Entity Framework: check if object exists and check if it has an associated object

Question

In a many-to-many relationship between File and Category I want to check if a file exists and if so, if it has any categories (because there's a chance it may not have any) :

        public bool existsInDBAndHasCategories(string path)
    {
        using (WinFileContextContainer c = new WinFileContextContainer())
        {
            return c.File.Any((o => o.path == path));
        }
    }

This checks if a file with this path has a record in the database. I got this from a thread on this site. Truth be told I am still not good with LINQ and lambdas, so I don't know how to extend it to give me BOOLEAN for any categories as well. Thanks in advance for the time.

score 1 · Accepted Answer · answered May 21 '13 at 07:53

1

You just have to add another condition to your method (Assuming you have defined Categories as a list of Category in File class) :

return c.File.Any((o => o.path == path && o.Categories.Any()));

answered May 21 '13 at 07:53

Kamyar

18,639
9
97
171

score 0 · Answer 2 · answered May 21 '13 at 07:54

If you are not familiar with Lamba, start learning simple LinQ, before you move on to lambda inside Linq queries.

You code shoud be like this:

public bool existsInDBAndHasCategories(string path)
{
    using (WinFileContextContainer c = new WinFileContextContainer())
    {
        var query = from f in c.File
            where f.Path == path &&
            (f.Categories != null || f.Categories.Count != 0)
            select f;
        return (f.Count != 0)
    }
}

Entity Framework: check if object exists and check if it has an associated object

2 Answers2