Using Reflection to create a DataTable from a Class?

Question

I\'ve just learned about Generics and I\'m wondering whether I can use it to dynamically build datatables from my classes.

Or I might be missing the point here. Here

Answer 1

The error can be resolved by changing this:

dogTable = CreateDataTable(Dog);

to this:

dogTable = CreateDataTable(typeof(Dog));

But there are some caveats with what you're trying to do. First, a DataTable can't store complex types, so if Dog has an instance of Cat on it, you won't be able to add that as a column. It's up to you what you want to do in that case, but keep it in mind.

Second, I would recommend that the only time you use a DataTable is when you're building code that knows nothing about the data its consuming. There are valid use cases for this (e.g. a user-driven data mining tool). If you already have the data in the Dog instance, just use it.

Another little tidbit, this:

DataTable dogTable = new DataTable();
dogTable = CreateDataTable(Dog);

can be condensed to this:

DataTable dogTable = CreateDataTable(Dog);

Answer 2

you can convert the object to xml then load the xml document to a dataset, then extract the first table out of the data set. However i dont see how this be practical as it infers creating streams, datasets & datatables and using converstions to create the xml document.

I guess for proof of concept i can understand why. Here is an example, but somewhat hesitant to use it.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.Data;
using System.Xml.Serialization;

namespace Generics
{
public class Dog
{
    public string Breed { get; set; }
    public string Name { get; set; }
    public int legs { get; set; }
    public bool tail { get; set; }
}

class Program
{
    public static DataTable CreateDataTable(Object[] arr)
    {
        XmlSerializer serializer = new XmlSerializer(arr.GetType());
        System.IO.StringWriter sw = new System.IO.StringWriter();
        serializer.Serialize(sw, arr);
        System.Data.DataSet ds = new System.Data.DataSet();
        System.Data.DataTable dt = new System.Data.DataTable();
        System.IO.StringReader reader = new System.IO.StringReader(sw.ToString());

        ds.ReadXml(reader);
        return ds.Tables[0];
    }

    static void Main(string[] args)
    {
        Dog Killer = new Dog();
        Killer.Breed = "Maltese Poodle";
        Killer.legs = 3;
        Killer.tail = false;
        Killer.Name = "Killer";

        Dog [] array_dog = new Dog[5];
        Dog [0] = killer;
        Dog [1] = killer;
        Dog [2] = killer;
        Dog [3] = killer;
        Dog [4] = killer;

        DataTable dogTable = new DataTable();
        dogTable = CreateDataTable(array_dog);

        // continue here

        }      
    }
}

look the following example here

Answer 3

If you want to set columns order/ Include only some columns/ exclude some columns try this:

        private static DataTable ConvertToDataTable<T>(IList<T> data, string[] fieldsToInclude = null,
string[] fieldsToExclude = null)
    {
        PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(typeof(T));
        DataTable table = new DataTable();
        foreach (PropertyDescriptor prop in properties)
        {
            if ((fieldsToInclude != null && !fieldsToInclude.Contains(prop.Name)) ||
                (fieldsToExclude != null && fieldsToExclude.Contains(prop.Name)))
                continue;
            table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
        }

        foreach (T item in data)
        {
            var atLeastOnePropertyExists = false;
            DataRow row = table.NewRow();
            foreach (PropertyDescriptor prop in properties)
            {

                if ((fieldsToInclude != null && !fieldsToInclude.Contains(prop.Name)) ||
(fieldsToExclude != null && fieldsToExclude.Contains(prop.Name)))
                    continue;

                row[prop.Name] = prop.GetValue(item) ?? DBNull.Value;
                atLeastOnePropertyExists = true;
            }

            if(atLeastOnePropertyExists) table.Rows.Add(row);
        }


        if (fieldsToInclude != null)
            SetColumnsOrder(table, fieldsToInclude);

        return table;

    }

    private static void SetColumnsOrder(DataTable table, params String[] columnNames)
    {
        int columnIndex = 0;
        foreach (var columnName in columnNames)
        {
            table.Columns[columnName].SetOrdinal(columnIndex);
            columnIndex++;
        }
    }