Creating Dynamic Objects

Question

How to dynamically create objects?

string[] columnNames = { "EmpName", "EmpID", "PhoneNo" };
List<string[]> columnValues = new List<string[]>();
for (int i = 0; i < 10; i++)
{
    columnValues.Add(new[] { "Ramesh", "12345", "12345" });
}

List<Dictionary<string, object>> testData = new List<Dictionary<string, object>>();

foreach (string[] columnValue in columnValues)
{
    Dictionary<string, object> data = new Dictionary<string, object>();
    for (int j = 0; j < columnNames.Count(); j++)
    {
        data.Add(columnNames[j], columnValues[j]);
    }
    testData.Add(data);
}

Imaginary Class(Class is not available in code):

class Employee
{
    string EmpName { get;set; }
    string EmpID { get;set; }
    string PhoneNo { get;set; }
}

Note: Property/column names are dynamic.

Now I want to convert the List<Dictionary<string, object>> to a class of type List<object> (i.e) List<Employee>.

Is it Possible? Suggestions please.

Answer 1

Using an anonymous object (if you know the properties you want to project):

var employees = 
    (from dict in testData 
        select new 
        { 
            EmpName = dict["EmpName"] as string, 
            EmpID= dict["EmpID"] as string, 
            PhoneNo=dict["PhoneNo"] as string 
        }).ToList();

Or, using System.Dynamic.Expando (if you need to dynamically project unknown column names):

string[] columnNames = { "EmpName", "EmpID", "PhoneNo" };
List<string[]> columnValues = new List<string[]>();
for (int i = 0; i < 10; i++)
{
    columnValues.Add(new[] { "Ramesh", "12345", "12345" });
}

var testData = new List<ExpandoObject>();

foreach (string[] columnValue in columnValues)
{
    dynamic data = new ExpandoObject();
    for (int j = 0; j < columnNames.Count(); j++)
    {
        ((IDictionary<String,Object>)data).Add(columnNames[j], columnValue[j]);
    }
    testData.Add(data);
}

Answer 2

Edited to suggest "Emit".

In light of the fact that you don't even know the column names, I would use Reflection.Emit to first create the Employee class on the fly. See http://msdn.microsoft.com/en-us/library/3y322t50(v=vs.100).aspx for information on how to use Emit. The pseudo code will then be:

ReflectionEmit("Employee", columns);
List<object> newList = testData.Select<object>(p => {
    var employee = ReflectionInstantiate("Employee");
    foreach column in columns
         Reflection.SetProperty(employee, column, p[column]);
    });

The real code will be a little more complicated as Emit is not straightforward. :)