Question

I am attempting to create a Dictionary from my DataTable. Currently i do this by first creating a IList and then looping through the List and adding them to a dictionary individually specifying the Primary key property of the resulting object in the list on a case by case basis.

I was wondering if this could be done using generics.

Ive currently got the following code, which doesnt compile or work:

public static IDictionary<T1, T2> ToDictionary<T1,T2>(this DataTable table) where T2 : new()
{
    IList<PropertyInfo> properties = GetPropertiesForType<T2>();
    IDictionary<T1,T2> result = new Dictionary<T1,T2>();
    Dictionary<string, int> propDict = GetPropertyDictionary(properties, table);
    T1 PK;
    foreach (var row in table.Rows)
    {
        var item = CreateDictItemFromRow<T2>((DataRow)row, properties, propDict);
        result.Add(item. item); //not sure here
    }
    return result;
}

Essentially i would like to call the following:

Dictionary<int, MyDBClass> Items = DataTable.ToDictionary<int,MyDBClass>();

or

Dictionary<Int16,MyDBClass> Items = DataTable.ToDictionary<Int16, MyDBClass>();

Im assuming somewhere i need to pass the primary key property name to this function. Failing that i can safely assume the first column in my Datatable contains the primary key (although its not safe to assume it is always an int (it maybe a short or byte)).

I also understand this could quite easily be done using LINQ, but i havent got that far in C# and wish to alter existing application.

Help is appreciated.

Answer 1

Hope this helps.

        public static class Extensions
        {
            public static Dictionary<TKey, TRow> TableToDictionary<TKey,TRow>(
                this DataTable table,
                Func<DataRow, TKey> getKey,
                Func<DataRow, TRow> getRow)
            {
                return table
                    .Rows
                    .OfType<DataRow>()
                    .ToDictionary(getKey, getRow);
            }
        }



        public static void SampleUsage()
        {
            DataTable t = new DataTable();

            var dictionary = t.TableToDictionary(
                row => row.Field<int>("ID"),
                row => new {
                    Age = row.Field<int>("Age"),
                    Name = row.Field<string>("Name"),
                    Address = row.Field<string>("Address"),
                });
        }

By the way, you need to include the assembly, System.Data.DataSetExtensions.dll, to use the Field extension method.

If you have any other questions, don’t hesitate to ask.