Question

What alternatives are there to property.setvalue()? I’ve read that it is very slow. I’m using it to map IDataReader to POCO objects.

This is a truncated version of the code. Everything here is very new to me. I know there a lot of frameworks that accomplish this task. However, we can’t use them.

public class DbAutoMapper<T>
{
    public IEnumerable<T> MapToList(IDataReader reader)
    {
        var list = new List<T>();

        while (reader.Read())
        {                
            var obj = Activator.CreateInstance<T>();

            foreach (PropertyInfo prop in obj.GetType().GetProperties())
            {
                foreach (var attribute in prop.GetCustomAttributes(true))
                {                        
                    prop.SetValue(obj, value, null);                        
                }
            }

            list.Add(obj);
        }
        return list;
    }
}

Answer 1

Firstly: why are you repeating the reflection for every attribute, when you don’t use the attribute?

Second: assuming you intended to map this by name, column-to-property (which isn’t what the code currently does), consider a tool like dapper, which does all this for you, including cached high-performance reflection-emit. It’ll also handle the command itself for you. For example:

string region = "North";
var customers = conn.Query<Customer>(
    @"select * from Customers where Region = @region",
    new { region } // full parameterization, the easy way
).ToList();

If you need more control, consider FastMember, which provides fast member-access (again, reflection-emit), but without being specific to data access:

var accessor = TypeAccessor.Create(typeof(T)); 
string propName = // something known only at runtime 
while( /* some loop of data */ ) {
    var obj = new T();
    foreach(var col in cols) {
        string propName = // ...
        object cellValue = // ...
        accessor[obj, propName] = cellValue;
    }
    yield return obj;
}