尽管有线程，但搜索数据库时 UI 性能缓慢

Question

我目前正在处理我的项目，而我一直面临的问题是当您在数据库中搜索数据时，性能会变慢并且没有响应。

我已经创建了一个线程，但它仍然让我头疼

//to start the thread when textbox has change
private void textBox1_TextChanged(object sender, EventArgs e)
{
    ThreadStart thread2Start = new ThreadStart(searchMyData);
    Thread t2 = new Thread(thread2Start);
    t2.Start();
}

public void searchMyData()
{
    if (radGridView1.InvokeRequired)
    {
        radGridView1.Invoke(new Action(() =>
        {
            MySqlConnection connection = new MySqlConnection(MyConnectionString);
            MySqlCommand cmd;
            connection.Open();

            try
            {
                if(!(textBox1.Text=="Search Students")) 
                { 
                    cmd = connection.CreateCommand();
                    cmd.CommandText = "SELECT * from studenttable where studname like'" + textBox1.Text + "%' OR studnum like'" + textBox1.Text + "%' OR studcourse like'" + textBox1.Text + "%' OR studemail like'" + textBox1.Text + "%' OR studsec like'" + textBox1.Text + "%' OR studgender like'" + textBox1.Text + "%' ";

                    MySqlDataAdapter adap = new MySqlDataAdapter(cmd);
                    DataSet ds = new DataSet();
                    adap.Fill(ds);
                    radGridView1.DataSource = ds.Tables[0].DefaultView;
                    connection.Close();
                }
            }
        }
    }
}

那么这里有什么解决方案可以提高我的程序的性能？

Answer 1

您正在 UI 线程中运行 searchMyData() 函数，这就是它缓慢的原因。尝试更新以下代码，

private void txtSearch_TextChanged(object sender, EventArgs e)
{
    if (txtSymbol.Text == "Search Students")
    {
        ParameterizedThreadStart pts = new ParameterizedThreadStart(searchMyData);
        Thread t = new Thread(pts);
        t.Start(txtSymbol.Text);
    }
 }

public void searchMyData(object state)
{
    try
    {
        string text = state.ToString();
        using (MySqlConnection connection = new MySqlConnection(MyConnectionString))
        {
            connection.Open();
            MySqlCommand cmd = connection.CreateCommand();
            cmd.CommandText = "SELECT * from studenttable where studname like'" + text + "%' OR studnum like'" + text + "%' OR studcourse like'" + text + "%' OR studemail like'" + text + "%' OR studsec like'" + text + "%' OR studgender like'" + text + "%' ";

            MySqlDataAdapter adap = new MySqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            adap.Fill(ds);
            radGridView1.Invoke(new Action(() => { radGridView1.DataSource = ds }));
        }
    }
    catch(Exception ex) { }
}

Answer 2

没有必要为这种事情引入显式线程。此代码中需要时间的操作是打开数据库连接并填充数据集。您可以轻松地使用任务和 async/await 在后台执行此操作。我认为 MySql 连接和适配器没有异步方法，因此您可能必须将它们包装在任务中，如下所示：

private void txtSearch_TextChanged(object sender, EventArgs e)
    {
        if (txtSymbol.Text == "Search Students")
        {
           radGridView1.DataSource = await SearchMyDataAsync(txtSymbol.Text);
        }
    }

    async Task<DataSet> SearchMyDataAsync(object state)
    {
        try
        {
            using (MySqlConnection connection = new MySqlConnection(MyConnectionString))
            {
                await Task.Run(() => connection.Open()); //Or possibly connection.OpenAsync() if it exists...
                MySqlCommand cmd = connection.CreateCommand();
                cmd.CommandText = "SELECT * from studenttable where studname like'" + text + "%' OR studnum like'" +
                                  text + "%' OR studcourse like'" + text + "%' OR studemail like'" + text +
                                  "%' OR studsec like'" + text + "%' OR studgender like'" + text + "%' ";

                MySqlDataAdapter adap = new MySqlDataAdapter(cmd);
                DataSet ds = new DataSet();
                await Task.Run(adap.Fill(ds));
                return ds;
            }
        }
        catch (Exception ex)
        {
            throw;
        }
    }

另外，请注意，当您从 UI 事件启动异步操作时，无论使用何种技术，都应该考虑可重入性。这里有一些关于堆栈溢出的好信息，但基本上，当用户快速连续键入一些字母时，您可能希望避免一次执行多个数据库查询。更多信息在这里：Reentrancy in async/await?