Question

我正在函数中进行api调用，并在该函数中更新类变量（名称）的值。现在，当我检查该变量的值时，就可以了。但是，当我尝试在同一类中的其他任何地方访问它时，它什么也没有返回。我已经尝试了所有可能的解决方案。这是代码。

private void PopulateName()
        {
            try
            {
                string data1 = WebOp.baseUrl1 + "" + Const.action + "=" + Const.productByCategory + "" +
                 "&" + Const.category_id + "=" + category_id;


                System.Threading.Tasks.Task.Run(() =>
                {

                    RunOnUiThread(() => { progressDialog.Show(); });

                    WebOp webOp = new WebOp();
                    String str = webOp.doPost1(data1, this);

                    JObject jobj = JObject.Parse(str);


                    string status = jobj[Const.status].ToString();

                    if (status.Equals(Const.success))
                    {
                        try
                        {
                            string data = jobj[Const.data].ToString();
                            myDto = JsonConvert.DeserializeObject<List<ProductDto>>(data)[0];
                            name = myDto.thecategory_name;
                            Console.WriteLine("Check value:" + name); //returns the value fine
                            RunOnUiThread(() =>
                            {

                                progressDialog.Dismiss();
                            });
                        }
                        catch (Exception e)
                        {
                            Console.WriteLine(e + "");
                            RunOnUiThread(() => { progressDialog.Dismiss(); });
                        }
                    }
                    else
                    {
                        RunOnUiThread(() =>
                        {
                            progressDialog.Dismiss();
                        });
                    }


                }).ConfigureAwait(false);
            }
            catch (Exception e1)
            {
                Console.WriteLine(e1 + "");
            }
            Console.WriteLine("Check again:" + name); //returns nothing
        }

Answer 1

如果您希望任务在后台运行并仅在任务完成后才打印“名称”的值，则最佳选择是使用“异步..等待”。为此，请使您的方法异步并明确等待任务：

    // declare the method as Async using a return type of 'Task'
    private async Task PopulateName()
    {
        try
        {
            string data1 = WebOp.baseUrl1 + "" + Const.action + "=" + Const.productByCategory + "" +
             "&" + Const.category_id + "=" + category_id;

            // explicitly await the Task...
            await System.Threading.Tasks.Task.Run(() =>
            {

                RunOnUiThread(() => { progressDialog.Show(); });

                WebOp webOp = new WebOp();
                String str = webOp.doPost1(data1, this);

                JObject jobj = JObject.Parse(str);


                string status = jobj[Const.status].ToString();

                if (status.Equals(Const.success))
                {
                    try
                    {
                        string data = jobj[Const.data].ToString();
                        myDto = JsonConvert.DeserializeObject<List<ProductDto>>(data)[0];
                        name = myDto.thecategory_name;
                        Console.WriteLine("Check value:" + name); //returns the value fine
                        RunOnUiThread(() =>
                        {

                            progressDialog.Dismiss();
                        });
                    }
                    catch (Exception e)
                    {
                        Console.WriteLine(e + "");
                        RunOnUiThread(() => { progressDialog.Dismiss(); });
                    }
                }
                else
                {
                    RunOnUiThread(() =>
                    {
                        progressDialog.Dismiss();
                    });
                }


            }).ConfigureAwait(false);
        }
        catch (Exception e1)
        {
            Console.WriteLine(e1 + "");
        }
        Console.WriteLine("Check again:" + name); //returns nothing
    }

访问时，类变量的值始终为null

1 个答案: