OdbcConnectionStringBuilder oCSB = new OdbcConnectionStringBuilder();
oCSB.Driver = "Microsoft Text Driver (*.txt; *.csv)";
oCSB.Add("DBQ", @"C:\");
oCSB.Add("Extensions", "asc,csv,tab,txt");

OdbcConnection oConn = new OdbcConnection(oCSB.ConnectionString);
oConn.Open();
            
using (OdbcCommand oCmd = new OdbcCommand(String.Format("SELECT * FROM {0}", "5.txt"), oConn))
using (OdbcDataReader oDR = oCmd.ExecuteReader())
using (SqlConnection connection = new SqlConnection(GetConnectionString()))
using (SqlBulkCopy bcp = new SqlBulkCopy(connection))
{
    connection.Open();
    bcp.DestinationTableName = "dbo.TBL_TEST5";
    //bcp.ColumnMappings.Add("FLD", "FLD");
    bcp.WriteToServer(oDR);
}

private DataTable CreateDataTableFromFile()
{
    DataTable dt = new DataTable();
    DataColumn dc = new DataColumn();
    DataRow dr;

    dc.DataType = typeof(int); // Type.GetType("System.Int32");
    dc.ColumnName = "FLD";
    dc.Unique = false;

    dt.Columns.Add(dc);

    using (StreamReader sr = new StreamReader(@"C:\test.txt"))
    {
        string input;
        while ((input = sr.ReadLine()) != null)
        {
            string[] s = input.Split(new char[] { '|' });
            dr = dt.NewRow();
            dr["FLD"] = s[0];
            dt.Rows.Add(dr);
        }
    }

    return dt;
}

using (SqlConnection connection = new SqlConnection(GetConnectionString()))
{
    connection.Open();                
    using (SqlBulkCopy bcp = new SqlBulkCopy(connection))
    {
        bcp.DestinationTableName = "dbo.TBL_TEST5";
        bcp.ColumnMappings.Add("FLD", "FLD");
        bcp.WriteToServer(CreateDataTableFromFile());
    }               
}