Question

Hi i try to get some Date from my Database but it wont work and i really have no Idea why.

I get following Error:

Error: Entities in 'DataBase' participate in the 'FK_MSCourse_Language' relationship. 0 related 'Language' were found. 1 'Language' is expected. 

My Code:

var language = db.Language.Where(x => x.Designation == publicLanguage);

if (language != null)
{
  newCourse.Language = language.SingleOrDefault();
}
else
{
  newCourse.Language = db.Language.SingleOrDefault(x => x.Designation == "English");
}

If i do it this way it works, but i want to have it dynamically to Languages from the DataBase.

switch (publicLanguage)
{
  case "French":
    newCourse.Language = db.Language.SingleOrDefault(x => x.Designation == "French");
    break;
  default:
    newCourse.Language = db.Language.SingleOrDefault(x => x.Designation == "English");
    break;
}

Anyone knows what i am doing wrong?

Thanks,
Markus

Answer 1

LINQ’s Where operation returns an IEnumerable, which can never be null, making your if block useless. It will always execute newCourse.Language = language.SingleOrDefault(); no matter what.

I’m also thinking that trying to use == on what is most likely a string variable could be causing you some problems also. I would recommend using the .Equals() method instead, which will actually investigate if the strings are equal. Also, since you’re just trying to grab the first one, why not just do this:

var language = db.Language.FirstOrDefault(x => x.Designation.Equals(publicLanguage));

This will grab the first one that matches that language, or return null. In such a case, then you can just have an if statement which will then assign English as the language if the language variable is, in fact, null.