Question

我有一个每次执行一个任务的列表，我的问题是当当前任务失败时如何停止待处理的任务？

这是我的代码：

if(await App.TodoManager.CheckContactsData(host, database, domain, contact) != 'failed)'{
     if(await App.TodoManager.CheckRetailerOutletData(contact)){
            //And so on
     }
}

我要执行的操作是想添加某种检查任务是否已成功执行的方法：

if(await App.TodoManager.CheckContactsData(host, database, domain, contact) == "ok"){
    //execute another task then check again if the task ok then proceed until the end of the task
}

这是我的示例任务，当重试变量等于FALSE时，不应执行挂起的任务：

public async Task CheckContactsData(string contact)
{
    try
    {
        var getcontactschanges = Constants.conn.QueryAsync<ContactsTable>("SELECT * FROM tblContacts WHERE Supervisor = ? AND LastUpdated > LastSync AND Deleted != '1'", contact);
        var contactchangesresultCount = getcontactschanges.Result.Count;

        Preferences.Set("contactschanges", contactchangesresultCount.ToString(), "private_prefs");
    }
    catch (Exception ex)
    {
        Crashes.TrackError(ex);
        var retry = await App.Current.MainPage.DisplayAlert("Checking Retailer Error", "Checking retailer failed.\n\nDo you want to retry? \n\n Error:\n\n" + ex.Message, "Yes", "No");

        if (retry)
        {
            await CheckContactsData(contact);
        }
        else {
            //Pending task should be stop
        }
    }
}

Answer 1

您可以通过这种方式

//for Task cancellation
var tokenSource = new CancellationTokenSource();

await App.TodoManager.CheckContactsData(host, database, domain, contact,tokenSource);
await App.TodoManager.CheckRetailerOutletData(contact,tokenSource);
await App.TodoManager.CheckCAFData(contact,tokenSource);
await App.TodoManager.CheckCAFActivityData(contact,tokenSource);
await App.TodoManager.CheckEmailRecipientData(contact,tokenSource);

您必须在每种方法中添加一个类型为CancellationTokenSource的新参数。

public async Task CheckContactsData(string contact,CancellationTokenSource cts)
{
    try
    {
        var getcontactschanges = Constants.conn.QueryAsync<ContactsTable>("SELECT * FROM tblContacts WHERE Supervisor = ? AND LastUpdated > LastSync AND Deleted != '1'", contact);
        var contactchangesresultCount = getcontactschanges.Result.Count;

        Preferences.Set("contactschanges", contactchangesresultCount.ToString(), "private_prefs");
    }
    catch (Exception ex)
    {
        cts.Cancle();
        Crashes.TrackError(ex);
        var retry = await App.Current.MainPage.DisplayAlert("Checking Retailer Error", "Checking retailer failed.\n\nDo you want to retry? \n\n Error:\n\n" + ex.Message, "Yes", "No");

        if (retry)
        {
            await CheckContactsData(contact);
        }
        else {
            //Pending task should be stop
        }
    }
}

然后，您必须在每个cts.Cancle();中致电catch，

然后您可以像检查

if(!tokenSource.Token.IsCancellationRequested){
    //execute another task then check again if the task ok then proceed until the end of the task
}

我希望这会对您有所帮助。

当前任务失败时如何停止待执行的任务？

1 个答案: