How to get only specified item of list? - mysql

Question

I extract the following data from database with the following MySql Query:
SELECT vs.value, vs.is_header, vsa.is_required, vsa.name, vsar.value
FROM vista_struttura AS vs
LEFT JOIN vista_struttura_attributi AS vsa
ON vs.id_vista_struttura = vsa.id_vista_struttura
LEFT JOIN vista_struttura_attributi_raccordi AS vsar
ON vsa.input_type = vsar.input_type
ORDER BY vs.sort;
Data extracted are
I have to save this data in a model built from myself with the following code:
var model = new List<Header>();
using (var connection = new MySqlConnection(connectionString))
{
connection.Open();
var sql = "SELECT vs.value, vs.is_header, vsa.is_required, vsa.name, vsar.value " +
"FROM vista_struttura AS vs " +
"LEFT JOIN vista_struttura_attributi AS vsa " +
"ON vs.id_vista_struttura = vsa.id_vista_struttura " +
"LEFT JOIN vista_struttura_attributi_raccordi AS vsar " +
"ON vsa.input_type = vsar.input_type " +
"ORDER BY vs.sort";
var cmd = new MySqlCommand(sql, connection);
var rdr = cmd.ExecuteReader();
var rows = new List<ViewProperties>();
while (rdr.Read())
{
var value = rdr[0].ToString();
var isHeader = Convert.ToBoolean(rdr[1]);
var isRequired = (rdr[2] == DBNull.Value) ? (bool?) null : Convert.ToBoolean(rdr[2]);
var name = rdr[3].ToString();
var inputType = rdr[4].ToString();
var properties = new ViewProperties()
{
Value = value,
IsHeader = isHeader,
IsRequired = isRequired,
Name = name,
InputType = inputType
};
rows.Add(properties);
var header = new Header()
{
HeaderValue = (properties.IsHeader == true) ? properties.Value : null,
Rows = rows
};
if (header.HeaderValue != null)
{
model.Add(header);
}
}
}
Models
Header
public class Header
{
public string HeaderValue { get; set; }
public IList<ViewProperties> Rows { get; set; }
}
ViewProperties
public class ViewProperties
{
public string Value { get; set; }
public bool IsHeader { get; set; }
public bool? IsRequired { get; set; }
public string Name { get; set; }
public string InputType { get; set; }
}
Debugging the app I get a wrong model, not such as I want...
I want to get first 4 rows for first header and the other last 3 rows for the second header.
How can i do?
What's better to do: before get this model and then handle it with linq, or get already correct model?
Thanks

Answer 1

You need the following code for the desired result, make the necessary modifications:
var rows = new List<ViewProperties>(); // ViewProperties List
// Segregate null value, GroupBy to aggregate using Value
var viewPropertiesGrouping = rows.Where(x => x.IsHeader)
.GroupBy(x => x.Value);
// Traverse through IEnumerable<IGrouping<string,ViewProperties>>, created above and fill the Header object and add to the Model
foreach (var prop in viewPropertiesGrouping)
{
Header header = new Header();
header.HeaderValue = prop.Key;
header.Rows = prop.Select(y => y).ToList();
model.Add(header);
}