private async void Button2_Click(object sender, EventArgs e)
{
OleDb.GetSheetsNames(excel);
var table = await Task.Run(() => OleDb.ReadData(excel, txtnmlst.Text));
dataGridView1.DataSource = excel.Data;
for (var i = 0; i < dataGridView1.Columns.Count; i++)
{
dataGridView1.Columns[i].HeaderCell.Style.BackColor = Color.Gray;
dataGridView1.Columns[i].HeaderCell.Style.ForeColor = Color.DarkGray;
}
for (var i = 0; i < dataGridView1.RowCount; i++)
{
dataGridView1.Rows[i].HeaderCell.Value = i.ToString();
}
lstColNames.Items.Clear();
foreach (DataColumn col in excel.Data.Columns)
{
lstColNames.Items.Add(col.ColumnName);
}
GC.Collect();
GC.WaitForPendingFinalizers();
}