How and when to use ‘async’ and ‘await’

Question

From my understanding one of the main things that async and await do is to make code easy to write and read - but is using them equal to spawning background threads to perfo

Answer 1

Below is code which reads excel file by opening dialog and then uses async and wait to run asynchronous the code which reads one by one line from excel and binds to grid

namespace EmailBillingRates
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            lblProcessing.Text = "";
        }

        private async void btnReadExcel_Click(object sender, EventArgs e)
        {
            string filename = OpenFileDialog();

            Microsoft.Office.Interop.Excel.Application xlApp = new Microsoft.Office.Interop.Excel.Application();
            Microsoft.Office.Interop.Excel.Workbook xlWorkbook = xlApp.Workbooks.Open(filename);
            Microsoft.Office.Interop.Excel._Worksheet xlWorksheet = xlWorkbook.Sheets[1];
            Microsoft.Office.Interop.Excel.Range xlRange = xlWorksheet.UsedRange;
            try
            {
                Task longRunningTask = BindGrid(xlRange);
                int result = await longRunningTask;

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
            }
            finally
            {
                //cleanup  
               // GC.Collect();
                //GC.WaitForPendingFinalizers();

                //rule of thumb for releasing com objects:  
                //  never use two dots, all COM objects must be referenced and released individually  
                //  ex: [somthing].[something].[something] is bad  

                //release com objects to fully kill excel process from running in the background  
                Marshal.ReleaseComObject(xlRange);
                Marshal.ReleaseComObject(xlWorksheet);

                //close and release  
                xlWorkbook.Close();
                Marshal.ReleaseComObject(xlWorkbook);

                //quit and release  
                xlApp.Quit();
                Marshal.ReleaseComObject(xlApp);
            }

        }

        private void btnSendEmail_Click(object sender, EventArgs e)
        {

        }

        private string OpenFileDialog()
        {
            string filename = "";
            OpenFileDialog fdlg = new OpenFileDialog();
            fdlg.Title = "Excel File Dialog";
            fdlg.InitialDirectory = @"c:\";
            fdlg.Filter = "All files (*.*)|*.*|All files (*.*)|*.*";
            fdlg.FilterIndex = 2;
            fdlg.RestoreDirectory = true;
            if (fdlg.ShowDialog() == DialogResult.OK)
            {
                filename = fdlg.FileName;
            }
            return filename;
        }

        private async Task BindGrid(Microsoft.Office.Interop.Excel.Range xlRange)
        {
            lblProcessing.Text = "Processing File.. Please wait";
            int rowCount = xlRange.Rows.Count;
            int colCount = xlRange.Columns.Count;

            // dt.Column = colCount;  
            dataGridView1.ColumnCount = colCount;
            dataGridView1.RowCount = rowCount;

            for (int i = 1; i <= rowCount; i++)
            {
                for (int j = 1; j <= colCount; j++)
                {
                    //write the value to the Grid  
                    if (xlRange.Cells[i, j] != null && xlRange.Cells[i, j].Value2 != null)
                    {
                         await Task.Delay(1);
                         dataGridView1.Rows[i - 1].Cells[j - 1].Value =  xlRange.Cells[i, j].Value2.ToString();
                    }

                }
            }
            lblProcessing.Text = "";
            return 0;
        }
    }

    internal class async
    {
    }
}