Winforms: refreshing during loop

Question

I am looping through a dataset in c# read from an excel file that contains X records. For testing purposes, I used Thread.Sleep() to pause the output for a second after each record is read. My understanding was that they way I wrote my loop, it should pause for 1 second then display 1 line of output (1 record), pause for 1 second, display 1 line, etc... However, when I execute the code I get a X second long pause followed by all records immediately being output to screen. Anyone know why this is happening? I inserted a breakpoint and stepped through it and everything seems to be working fine (no errors or anything). Sorry if this is a basic question but I'm a bit of green programmer.

private void ReadExcelFile()
    {
        string fileAndPath = fileTextBox.Text;
        string fileName = Path.GetFileName(fileAndPath);
        string directoryPath = Path.GetDirectoryName(fileAndPath);

        var connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + fileAndPath + ";Extended Properties=\"Excel 12.0;IMEX=1;HDR=NO;TypeGuessRows=0;ImportMixedTypes=Text\""; ;
        using (var conn = new OleDbConnection(connectionString))
        {
            conn.Open();

            var sheets = conn.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Tables, new object[] { null, null, null, "TABLE" });
            using (var cmd = conn.CreateCommand())
            {
                cmd.CommandText = "SELECT * FROM [" + sheets.Rows[0]["TABLE_NAME"].ToString() + "] ";

                var adapter = new OleDbDataAdapter(cmd);
                var ds = new DataSet();
                adapter.Fill(ds);

                foreach (DataRow row in ds.Tables[0].Rows)
                {
                    user = row.ItemArray[0].ToString();
                    email = row.ItemArray[1].ToString();
                    password = row.ItemArray[2].ToString();
                    Thread.Sleep(1000);                   

                    excelTextBox.Text += user + "     " + email + "     " + password + "     " + Environment.NewLine;
                }                    
            }
        }
    }

Consider using '\t' instead of " " (multiple spaces). – Danny Varod Jan 21 '13 at 17:54 — Danny Varod, Jan 21 '13 at 17:54

score 3 · Accepted Answer · edited May 23 '17 at 10:34

3

Since you are running this method on the main thread (the UI's thread), the thread isn't available to process events (e.g. display updates).

You can do something similar to this to process UI messages: https://stackoverflow.com/a/3121934/38368

Or, better yet, redesign your code. E.g. use a separate thread. E.g. https://stackoverflow.com/a/1216799/38368

edited May 23 '17 at 10:34

Community

1
1

answered Jan 21 '13 at 17:23

Danny Varod

17,324
5
69
111

I won't be using threading in my live application, but your suggestions still work out with what I want to do. Thanks! – ovaltein Jan 21 '13 at 18:48

Winforms: refreshing during loop

1 Answers1