Linq: Nullable Object must have Value

Don Thomas Boyle Published at Dev

Don Thomas Boyle

My query is as follows:

int ID = db.Q_Table.Find(item.PassedInID).ID;

I already found a solution for my issue, however i am wondering why i must write it like so

Nullable(int) ID = db.Q_Table.Find(item.PassedInID).ID;

db.Q_Table.Where(w => w.PassedInID== item.PassedInID).Select(s => s.ID ).SingleOrDefault();

It wouldn't let me put int int he < in the above code -.-...

I am curious why i have to code it to a nullable int? I really didn't want to code it like 2nd solution because its more code :). Yes i have made sure there are values in the database and from the below image you can see my database doesn't accept nulls.

Thanks for any answers

enter image description here

Habib

There is a difference between int and Nullable<int> or int?, you can't directly assign a Nullable<int> to int (Nullable<T>), Consider:

int? x = 123;
int y = x; //This would be an error

But you can use null-coalescing operator

int? x = 123;
int y = x ?? 0;

Now for your case, your ID seems to be a mapped to column in database which allows null. That will map to C# Nullable<int>, if you want to assign the result to an int you can do:

int ID = db.Q_Table.Find(item.PassedInID).ID ?? 0;

That will give your variable the value of ID or 0 if it is null.

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edited at2021-02-6

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