考慮,2個按鈕的表單和一個RichTextBox:與Task.Run有什麼區別,void方法和Task方法返回null?
public partial class MainForm : Form
{
CancellationTokenSource cts;
CancellationToken token;
public MainForm()
{
InitializeComponent();
}
private void MainForm_Load(object sender, EventArgs e)
{
cts = new CancellationTokenSource();
token = cts.Token;
var task = Task.Run(() => WriteSomeLines(), token);
}
private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
{
cts.Dispose();
}
private void btnStart_Click(object sender, EventArgs e)
{
cts = new CancellationTokenSource();
token = cts.Token;
var task = Task.Run(() => WriteSomeLines(), token);
}
private void btnCancel_Click(object sender, EventArgs e)
{
try
{
cts.Cancel();
cts.Dispose();
}
catch (ObjectDisposedException exc)
{
MessageBox.Show(exc.GetType().Name);
//object disposed
}
}
public void WriteSomeLines()
{
if (ControlInvokeRequired(rtbLoops,() => rtbLoops.Text += "Starting new loop \r\n")) ;
else rtbLoops.Text += "Starting new loop \r\n";
for (int i = 0; i < 30; i++)
{
try
{
if (ControlInvokeRequired(rtbLoops,() => { rtbLoops.AppendText("New line " + i + "\r\n"); rtbLoops.ScrollToCaret(); })) ;
else rtbLoops.AppendText("New line " + i + "\r\n");
Thread.Sleep(250);
token.ThrowIfCancellationRequested();
}
catch (OperationCanceledException ae)
{
MessageBox.Show(ae.GetType().Name);
return;
}
}
return;
}
public bool ControlInvokeRequired(Control c, Action a)
{
if (c.InvokeRequired)
c.Invoke(new MethodInvoker(delegate { a(); }));
else
return false;
return true;
}
}
是否有區別,如果WriteSomeLines()
是返回void我用回裏面,或者如果WriteSomeLines()
返回的任務,我也返回null呢?我看,我不能空回來方法使用await
,但是任務宣佈後插入
await task;
(在上面的代碼)編譯完全正常,並沒有問題運行。
編輯:
private async void btnStart_Click(object sender, EventArgs e)
{
cts = new CancellationTokenSource();
token = cts.Token;
var task = Task.Run(() => WriteSomeLines(), token);
await task;
rtbLoops.Text += "Task complete";
}
這將編譯沒有問題,如果WriteSomeLines()
返回void。
此外,稍微未實現,我在這裏正確地處置CancellationTokenSource
?
第二個編輯:
因此,這是正確的做法:
private async void btnStart_Click(object sender, EventArgs e)
{
cts.Dispose();
cts = new CancellationTokenSource();
token = cts.Token;
var task = Task.Run(() => WriteSomeLines(), token);
bool result = await task;
if(result == true) rtbLoops.Text += "Task complete \r\n";
}
和
public async Task<bool> WriteSomeLines()
{
if (ControlInvokeRequired(rtbLoops,() => rtbLoops.Text += "Starting new loop \r\n")) ;
else rtbLoops.Text += "Starting new loop \r\n";
for (int i = 0; i < 30; i++)
{
try
{
if (ControlInvokeRequired(rtbLoops,() => { rtbLoops.AppendText("New line " + i + "\r\n"); rtbLoops.ScrollToCaret(); })) ;
else rtbLoops.AppendText("New line " + i + "\r\n");
await Task.Delay(250);
token.ThrowIfCancellationRequested();
}
catch (OperationCanceledException ae)
{
MessageBox.Show(ae.GetType().Name);
return false;
}
}
return true;