c# 退出应用时进程不关闭问题

摘要问题描述

原理介绍

代码实例

摘要/问题描述

在写上位机过程中需要写一个UDP持续监听的功能，实现方式选择新建while循环进程的方法。但是调试过程中发现，关闭界面后，线程还在后台持续运行。经查询资料，最终选择Thread的IsBackground属性来实现应用退出时自动结束线程。

原理介绍

线程开启后默认为前台线程，如果关闭应用，此线程不会关闭，会在系统持续运行直到此线程运行结束（本例中需要持续监听，所以线程开启了while(true)无限循环，如果主应用不abort，线程自己不会结束）。设置IsBackground属性为true后，关闭应用，此线程自动终止。

代码实例

由于项目很大，在此只贴出能够展现此博文表述问题的代码块。

// This constructor arbitrarily assigns the local port number.
UdpClient udpClient = null;
Thread thread;

private void BUTTudpConnect_Click(object sender, EventArgs e)
{
if (BUTTudpConnect.Text == "connect")
{
udpClient = new UdpClient(Convert.ToInt32(TBLocalPort.Text));

try
{
udpClient.Connect(TBRemoteIP.Text, Convert.ToInt32(TBRemotePort.Text));
UdpSend( udpClient);
thread = new Thread(UdpListing);
thread.Start(udpClient);
thread.IsBackground = true;

}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
BUTTudpConnect.Text = "disconnect";
}
else
{
thread.Abort();
BUTTudpConnect.Text = "connect";
udpClient.Close();
}
}

private void UdpListing(Object obj)
{
UdpClient udpClient;
udpClient = (UdpClient)obj;

//IPEndPoint object will allow us to read datagrams sent from any source.
IPEndPoint RemoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);
while(true)
{
// Blocks until a message returns on this socket from a remote host.
Byte[] receiveBytes = udpClient.Receive(ref RemoteIpEndPoint);
string returnData = Encoding.ASCII.GetString(receiveBytes);

// Uses the IPEndPoint object to determine which of these two hosts responded.
MessageBox.Show("This is the message you received " +
returnData.ToString());
}
}