Dumping a DB table to a flat file in C# efficiency issue

Question

I am having issues with efficiency when dumping a flat file using C# instead of SSIS. All that I'm doing is dumping a database table (SqlServer) of about 100k rows to a text file. Using SSIS this takes less than one second and using the C# code below takes over a minute which is unacceptable. What am I doing wrong?:

while (Reader.Read())
{
    foreach (string ColumnName in cols)
    {
        sb.Append('"' + Reader[ColumnName].ToString() + "\","); 
    }

    //save lines to file
    WriteLineToFile(TableDefinition.GetTableName(), sb.ToString());

    sb.Clear();
}

notes: sb variable is StringBuilder. This code dumps multiple tables hence the Reader.Read() on the while loop. The query is essentially a select * from tablename for each table in a list

WriteLineToFile method:

public static void WriteLineToFile(string TableName, string Text)
{
    System.IO.File.AppendAllText(OutputDir + @"\" + TableName + ".dat", Text + "\r\n");
}

Answer 1

In a nutshell SSIS most likely performs bulk operations for database read and export (more details here: SQL Server Bulk Operations) and your application writes to file one line at a time which is significantly less efficient.

You have not posted your C# code that reads from database so I can't comment on that but there may be similar inefficiency there as well.