扩展方法甚至在实现IEnumerable时也未显示

Question

This is my code:

    class myClass : IEnumerable
    {
        public Dictionary<int, string> dctIdName = new Dictionary<int, string>();

        public myClass()
        {
            for (int idx = 0; idx < 100; idx++)
            {
                dctIdName.Add(idx, string.Format("Item{0}", idx));
            }

        }

        // IEnumerable Member
        public IEnumerator GetEnumerator()
        {
            foreach (object o in dctIdName)
            {
                yield return o;
            }
        }
    }

Where i create an object of this class and use it in this manner i do not get the LINQ extension methods like Where , Count , etc.

myClass obj = new myClass();
var d = obj.Where( x => x.Key == 10); //<-- Error here

The namespaces i have included are:

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Xml.Linq;

How to fix this?

Answer 1

It does work. AsParallel is an extension method on IEnumerable . Most extension methods though work on IEnumerable<T> . Your class should start with this:

class myClass : IEnumerable<SomeType>

Or:

class myClass<T> : IEnumerable<T>

(Where T is the type of the generic type argument)

---

class myClass : IEnumerable<KeyValuePair<int, string>>
{
    public Dictionary<int, string> dctIdName = new Dictionary<int, string>();

    public myClass()
    {
        for (int idx = 0; idx < 100; idx++)
        {
            dctIdName.Add(idx, string.Format("Item{0}", idx));
        }

    }

    // IEnumerable Member
    public IEnumerator<KeyValuePair<int, string>> GetEnumerator()
    {
        foreach (KeyValuePair<int, string> o in dctIdName)
        {
            yield return o;
        }
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return this.GetEnumerator();
    }
}

Now you can call Select for example.

Answer 2

You need to implement the generic version of IEnumerable. I guess in your case it would be:

IEnumerable<KeyValuePair<int, string>>

or

IEnumerable<object>

Answer 3

Only the following extension methods are defined by the .NET Framework for IEnumerable

AsParallel() - Enables parallelization of a query.(Defined by ParallelEnumerable.)

AsQueryable() - Converts an IEnumerable to an IQueryable.(Defined by Queryable.)

Cast() - Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.)

OfType() - Filters the elements of an IEnumerable based on a specified type.(Defined by Enumerable.)

IEnumerable<T> is what you are looking for.