WPF 中加载文件的异步等待任务错误

Question

I am trying to do an async operation in UploadBtnExecute method.I am working this on wpf. But it shows some error.

error are:- error 1::-'

Task UploadBtnExecute(object)' has the wrong return type

error 2::- '

bool' does not contain a definition for 'GetAwaiter' and no accessible extension method 'GetAwaiter' accepting a first argument of type 'bool' could be found (are you missing a using directive or an assembly reference?)

What I have tried:

button click event to trigger a function

UploadBtnClick = new RelayCommands(UploadBtnExecute,UploadBtnCanExecuteUpload);

public async Task UploadBtnExecute(object param)
{
    Progress windowShow = new Progress();
    windowShow.Show();
    await UploadFiles();
    windowShow.Hide();
}

public bool UploadFiles(List<Item> selectedFiles)
{
    //do some upload code here
    return true;
}

Answer 1

Error 1:

An event handler must return void . This is this case where using async void instead of using async Task is recommended (mainly because there is no alternative, actually) for an async function that doesn't return a value.

Error 2:

Your second UploadFiles must return a Task<bool> instead of bool for await to make any sense.

Additionally, since this is the function actually doing something asynchronous, you probably wait it to be async Task<bool> and use await on the actual code that uploads something, but that may depend on your actual goal.

So as a summary, your snippet of code should be adapted like that:

UploadBtnClick = new RelayCommands(UploadBtnExecute,UploadBtnCanExecuteUpload);

public async void UploadBtnExecute(object param)
{
    Progress windowShow = new Progress();
    windowShow.Show();
    await UploadFiles();
    windowShow.Hide();
}

public async Task<bool> UploadFiles(List<Item> selectedFiles)
{
    // do some upload code here
    // using await ....
    return true;
}

// alternatively:
public Task<bool> UploadFiles(List<Item> selectedFiles)
{
    // do some upload code here
    return Task.FromResult(true);
}