In this article I am going to discuss about how to get distinct object using property  of it from collection. Here I am going to show three different way to achieve it easily.
In this post I am going to discuss about extension method that can do task more than the current Distinct method available in .Net framework.

Distinct method of Linq works as following right now. 

public class Product
{
    public string Name { get; set; }
    public int Code { get; set; }
}

Consider that we have product Class which is having Code and Name as property in it.
Now Requirement is I have to find out the all product with distinct Code values.

Product[] products = { new Product { Name = "apple", Code = 9 }, 
                       new Product { Name = "orange", Code = 4 }, 
                       new Product { Name = "apple", Code = 10 }, 
                       new Product { Name = "lemon", Code = 9 } };
var lstDistProduct = products.Distinct();
foreach (Product p in list1)
{
     Console.WriteLine(p.Code + " : " + p.Name);
}

Output

It returns all the product event though two product have same Code value. So this doesn't meet requirement of getting object with distinct Code value.

Way 1 : Make use of MoreLinq Library
First way to achieve the requirement is make use of MoreLinq Library, which support function called DistinctBy in which you can specify the property on which you want to find Distinct objects.
Below code is shows the use of the function.

var list1 = products.DistinctBy(x=> x.Code);




foreach (Product p in list1)
{
     Console.WriteLine(p.Code + " : " + p.Name);
}

Output

As  you can see in output there is only two object get return which actually I want. i.e. distinct value by Code or product.
If you want to pass more than on property than you can just do like this  var list1 = products.DistinctBy(a => new { a.Name, a.Code });
You can read about the MoreLinq and Download this DLL from here : http://code.google.com/p/morelinq/ one more thing about this library also contains number of other function that you can check.

Way 2: Implement Comparable
Second way to achieve the same functionality is make use of overload Distinct function which support to have comparator as argument.
here is MSDN documentation on this : Enumerable.Distinct<TSource> Method (IEnumerable<TSource>, IEqualityComparer<TSource>)

So for that I implemented IEqualityComparer and created new ProductComparare which you can see in below code.

    class ProductComparare : IEqualityComparer<product>
    {
        private Func<Product, object> _funcDistinct;
        public ProductComparare(Func<Product, object> funcDistinct)
        {
            this._funcDistinct = funcDistinct;
        }




        public bool Equals(Product x, Product y)
        {
            return _funcDistinct(x).Equals(_funcDistinct(y));
        }




        public int GetHashCode(Product obj)
        {
            return this._funcDistinct(obj).GetHashCode();
        }
    }
</product>