Accessing a variable using a string containing the variable's name [duplicate]

Do you mean you want to get the value of a field using the field name as a string?

public class MyClass
{
    public string _datafile;

    public MyClass()
    {
        _datafile = "Hello";
    }

    public void PrintField()
    {
        var result = this.GetType().GetField("_datafile").GetValue(this); 
        Console.WriteLine(result); // will print Hello
    }
}

EDIT: @Rick, to respond to your comment:

public class MyClass
{
    public IEnumerable<string> _parameters = new[] { "Val1", "Val2", "Val3" };

    public void PrintField()
    {
        var parameters = this.GetType().GetField("_parameters").GetValue(this) as IEnumerable;

        // Prints:
        // Val1
        // Val2
        // Val3
        foreach(var item in parameters)
        {
            Console.WriteLine(item);
        }
    }
}

If you want to get the value of a field based on its string name you will have to use reflection.

class MyClass
{
    public int DataFile { get; set; }

    public int _datafile;
}

var ob = new MyClass();
var typ = typeof(MyClass);
var f = typ.GetField("_datafile");
var prop = typ.GetProperty("DataFile");
var val = f.GetValue(ob);
var propVal = prop.GetValue(ob);

Usually you would create a class representing the values of one table record. If your table has an ID a FirstName and a LastName column, you would create a class like this

public class Person
{
    public int ID { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

Then you create a list of persons

var people = new List<Person>();

Now you can add persons to the list.

var p = new Person();
p.ID = 5;
p.FirstName = "John";
p.LastName = "Doe";
people.Add(p);

You can use a DataReader in order to read from a table

string sql = "SELECT * FROM tblPerson WHERE LastName LIKE @pattern";
cmd = new SqlCommand(sql);
cmd.Connection = "server=test;uid=sa;pwd=manager;database=northwind";
cmd.Parameters.AddWithValue("@pattern", "A%"); // Names beginning with "A"
using (SqlDataReader reader = cmd.ExecuteReader()) {
    // Get column indexes
    int idOrdinal = reader.GetOrdinal("ID");
    int firstNameOrdinal = reader.GetOrdinal("FirstName");
    int lastNameOrdinal = reader.GetOrdinal("LastName");

    while(reader.Read()) {
        var p = new Person();
        p.ID = reader.GetInt32(idOrdinal);
        p.FirstName = reader.GetString(firstNameOrdinal);
        p.LastName = reader.GetString(lastNameOrdinal);
        people.Add(p);
    }
}