Concise usage of DBNull? (Ternary?)

Question

Hey all,

It seems that there's some type confusion in the ternary operator. I know that this has been addressed in other SO threads, but it's always been with nullables. Also, for my case I'm really just looking for a better way.

I'd like to be able to use

proc.Parameters[PARAM_ID].Value = 
    string.IsNullOrEmpty(dest.Id) ? DBNull.Value : dest.Id;

but instead I'm stuck with this:

if (string.IsNullOrEmpty(dest.Id))
{
    proc.Parameters[PARAM_ID].Value = DBNull.Value;
}
else
{
    proc.Parameters[PARAM_ID].Value = dest.Id;
} 

The ternary operator fails because there's no conversion possible between DBNull and string, and as silly as that seems considering Value is object, the compiler kicks it back to me and I'm forced to care. The answer to the nullable version of this question is to just cast null to string and be done with it; DBNull can't be cast to string, though, so no luck there.

Is there a more concise way to do this (without using nullables, by the way?)

Thanks!

Answer 1

The Value property is of type object, so you should cast to object, not string:

proc.Parameters[PARAM_ID].Value = string.IsNullOrEmpty(dest.Id)
    ? (object)DBNull.Value
    : (object)dest.Id;

Answer 2

You could change your first statement to:

proc.Parameters[PARAM_ID].Value = 
    string.IsNullOrEmpty(dest.Id) ? (object)DBNull.Value : dest.Id;

Answer 3

Or you could add an extension method such as:

public static class DBNullExtensions
{
    public static object AsDBNullIfEmpty(this string value)
    {
        if (String.IsNullOrEmpty(value))
        {
            return DBNull.Value;
        }
        return value;
    }
}

And then you could just say

proc.Parameters[PARAM_ID].Value = dest.Id.AsDBNullIfEmpty();

(Adapted from Phil Haack)

Readable and concise, no?