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How to check null value in linq on sql

I am trying to use the following linq to sql query to get the result. But this does not work if parentCategoryId is passed as null

 public static IEnumerable<Category> GetChildren(this Table<Category> source, int? parentCategoryId)
    {
        var categories = from c in source where c.ParenCategoryId == parentCategoryId select c;
        return categories;
    }

but after work, if null is used directly instead of parentCategoryId

 public static IEnumerable<Category> GetChildren(this Table<Category> source, int? parentCategoryId)
    {
        var categories = from c in source where c.ParenCategoryId == null select c;
        return categories;
    }
+5
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2 answers

You can use object.Equals, it will also match the values null.

public static IEnumerable<Category> GetChildren(this Table<Category> source, int? parentCategoryId)
{
    var categories = from c in source 
                     where object.Equals(c.ParenCategoryId, parentCategoryId) 
                     select c;
    return categories;
}
+8
source

You can try the following

public static IEnumerable<Category> GetChildren(this Table<Category> source, int? parentCategoryId)
{
    var categories = from c in source 
                     where (parentCategoryId != null? c.ParenCategoryId == parentCategoryId : c.ParenCategoryId == null)
                     select c;
    return categories;
}
0
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