正确创建登录功能任务

Question

我正在编写我的windows窗体程序，我看到登录功能(链接到一个简单的按钮)冻结了我的应用程序。我在网上搜索，我发现如何创建一个任务，但我不确定它是如何工作的…

这是我的登录功能，我怎么才能正确地把它转换成任务?

string sURL = url + "/login";
string result = null;
await Task.Run(() =>
{
try
{
result = Web_api.MakeRequest("POST", sURL); //return null if there is some error
}
catch(Exception ex)
{
Debug.WriteLine("[frmLogin] --> result: " + result);
}
});
if(result != null)
{
try
{
Login_response accepted = JsonConvert.DeserializeObject<Login_response>(result);
Debug.WriteLine("[frm_Login] --> accepted: " + accepted);
if (accepted.login)
{
//throw new Exception();  
Debug.WriteLine("[frm_login]: result " + result);
frmMain frm = new frmMain();                             //calling the new form
frm.Show();                                              //new form is show-up
this.Hide();                                             //log-in form hide
frm.FormClosed += Frm_FormClosed;                        //close the form
}
}
//if server is down, or the id or password is wrong 
catch (Exception ex)
{
lblLoginError.Visible = true;                            //pop-up the error label
pbLogin.Visible = false;                                 //hide the progress-bar
this.Style = MetroFramework.MetroColorStyle.Red;         //changing the color of the form
Debug.WriteLine("Exception: " + ex);
}
}
else
{
lblLoginError.Visible = true;                            //pop-up the error label
pbLogin.Visible = false;                                 //hide the progress-bar
this.Style = MetroFramework.MetroColorStyle.Red;         //changing the color of the form
}

编辑:我提供了一个真实的(和工作的)解决方案，我遵循了评论中的所有建议…你觉得这样可以接受吗?

Answer 1

使用Task:

在后台线程上执行任何可能长时间运行的代码

private async void btnLogin_Click(object sender, EventArgs e)
{
if (string.IsNullOrEmpty(txtUser.Text.Trim()) || string.IsNullOrEmpty(txtPassword.Text.Trim()))
{
MessageBox.Show("You must insert a valid user/password format", "Login Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
return;
}
//Progress bar start
pbLogin.Visible = true; // BUT THIS PROGRESS BAR I STACK DUE TO STATIC DEFINITON OF LOGIN
//Getting ID + Password
User.username = txtUser.Text;
User.password = txtPassword.Text;
string sURL = Web_api.url + "/login";
try
{
Login_response accepted = await Task.Run(() =>
{
//the following code gets executed on a background thread...
string result = Web_api.MakeRequest("POST", sURL);
Login_response accepted = JsonConvert.DeserializeObject<Login_response>(result);
Debug.WriteLine("[frm_Login] --> accepted: " + accepted);
return accepted;
});

//...and here you are back on the UI thread once the task has completed
if (accepted.login)
{
//throw new Exception();  
Debug.WriteLine("[frm_login]: result " + result);
frmMain frm = new frmMain();                             //calling the new form
frm.Show();                                              //new form is show-up
this.Hide();                                             //log-in form hide
frm.FormClosed += Frm_FormClosed;                        //close the form
}
}
//if server is down, or the id or password is wrong 
catch (Exception ex)
{
lblLoginError.Visible = true;                            //pop-up the error label
pbLogin.Visible = false;                                 //hide the progress-bar
this.Style = MetroFramework.MetroColorStyle.Red;         //changing the color of the form
Debug.WriteLine("Exception: " + ex);
}
}

事件处理程序总是返回void。它们是异步方法总是应该返回Task或Task<T>的规则的一个例外。

Answer 2

可以创建一个async void方法。这实际上是实现诸如button click等事件的异步回调的正确方法。

首先，让我们创建一个异步登录方法:

public async Task LoginAsync()
{
try
{
var stream = await _http.GetStreamAsync($"{baseUrl}/login");
var response = await JsonSerializer.DeserializeAsync<LoginResponse>(stream);
if (!response.login)
{
throw new BusinessException<LoginError>(LoginError.LoginDenied);
}
}
catch (HttpRequestException ex)
{
throw new BusinessException<LoginError>(LoginError.LoginFailed, ex);
}
}

现在我们实现一个异步按钮回调:

private async void btnLogin_Click(object sender, EventArgs e)
{
try
{
await authentication.LoginAsync().ConfigureAwait(false);
// handle login success here
}
catch (BusinessException<LoginError> ex) when (ex.Error == LoginError.LoginDenied)
{
// handle login denied here
}
catch (BusinessException<LoginError> ex) when (ex.Error == LoginError.LoginFailed)
{
// handle connection failed here
}
}

如果你想让LoginAsync()方法做一些UI操作(例如显示表单)，你将需要使用ConfigureAwait(true)。否则，存在方法的一部分在另一个线程上执行的风险，UI操作将失败。