如何实现异步任务以使用异步和等待从数据库中获取数据？

Question

I am doing this. It's working but is this a recommended way to do this. Please comments

public async void LoadData()
{
    DataTable  dtAdditionsDetails = await LoadReportData(importID,
                                             InkeyCommon.ToInt32(cmbSellers.SelectedValue),
                                             fromDate,
                                             toDate);
    if (dtAdditionsDetails != null)
      dtaGrdAdditions.ItemSource = dtAdditionsDetails.DefaultView;
} 

public async Task<DataTable> LoadReportData(int? importID,
                                        int sellerID,
                                        DateTime? fromDate,
                                        DateTime? toDate)
{
    DataTable dtAdditionsDetails = new DataTable();

    //Get Report Data                                             
    await Task.Delay(1);

    dtAdditionsDetails = ReportsData.GetRptAdditions(importID,
                                  sellerID,
                                  fromDate,
                                  toDate);

    return dtAdditionsDetails;
}

Answer 1

In order to use the await keyword properly, the object being 'awaited' should really be an ...Async method, like the GetStringAsync method. As @ken2k has correctly pointed out, you cannot just await any method. Therefore, to answer your question is this a recommended way to do this? , the answer is no.

You can find out how to use the await and async keywords correctly in the Asynchronous Programming with Async and Await (C# and Visual Basic) page on MSDN, however, if you're just trying to run a synchronous method asynchronously, then you can do that like this:

public DataTable LoadData()
{
    DataTable dtAdditionsDetails = ...
    // Get your data here synchronously
    return dtAdditionsDetails;
} 

public async Task<DataTable> LoadDataAsync()
{
    DataTable dtAdditionsDetails = LoadData();
    return Task.Run(() => LoadData());
} 

...

public async void GetDataAsynchronously()
{
    DataTable dtAdditionsDetails = await LoadDataAsync();
} 

Note that ...Async methods (usually) return Task<T> objects, rather than nothing and that their names end in the word Async . Also note that only the data is returned from ...Async methods and not the Task<T> and that we don't await when there is nothing to await .

Answer 2

Here's a simple function, to load a list of all [User] records from a database, using async and await .

[HttpGet]
public async Task<IActionResult> Get()
{
    try
    {
        //  Fetch a list of all the [User] records, just for the hell of it.
        var users = await Task.Run(() => dbContextWebMgt.Users.ToList());
        return new OkObjectResult(users);
    }
    catch (Exception ex)
    {
        return new BadRequestObjectResult(ex.Message);
    }
}

Answer 3

You can try like this using NPoco ORM

[HttpGet]
public async Task<IActionResult> GetAsync()

{
      IList myList = await FetchAsync();
}