C# 线程池使用

使用C#线程池可以省去对线程的创建、销毁等操作，但是也不能很好的控制线程，这里是本人对线程池的理解，留下记录方便以后查询!

本DEMO用线程池多线程去读取Northwind所有表的数据与不用线程读取的时间差异

不用线程读取时间：

使用线程读取时间：

主要代码：

 1 不使用线程读取代码：

        private void button4_Click(object sender, EventArgs e)
        {
            if (listBox1.Items.Count > 0)
            {
                System.Diagnostics.Stopwatch singleThreadWatch = new System.Diagnostics.Stopwatch();
                singleThreadWatch.Start();
                tableCount = 0;
                useTime = 0;
                label1.Text = "";
                tabControl1.Controls.Clear();
                string[] list = new string[listBox1.Items.Count];
                for (int i = 0; i < listBox1.Items.Count; i++)
                {
                    list[i] = listBox1.Items[i].ToString();
                }

                if (list != null && list.Length > 0)
                {
                    foreach (string item in list)
                    {
                        tableCount += 1;

                        using (SqlConnection con = new SqlConnection(connectionString))
                        {
                            if (con.State != ConnectionState.Open) con.Open();
                            string selectAllTableNameSQL = "select * from [" + item.ToString()+"]";
                            using (SqlCommand sqlCmd = new SqlCommand(selectAllTableNameSQL, con))
                            {
                                sqlCmd.CommandType = CommandType.Text;
                                SqlDataReader sqlDataRead = sqlCmd.ExecuteReader();
                                if (null != sqlDataRead)
                                {
                                    DataTable dt = new DataTable();
                                    dt.Load(sqlDataRead);
                                    if (null != dt && dt.Rows.Count > 0)
                                    {
                                        DataGridView dgv = new DataGridView();
                                        dgv.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
                                        dgv.Dock = System.Windows.Forms.DockStyle.Fill;
                                        dgv.Location = new System.Drawing.Point(3, 3);
                                        dgv.Name = "dataGridView" + item.ToString();
                                        dgv.RowTemplate.Height = 23;

                                        dgv.DataSource = dt;

                                        TabPage tb = new TabPage();
                                        tb.Controls.Add(dgv);
                                        tb.Location = new System.Drawing.Point(4, 22);
                                        tb.Name = "tabPage" + item.ToString();
                                        tb.Padding = new System.Windows.Forms.Padding(3);
                                        tb.Size = new System.Drawing.Size(358, 446);
                                        tb.Text = "tabPage" + item.ToString();
                                        tb.UseVisualStyleBackColor = true;

                                        tabControl1.Controls.Add(tb);
                                        Application.DoEvents();
                                    }
                                }
                                sqlDataRead.Close();
                                sqlDataRead.Dispose();
                            }


                        }
                        Application.DoEvents();
                    }
                }


                singleThreadWatch.Stop();

                TimeSpan ts = singleThreadWatch.Elapsed;

                label1.Text = "单线程 表数量：" + list.Length.ToString() + " 总用时间: " + ts.TotalMilliseconds.ToString();

                
            }
        }

2 使用线程池读取代码：

        private void button3_Click(object sender, EventArgs e)
        {
            if (listBox1.Items.Count > 0)
            {
                tableCount = 0;
                useTime = 0;
                label1.Text = "";
                tabControl1.Controls.Clear();
                string[] list = new string[listBox1.Items.Count];

                for (int i = 0; i < listBox1.Items.Count; i++)
                {
                    list[i] = listBox1.Items[i].ToString();
                }

                ThreadSart(list);
            }
        }

        private void ThreadSart(object t)
        {
            string[] objs = t as string[];
            if (objs != null && objs.Length > 0)
            {
                foreach (string item in objs)
                {
                    tableCount += 1;
                  
                    ThreadPool.QueueUserWorkItem(new WaitCallback(OpenAllTables), item);
                    Application.DoEvents();
                }
            }

        }

       public void OpenAllTables(object obj)
        {
            OpenDBTables(obj.ToString());
        }

        private void OpenDBTables(string b)
        {
            System.Diagnostics.Stopwatch stopWatch = new System.Diagnostics.Stopwatch();
            stopWatch.Start();
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                if (con.State != ConnectionState.Open) con.Open();
                string selectAllTableNameSQL = "select * from [" + b.ToString()+"]";
                using (SqlCommand sqlCmd = new SqlCommand(selectAllTableNameSQL, con))
                {
                    sqlCmd.CommandType = CommandType.Text;
                    SqlDataReader sqlDataRead = sqlCmd.ExecuteReader();
                    if (null != sqlDataRead)
                    {
                        DataTable dt = new DataTable();
                        dt.Load(sqlDataRead);
                        if (null != dt && dt.Rows.Count > 0)
                        {
                            setData(dt,b);
                        }
                    }
                    sqlDataRead.Close();
                    sqlDataRead.Dispose();
                }


            }
            stopWatch.Stop();

            TimeSpan ts = stopWatch.Elapsed;
            Write(b.ToString() + " 打开用时：" + ts.TotalMilliseconds.ToString());

            useTime += ts.TotalMilliseconds;

            ShowCountAndTime();
            Application.DoEvents();

            //int MaxWorkerThreads, miot, AvailableWorkerThreads, aiot;

            ////获得最大的线程数量  
            //ThreadPool.GetMaxThreads(out MaxWorkerThreads, out miot);

            //AvailableWorkerThreads = aiot = 0;

            ////获得可用的线程数量  
            //ThreadPool.GetAvailableThreads(out AvailableWorkerThreads, out aiot);

            ////返回线程池中活动的线程数  
            //Write("活动的线程数:" + (MaxWorkerThreads - AvailableWorkerThreads).ToString());
        }