Nullable objects must have value error

Question

I've seen this question posted a number of times here but I don't think I understand the solution as it related to my problem.

I'm getting the exception on this line:

return CurrentCompany.ParentCompanyId == null 
    ? (Guid)CurrentCompany.ParentCompanyId 
    : CurrentCompanyID;

Here's more of the code:

/// Return the current company id, unless this is a child company id, 
/// then return the parent company id.
private Guid MainCompanyID
{
    get
    {
        return CurrentCompany.ParentCompanyId == null 
            ? (Guid)CurrentCompany.ParentCompanyId 
            : CurrentCompanyID;
    }
}

I'm happy to share more if needed but this is about the extent of the stack trace.

Your condition is the wrong way round and should be != instead of == null. You could also use the null coalescing operator instead: return CurrentCompany.ParentCompanyId ?? CurrentCompanyID. — Lee
– Lee, Commented Oct 1, 2013 at 19:10

Khan · Accepted Answer · 2013-10-01 19:19:01Z

4

You're using ParentCompanyId after you've confirmed that it is null.
You want to use CurrentCompanyID in that case.

This:

return CurrentCompany.ParentCompanyId == null 
    ? (Guid)CurrentCompany.ParentCompanyId : CurrentCompanyID;

Should be this:

return CurrentCompany.ParentCompanyId != null 
    ? (Guid)CurrentCompany.ParentCompanyId : CurrentCompanyID;

Notice == is now !=. You essentially just want to reverse the condition.

edited Oct 1, 2013 at 19:19

answered Oct 1, 2013 at 19:07

Khan

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Comments

Indi · Accepted Answer · 2013-10-01 19:19:41Z

1

Since your CurrentCompany.ParentCompanyId is nullable, you could also use null-coalescing operator -?? as below.

private Guid MainCompanyID
{
    get
    {
        return (Guid)(CurrentCompany.ParentCompanyId ?? CurrentCompanyID);
    }
}

answered Oct 1, 2013 at 19:19

Indi

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Comments

Sriram Sakthivel · Accepted Answer · 2013-10-01 19:29:31Z

1

You're checking for null and using it. It should be !=

private Guid MainCompanyID
{
    get
    {
        return CurrentCompany.ParentCompanyId != null ? (Guid)CurrentCompany.ParentCompanyId : CurrentCompanyID;
    }
}

This could be easily re written as the following using null collaescing operator ?? (If parentId is Guid? and CurrentCompanyID is Guid)

private Guid MainCompanyID
{
    get
    {
        return CurrentCompany.ParentCompanyId ?? CurrentCompanyID;
    }
}

edited Oct 1, 2013 at 19:29

answered Oct 1, 2013 at 19:09

Sriram Sakthivel

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System Down · Accepted Answer · 2013-10-01 19:09:12Z

0

You have a problem in your ternary operator. This line:

return CurrentCompany.ParentCompanyId == null ? (Guid)CurrentCompany.ParentCompanyId : CurrentCompanyID;

Basically translates to:

if (CurrentCompany.ParentCompanyId == null) 
    return (Guid)CurrentCompany.ParentCompanyId
else
    return CurrentCompanyID;

So the problem is that you are trying to cast a null into a Guid here. You need to reverse your condition:

return CurrentCompany.ParentCompanyId != null ? (Guid)CurrentCompany.ParentCompanyId : CurrentCompanyID;

answered Oct 1, 2013 at 19:09

System Down

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Comments

User · Accepted Answer · 2013-10-01 19:26:40Z

The ? Operator is easiest shortened to:

booleanValue ? resultIfTrue : resultIfFalse;

Where both the true and false results must by of the same type.

Looking at your code:

CurrentCompany.ParentCompanyId == null         //booleanValue
        ? (Guid)CurrentCompany.ParentCompanyId //resultIfTrue
        : CurrentCompanyID;                    //resultIfFalse

This means you are attempting to return the ParentCompanyId when you've already verified it is null. I'm guessing you wanted to do the opposite. To do so, You'll want to change your boolean expression to check for not null:

CurrentCompany.ParentCompanyId != null         //booleanValue
        ? (Guid)CurrentCompany.ParentCompanyId //resultIfTrue
        : CurrentCompanyID;                    //resultIfFalse

Or, you could leave the boolean expression as is and switch the order of the return values:

CurrentCompany.ParentCompanyId == null         //booleanValue
        ? CurrentCompanyID                     //resultIfTrue
        : (Guid)CurrentCompany.ParentCompanyId;//resultIfFalse

Either should work fine.

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