch (Newtonsoft.Json.JsonException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        catch (HttpRequestException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        catch (TaskCanceledException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        return null;
    }

    public async Task<IEnumerable<permission>> getPermission()
    {
        try
        {
            var response = await client.GetAsync("api/User");
            //response.EnsureSuccessStatusCode(); // Throw on error code.
            if (response.IsSuccessStatusCode)
            {
                var result = await response.Content.ReadAsAsync<IEnumerable<permission>>();
                return result;
            }
            else
            {
                return null;
            }
        }
        catch (Newtonsoft.Json.JsonException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        catch (HttpRequestException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        catch (TaskCanceledException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        return null;
    }

    public async Task<CurrentUser> getCurrentUserInfo(User user)
    {
        try
        {
            var response = await client.GetAsync("api/User?name=" + user.Name);
            if (response.IsSuccessStatusCode)
            {
                var result = await response.Content.ReadAsAsync<CurrentUser>();
                return result;
            }
            else
            {

                return null;
            }
        }
        catch (Newtonsoft.Json.JsonException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        catch (HttpRequestException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        catch (TaskCanceledException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        return null;
    }

}

Answer 1

如果我在这里没有抓到它，我的申请将会终止。

不，这根本不是真的;它是调用的代码它也有机会（实际上是责任）来处理错误。例如：

try {
    var permission = await getPermission();
    //...
} catch(Exception ex) {
    // log, whatever
}

将异常处理放在最合适的位置可以减少async方法中不必要的代码。您当前正在做的是让您的async方法假装没有发生任何不良事件 - 这不是最佳做法。

Answer 2

免责声明：我无法编译，因此您可能需要按摩它。

我看到你唯一能做的就是制作一个这样的方法：

public async Task<T> getAsync(string url)
{
    try
    {
        var response = await client.GetAsync(url);
        if (response.IsSuccessStatusCode)
        {
            var result = await response.Content.ReadAsAsync<T>();
            return (T)result;
        }
        else
        {
            return null;
        }
    }
    catch (Newtonsoft.Json.JsonException ex)
    {
        Console.WriteLine(ex.ToString());
    }
    catch (HttpRequestException ex)
    {
        Console.WriteLine(ex.ToString());
    }
    catch (TaskCanceledException ex)
    {
        Console.WriteLine(ex.ToString());
    }
    return null;
}

然后你可以这样称呼它：

public async Task<IEnumerable<User>> getUsers()
{
    return await getAsync("api/User");
}

public async Task<IEnumerable<permission>> getPermission()
{
    return await getAsync("api/User");
}

public async Task<CurrentUser> getCurrentUserInfo(User user)
{
    return await getAsync("api/User?name=" + user.Name);
}

如何将这些代码更改为c＃样式？

2 个答案: