LINQ check if exists, but without equal to any value

use FirstOrDefault(), it is just like First() except that if no element match the specified condition than it returns the default value of the underlying type of generic collection.

You can then check if the value is defined which tells you if any items exist in the database, in your case FirstOrDefault() will return null if no images exist in the database.

You can also use Any() with First() as well

My solution would be

var images = productImageRepository.Get().Where(i => i.ProductId == productId).OrderBy(i => i.Position);
if (images.Any()) {
    // could just use First() here now if you wanted 
    // as Any() confirms there is values defined
    return Json(images.FirstOrDefault());
} else {
   // throw a error or something. 
}