DataReader.GetString() via columnname

Question

Dictionary Fields = new Dictionary();
for (int i = 0; i < reader.FieldCount; i++)
{
     Fields.Add(reader.GetName(i), i);
}

this._MyField1 = reader.GetString(Fields["field1"]);
this._Myfield2 = reader.GetInt16(Fields["field2"]);

doing this makes me want to cry but i can't seem to figure out how to use the type specfic retrieval methods by column name other than this way. please tell me there is a better way. this is specificly for DB2 but i would like the solution to work for MS Sql also if possible

Answer 1

Using SqlDataReader from Assembly System.Data.SqlClient, you can do the following (example):

List<string> list = new();
string query = "SELECT * FROM [YourTable]";
using SqlConnection conn = new(YourConnectionString);
using SqlCommand cmd = new(query, conn);
conn.Open();
using SqlDataReader reader = cmd.ExecuteReader();
while(reader.Read() && reader.HasRows)
{
    int columnNumber = reader.GetOrdinal("ColumnName")
    list.Add(reader.GetString(columnNumber));
}

The method GetOrdinal(string) from the object SqlDataReader, accept the column name you desire to get and return the column number. That number can be use for the method GetString(int)

Answer 2

You're looking for the GetOrdinal method:

this._MyField1 = reader.GetString(dr.GetOrdinal("field1"));
this._Myfield2 = reader.GetInt16(dr.GetOrdinal("field2"));

I generally cache the ordinals in an anonymous type for performance and readability:

// ...
using (IDataReader dr = cmd.ExecuteReader())
{
    var ordinals = new {
                           Foo = dr.GetOrdinal("Foo"),
                           Bar = dr.GetOrdinal("Bar")
                       };

    while (dr.Read())
    {
        DoSomething(dr.GetString(ordinals.Foo), dr.GetInt16(ordinals.Bar));
    }
}
// ...