c# - C# 中的数据网格访问

Question

我是 c# 和 Database 链接的新手，这就是为什么无法通过搜索 stackoverflow 的旧帖子来获得它的原因

代码如下

private void issueDetails()
    {
        string connectionPath = @"Data Source=Data\libraryData.dat;Version=3;New=False;Compress=True";

        using (SQLiteConnection connection = new SQLiteConnection(connectionPath))
        {
            SQLiteCommand command = connection.CreateCommand();
            connection.Open();
            string query = "SELECT bookno as 'Book No.',studentId as 'Student ID',  title as 'Title', author as 'Author', description as 'Description', issuedDate as 'Issued Date', dueDate as 'Due Date' FROM issuedBooks";
            command.CommandText = query;
            command.ExecuteNonQuery();

            SQLiteDataAdapter da = new SQLiteDataAdapter(command);
            DataSet ds = new DataSet();
            da.Fill(ds, "issuedBooks");
            dataGridView1.DataSource = ds.Tables["issuedBooks"];
            dataGridView1.Sort(dataGridView1.Columns["Student ID"], ListSortDirection.Ascending);
            dataGridView1.ReadOnly = true;
            connection.Close();
        }
    }

我像上面那样使用来获取一些图书馆书籍的详细信息，例如 issuedDate 和 dueDate，现在我想突出显示超过 dueDate 的特定单元格。

private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
    {
        Color c = Color.Black;
        if (e.ColumnIndex == 6)
        {
            if (isLate(Convert.ToString(e.Value)))
            {
                c = Color.Red;
                count++;
                Console.WriteLine(count);
            }

        }
        e.CellStyle.ForeColor = c;
    }

    public string toInd(string date)
    {
        DateTimeFormatInfo fmt = new CultureInfo("fr-fr").DateTimeFormat;
        string dateString;
        DateTimeOffset offsetDate, dateig;
        string ret = DateTime.Now.ToShortDateString();
        dateString = date;
        bool ws = DateTimeOffset.TryParse(dateString, fmt, DateTimeStyles.None, out dateig);
        if (ws)
        {
            offsetDate = DateTimeOffset.Parse(dateString, fmt);
            ret = offsetDate.Date.ToShortDateString();
            return ret;
        }
        return ret;
    }

    private bool isLate(string nowS)
    {

        DateTime dueDate = Convert.ToDateTime(toInd(nowS));
        DateTime now;
        string present = DateTime.Now.ToShortDateString();
        now = Convert.ToDateTime(present);
        //Console.WriteLine(toInd(nowS));
        int a = dueDate.CompareTo(now);
        if (a >= 0)
            return false;
        else return true;
    }

但如果使用 if (isLate(Convert.ToString(e.Value)))
{
c = 颜色.红色;
计数++；
控制台.WriteLine(计数);
} 这对于逾期图书的数量，即使我的数据库中只有两本书逾期，'count' 值也会增加 4 次，因为如果在数据绑定(bind)时阻止访问 2 次，并且在排序时再次阻止访问两次怎么能我只得到超过到期账面值(value)的数字

Answer 1

实际上，dataGridView1_CellFormatting 会在每个单元格事件上触发，包括您是否排序，或者即使您将鼠标悬停在单元格上......在性能方面非常昂贵。

相反，您可以在 dgv 上使用 RowsAdded 事件，它只会在添加时触发一次:

    private void dataGridView1_RowsAdded(object sender, DataGridViewRowsAddedEventArgs e)
    {
        if (isLate(dataGridView1[6, e.RowIndex].Value.ToString()))
        {
            dataGridView1[0, e.RowIndex].Style.ForeColor = Color.Red;
            count++;
        }
    }