如何使用帶有后臺作業人員的文本框textChanged屬性來填充datagridview

在我的表單中，我有一個文本框、后臺作業人員和一個資料網格視圖。使用文本框（TextChanged 屬性），我想使用后臺作業人員獲取資料，并在我鍵入時在資料網格視圖中填充匹配資料。

這是我嘗試過的。

 private void txtSearchBox_TextChanged(object sender, EventArgs e)
 {
   if (backgroundWorker1.IsBusy)
   {
   backgroundWorker1.CancelAsync();
   }
   backgroundWorker1.RunWorkerAsync();///Runs the background worker     
 }

        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {                
                try
                {
                    con.Open();
                    MySqlDataAdapter da = new MySqlDataAdapter("select * from Games where Name like '%"   txtSearchBox.Text   "%'", con);
                    
                    da.Fill(ds, "GameID");                    
                    con.Close();
                }
                catch (Exception ex)
                {
                    MessageBox.Show("Error"   ex);
                }  
        }

        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            SimilarData.DataSource = ds.Tables["GameID"].DefaultView;
        }

有了這個錯誤。ErrorSystem.InvalidOperationExceptoin：此后臺作業人員當前很忙，并且沒有同時運行多個任務。

我該怎么辦？

uj5u.com熱心網友回復：

如果您愿意接受比使用BackgroundWorker我建議的更簡單的方法，那就是async為事件創建一個處理程式，該處理程式textbox.TextChanged在等待快速輸入的“冷卻”期之前記錄擊鍵計數。如果等待此延遲之前和之后的計數相同，則表明輸入足夠穩定以執行查詢。

sqlite-net-pcl為了方便起見，我已經使用它來嘲笑它。DGV 系結到 aDataSource即 a BindingList<Game>。的OnLoad覆寫MainForm初始化DataGridView，然后是您正在使用的任何資料庫服務器。最后一件事是訂閱TextChanged事件，這是所有動作發生的地方。

protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);
    initDGV();
    initSQL();
    textBox.TextChanged  = onTextBoxTextChanged;
}
BindingList<Game> DataSource = new BindingList<Game>();
// Comparing the awaited count to the total count so that
// the DGV isn't visually updated until all queries have run.
int _queryCount = 0;

TextBox.TextChanged事件處理程式（異步）

private async void onTextBoxTextChanged(object sender, EventArgs e)
{
    if(string.IsNullOrWhiteSpace(textBox.Text))
    {
        return;
    }
    _queryCount  ;
    var queryCountB4 = _queryCount;
    List<Game> recordset = null;
    var captureText = textBox.Text;

    // Settling time for rapid typing to cease.
    await Task.Delay(TimeSpan.FromMilliseconds(250));

    // If keypresses occur in rapid succession, only
    // respond to the latest one after a settling timeout.
    if (_queryCount.Equals(queryCountB4))
    {
        await Task.Run(() =>
        {
            using (var cnx = new SQLiteConnection(ConnectionString))
            {
                var sql = $"SELECT * FROM games WHERE GameID LIKE '{captureText}%'";
                recordset = cnx.Query<Game>(sql);
            }
        });
        DataSource.Clear();
        foreach (var game in recordset)
        {
            DataSource.Add(game);
        }
    }
    else Debug.WriteLine("Waiting for all pending queries to complete");
}

資料網格視圖

private void initDGV()
{
    dataGridView.DataSource = DataSource;
    dataGridView.AllowUserToAddRows = false;
    DataSource.Add(new Game { GameID = "Generate Columns" });
    dataGridView
        .Columns[nameof(Game.GameID)]
        .AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;
    dataGridView
        .Columns[nameof(Game.Created)]
        .AutoSizeMode = DataGridViewAutoSizeColumnMode.AllCells;
    DataSource.Clear();
}

資料庫

private void initSQL()
{
    // For testing, start from scratch every time
    if (File.Exists(ConnectionString)) File.Delete(ConnectionString);
    using (var cnx = new SQLiteConnection(ConnectionString))
    {
        cnx.CreateTable<Game>();
        cnx.Insert(new Game { GameID = "Awe" });
        cnx.Insert(new Game { GameID = "Abilities" });
        cnx.Insert(new Game { GameID = "Abscond" });
        cnx.Insert(new Game { GameID = "Absolve" });
        cnx.Insert(new Game { GameID = "Absolute" });
    }
}

游戲

[Table("games")]
class Game
{
    [PrimaryKey, Browsable(false)]
    public string Guid { get; set; } = System.Guid.NewGuid().ToString().ToUpper();
    public string GameID { get; set; }
    private DateTime _created = DateTime.Now.Date;
    public string Created 
    {
        get => _created.ToShortDateString();
        set
        {
            if(DateTime.TryParse(value, out DateTime dt))
            {
                _created = dt.Date;
            }
        }
    }
}

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