求简易的C#+SQL Server程序注释——请给我的程序写个注释，O(∩_∩)O谢谢！

public static DataTable ExecuteDataTable(string sql)
{
using (OleDbDataAdapter da = new OleDbDataAdapter(sql, connectionString))
{
DataSet ds = new DataSet();
da.Fill(ds);
return ds.Tables[0];
}
}

public static OleDbDataReader CreateReader(string sql)
{
using (OleDbConnection conn = new OleDbConnection(connectionString))
{
try
{
conn.Open();
OleDbCommand cmd = conn.CreateCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = sql;
OleDbDataReader Rs = cmd.ExecuteReader();
return Rs;
}
finally
{
if (conn.State == ConnectionState.Open) conn.Close();
}

}
}

public static void ExecuteNonQuery(string sql)
{
using (OleDbConnection conn = new OleDbConnection(connectionString))
{
try
{
conn.Open();

OleDbCommand cmd = conn.CreateCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = sql;
cmd.ExecuteNonQuery();
cmd.Dispose();
}
finally
{
if (conn.State == ConnectionState.Open) conn.Close();
}
}
}
}
}