Question

我很难关注.NET Async / Await示例，例如官方的MDN教程。

从我收集的内容来看，要使控制器操作异步，我必须：

在方法名称前添加async。
在主要任务运行之前添加await。
如果我从商店或存储库中提取，则必须将Task.Run()添加到商店方法。
async方法必须返回Task<>

当我这样做时，编译器中没有错误或警告，该方法就会挂起。我哪里错了？

PostsController.cs

    public async Task<IHttpActionResult> Get()
    {
        PostsStore store = new PostsStore();
        List<Post> AsyncResult = await store.GetPosts();
        return Ok(AsyncResult);
    }

PostsStore.cs

    public async Task<List<Post>> GetPosts()
    {
         List<Post> result =  await Task.Run(() => {
            List<Post> posts = new List<Post>();
            string conn = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
            using (SqlConnection connection = new SqlConnection(conn))
            {
                SqlCommand command = new SqlCommand();
                command.Connection = connection;
                command.CommandText = "GetPosts";
                command.CommandType = System.Data.CommandType.StoredProcedure;

                connection.Open();
                SqlDataReader dr = command.ExecuteReader();
                while (dr.Read())
                {
                    Post post = new Post()
                    {
                        PostId = (int)(dr["PostId"]),
                        Title = dr.SafeGetString("Title"),
                        Body = dr.SafeGetString("Body"),
                        SaveTitle = dr.SafeGetString("SaveTitle"),
                        SaveBody = dr.SafeGetString("SaveBody"),
                        Slug = dr.SafeGetString("Slug"),
                        State = dr.SafeGetString("State"),
                        IsPublished = (bool)(dr["IsPublished"]),
                        LastSaved = (DateTime)(dr["LastSaved"]),
                        CreateDate = (DateTime)(dr["CreateDate"])
                    };
                    posts.Add(post);
                }
                dr.Close();
                connection.Close();
                return posts;
            }

        });

        return result;

    }

Answer 1

这里不需要Task.Run。您可以考虑重构该方法以利用可用的异步调用。

public class PostsStore {
    public async Task<List<Post>> GetPostsAsync() {
        var posts = new List<Post>();
        var connectionString = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
        using (var connection = new SqlConnection(connectionString)) {
            var command = new SqlCommand();
            command.Connection = connection;
            command.CommandText = "GetPosts";
            command.CommandType = System.Data.CommandType.StoredProcedure;

            await connection.OpenAsync();
            using (var reader = await command.ExecuteReaderAsync()) {
                while (await reader.ReadAsync()) {
                    var post = new Post() {
                        PostId = (int)(reader["PostId"]),
                        Title = reader.SafeGetString("Title"),
                        Body = reader.SafeGetString("Body"),
                        SaveTitle = reader.SafeGetString("SaveTitle"),
                        SaveBody = reader.SafeGetString("SaveBody"),
                        Slug = reader.SafeGetString("Slug"),
                        State = reader.SafeGetString("State"),
                        IsPublished = (bool)(reader["IsPublished"]),
                        LastSaved = (DateTime)(reader["LastSaved"]),
                        CreateDate = (DateTime)(reader["CreateDate"])
                    };
                    posts.Add(post);
                }
            }
        }
        return posts;
    }
}

注意更新方法名称以反映使用异步方法的命名约定

public async Task<IHttpActionResult> Get() {
    var store = new PostsStore();
    var posts = await store.GetPostsAsync();
    return Ok(posts);
}

现在开始考虑审查/重构上述课程，因为在那里可能会出现许多问题，这可能会使其在将来出现问题。

.NET WebApi异步控制器操作永远执行

1 个答案: