C# – How does Entity Framework work with recursive hierarchies? Include() seems not to work with it

centity-frameworkvisual-studio-2008

I have an Item. Item has a Category.

Category has ID, Name, Parent and Children. Parent and Children are of Category too.

When I do a LINQ to Entities query for a specific Item, it doesn't return the related Category, unless I use the Include("Category") method. But it doesn't bring the full category, with its parent and children. I could do Include("Category.Parent"), but this object is something like a tree, I have a recursive hierarchy and I don't know where it ends.

How can I make EF fully load the Category, with parent and children, and the parent with their parent and children, and so on?

This is not something for the whole application, for performance considerations it would be needed only for this specific entity, the Category.

Best Answer

Instead of using the Include method you could use Load.

You could then do a for each and loop through all the children, loading their children. Then do a for each through their children, and so on.

The number of levels down you go will be hard coded in the number of for each loops you have.

Here is an example of using Load: http://msdn.microsoft.com/en-us/library/bb896249.aspx

Related Solutions

.net – Entity Framework vs LINQ to SQL

LINQ to SQL only supports 1 to 1 mapping of database tables, views, sprocs and functions available in Microsoft SQL Server. It's a great API to use for quick data access construction to relatively well designed SQL Server databases. LINQ2SQL was first released with C# 3.0 and .Net Framework 3.5.

LINQ to Entities (ADO.Net Entity Framework) is an ORM (Object Relational Mapper) API which allows for a broad definition of object domain models and their relationships to many different ADO.Net data providers. As such, you can mix and match a number of different database vendors, application servers or protocols to design an aggregated mash-up of objects which are constructed from a variety of tables, sources, services, etc. ADO.Net Framework was released with the .Net Framework 3.5 SP1.

This is a good introductory article on MSDN: Introducing LINQ to Relational Data

C# – Case insensitive ‘Contains(string)’

You could use the String.IndexOf Method and pass StringComparison.OrdinalIgnoreCase as the type of search to use:

string title = "STRING";
bool contains = title.IndexOf("string", StringComparison.OrdinalIgnoreCase) >= 0;

Even better is defining a new extension method for string:

public static class StringExtensions
{
    public static bool Contains(this string source, string toCheck, StringComparison comp)
    {
        return source?.IndexOf(toCheck, comp) >= 0;
    }
}

Note, that null propagation ?. is available since C# 6.0 (VS 2015), for older versions use

if (source == null) return false;
return source.IndexOf(toCheck, comp) >= 0;

USAGE:

string title = "STRING";
bool contains = title.Contains("string", StringComparison.OrdinalIgnoreCase);

Best Answer

Related Solutions

.net – Entity Framework vs LINQ to SQL

C# – Case insensitive ‘Contains(string)’

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