arcgis 10.0 - Null values in plugin data source

How do you appropriately setup a plugin data source to allow for null values (in .NET - C# preferred)?

I'm currently setting up a field using:

field.Type_2 = esriFieldType.esriFieldTypeSingle;
field.IsNullable_2 = true;
field.Name_2 = "Foo";

Then, later, during the cursor's QueryValues call, I'm trying to set a null value via:

// Given: public int QueryValues(IRowBuffer row)

row.Value[i] = null;

However, the value always maps through as 0, not null. How do you properly setup the data source in a plugin data source to allow for a null value?

Answer

Have you tried setting DBNull.Value instead of null?